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freebsd-skq/sys/kern/sched_ule.c

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- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
/*-
sys/kern: adoption of SPDX licensing ID tags. Mainly focus on files that use BSD 2-Clause license, however the tool I was using misidentified many licenses so this was mostly a manual - error prone - task. The Software Package Data Exchange (SPDX) group provides a specification to make it easier for automated tools to detect and summarize well known opensource licenses. We are gradually adopting the specification, noting that the tags are considered only advisory and do not, in any way, superceed or replace the license texts.
2017-11-27 15:20:12 +00:00
* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
*
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
* Copyright (c) 2002-2007, Jeffrey Roberson <jeff@freebsd.org>
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice unmodified, this list of conditions, and the following
* disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* This file implements the ULE scheduler. ULE supports independent CPU
* run queues and fine grain locking. It has superior interactive
* performance under load even on uni-processor systems.
*
* etymology:
- Improve grammar. s/it's/its/. - Improve load long-term load balancer by always IPIing exactly once. Previously the delay after rebalancing could cause problems with uneven workloads. - Allow nice to have a linear effect on the interactivity score. This allows negatively niced programs to stay interactive longer. It may be useful with very expensive Xorg servers under high loads. In general it should not be necessary to alter the nice level to improve interactive response. We may also want to consider never allowing positively niced processes to become interactive at all. - Initialize ccpu to 0 rather than 0.0. The decimal point was leftover from when the code was copied from 4bsd. ccpu is 0 in ULE because ULE only exports weighted cpu values. Reported by: Steve Kargl (Load balancing problem) Approved by: re
2007-09-22 02:20:14 +00:00
* ULE is the last three letters in schedule. It owes its name to a
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
* generic user created for a scheduling system by Paul Mikesell at
* Isilon Systems and a general lack of creativity on the part of the author.
*/
Use __FBSDID().
2003-06-11 00:56:59 +00:00
#include <sys/cdefs.h>
- Fix the FBSDID line.
2009-04-29 03:26:30 +00:00
__FBSDID("$FreeBSD$");
Use __FBSDID().
2003-06-11 00:56:59 +00:00
Move HWPMC_HOOKS into its own opt_hwpmc_hooks.h file. It doesn't merit being in opt_global.h and forcing a global recompile when only a few files reference it. Approved by: re
2005-06-24 00:16:57 +00:00
#include "opt_hwpmc_hooks.h"
#include "opt_sched.h"
Turn PREEMPTION into a kernel option. Make sure that it's defined if FULL_PREEMPTION is defined. Add a runtime warning to ULE if PREEMPTION is enabled (code inspired by the PREEMPTION warning in kern_switch.c). This is a possible MT5 candidate.
2004-09-02 18:59:15 +00:00
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
#include <sys/param.h>
#include <sys/systm.h>
Update for the KDB framework: o Call kdb_backtrace() instead of backtrace().
2004-07-10 21:38:22 +00:00
#include <sys/kdb.h>
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
#include <sys/kernel.h>
#include <sys/ktr.h>
Fix GENERIC build.
2014-03-19 00:38:27 +00:00
#include <sys/limits.h>
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/proc.h>
- Add in support for KSEs with 0 slice values on the run queue. If we try to select a KSE with a slice of 0 we will update its slice and insert it onto the next queue. - Pass the KSE instead of the ksegrp into sched_slice(). This more accurately reflects the behavior of the code. Slices are granted to kses. - Add a function kseq_nice_min() which finds the smallest nice value assigned to the kseg of any KSE on the queue. - Rewrite the logic in sched_slice(). Add a large comment describing the new slice selection scheme. To summarize, slices are assigned based on the nice value. Priorities are still calculated based on the nice and interactivity of a process. Slice sizes of 0 may be granted for KSEs whos nice is 20 or futher away from the lowest nice on the run queue. Other nice values are scaled across the range [min, min+20]. This fixes ULEs bad behavior with positively niced processes.
2003-04-02 06:46:43 +00:00
#include <sys/resource.h>
- Add initial support for pinning and binding.
2003-11-04 07:45:41 +00:00
#include <sys/resourcevar.h>
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
#include <sys/sched.h>
Implement the DTrace sched provider. This implementation aims to be compatible with the sched provider implemented by Solaris and its open- source derivatives. Full documentation of the sched provider can be found on Oracle's DTrace wiki pages. Note that for compatibility with scripts originally written for Solaris, serveral probes are defined that will never fire. These probes are defined to fire when Solaris-specific features perform certain actions. As these features are not present in FreeBSD, the probes can never fire. Also, I have added a two probes that are not defined in Solaris, lend-pri and load-change. These probes have been added to make it possible to collect schedgraph data with DTrace. Finally, a few probes are defined in Solaris to take a cpuinfo_t * argument. As it was not immediately clear to me how to translate that to FreeBSD, currently those probes are passed NULL in place of a cpuinfo_t *. Sponsored by: Sandvine Incorporated MFC after: 2 weeks
2012-05-15 01:30:25 +00:00
#include <sys/sdt.h>
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
#include <sys/smp.h>
#include <sys/sx.h>
#include <sys/sysctl.h>
#include <sys/sysproto.h>
Rework the interface between priority propagation (lending) and the schedulers a bit to ensure more correct handling of priorities and fewer priority inversions: - Add two functions to the sched(9) API to handle priority lending: sched_lend_prio() and sched_unlend_prio(). The turnstile code uses these functions to ask the scheduler to lend a thread a set priority and to tell the scheduler when it thinks it is ok for a thread to stop borrowing priority. The unlend case is slightly complex in that the turnstile code tells the scheduler what the minimum priority of the thread needs to be to satisfy the requirements of any other threads blocked on locks owned by the thread in question. The scheduler then decides where the thread can go back to normal mode (if it's normal priority is high enough to satisfy the pending lock requests) or it it should continue to use the priority specified to the sched_unlend_prio() call. This involves adding a new per-thread flag TDF_BORROWING that replaces the ULE-only kse flag for priority elevation. - Schedulers now refuse to lower the priority of a thread that is currently borrowing another therad's priority. - If a scheduler changes the priority of a thread that is currently sitting on a turnstile, it will call a new function turnstile_adjust() to inform the turnstile code of the change. This function resorts the thread on the priority list of the turnstile if needed, and if the thread ends up at the head of the list (due to having the highest priority) and its priority was raised, then it will propagate that new priority to the owner of the lock it is blocked on. Some additional fixes specific to the 4BSD scheduler include: - Common code for updating the priority of a thread when the user priority of its associated kse group has been consolidated in a new static function resetpriority_thread(). One change to this function is that it will now only adjust the priority of a thread if it already has a time sharing priority, thus preserving any boosts from a tsleep() until the thread returns to userland. Also, resetpriority() no longer calls maybe_resched() on each thread in the group. Instead, the code calling resetpriority() is responsible for calling resetpriority_thread() on any threads that need to be updated. - schedcpu() now uses resetpriority_thread() instead of just calling sched_prio() directly after it updates a kse group's user priority. - sched_clock() now uses resetpriority_thread() rather than writing directly to td_priority. - sched_nice() now updates all the priorities of the threads after the group priority has been adjusted. Discussed with: bde Reviewed by: ups, jeffr Tested on: 4bsd, ule Tested on: i386, alpha, sparc64
2004-12-30 20:52:44 +00:00
#include <sys/turnstile.h>
Add user priority loaning code to support priority propagation for 1:1 threading's POSIX priority mutexes, the code is no-op unless priority-aware umtx code is committed.
2006-08-25 06:12:53 +00:00
#include <sys/umtx.h>
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
#include <sys/vmmeter.h>
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
#include <sys/cpuset.h>
Introduce a new sysctl, kern.sched.topology_spec, that returns an XML dump of detected ULE CPU topology. This dump can be used to check the topology detection and for general system information. An example of CPU topology dump is: kern.sched.topology_spec: <groups> <group level="1" cache-level="0"> <cpu count="8" mask="0xff">0, 1, 2, 3, 4, 5, 6, 7</cpu> <flags></flags> <children> <group level="2" cache-level="0"> <cpu count="4" mask="0xf">0, 1, 2, 3</cpu> <flags></flags> </group> <group level="2" cache-level="0"> <cpu count="4" mask="0xf0">4, 5, 6, 7</cpu> <flags></flags> </group> </children> </group> </groups> Reviewed by: jeff Approved by: gnn (mentor)
2008-10-29 13:36:23 +00:00
#include <sys/sbuf.h>
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
Bring a working snapshot of hwpmc(4), its associated libraries, userland utilities and documentation into -CURRENT. Bump FreeBSD_version. Reviewed by: alc, jhb (kernel changes)
2005-04-19 04:01:25 +00:00
#ifdef HWPMC_HOOKS
#include <sys/pmckern.h>
#endif
Add the vtime (virtual time) hooks for DTrace.
2008-05-25 01:44:58 +00:00
#ifdef KDTRACE_HOOKS
#include <sys/dtrace_bsd.h>
int dtrace_vtime_active;
dtrace_vtime_switch_func_t dtrace_vtime_switch_func;
#endif
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
#include <machine/cpu.h>
- Add static to local functions and data where it was missing. - Add an IPI based mechanism for migrating kses. This mechanism is broken down into several components. This is intended to reduce cache thrashing by eliminating most cases where one cpu touches another's run queues. - kseq_notify() appends a kse to a lockless singly linked list and conditionally sends an IPI to the target processor. Right now this is protected by sched_lock but at some point I'd like to get rid of the global lock. This is why I used something more complicated than a standard queue. - kseq_assign() processes our list of kses that have been assigned to us by other processors. This simply calls sched_add() for each item on the list after clearing the new KEF_ASSIGNED flag. This flag is used to indicate that we have been appeneded to the assigned queue but not added to the run queue yet. - In sched_add(), instead of adding a KSE to another processor's queue we use kse_notify() so that we don't touch their queue. Also in sched_add(), if KEF_ASSIGNED is already set return immediately. This can happen if a thread is removed and readded so that the priority is recorded properly. - In sched_rem() return immediately if KEF_ASSIGNED is set. All callers immediately readd simply to adjust priorites etc. - In sched_choose(), if we're running an IDLE task or the per cpu idle thread set our cpumask bit in 'kseq_idle' so that other processors may know that we are idle. Before this, make a single pass through the run queues of other processors so that we may find work more immediately if it is available. - In sched_runnable(), don't scan each processor's run queue, they will IPI us if they have work for us to do. - In sched_add(), if we're adding a thread that can be migrated and we have plenty of work to do, try to migrate the thread to an idle kseq. - Simplify the logic in sched_prio() and take the KEF_ASSIGNED flag into consideration. - No longer use kseq_choose() to steal threads, it can lose it's last argument. - Create a new function runq_steal() which operates like runq_choose() but skips threads based on some criteria. Currently it will not steal PRI_ITHD threads. In the future this will be used for CPU binding. - Create a kseq_steal() that checks each run queue with runq_steal(), use kseq_steal() in the places where we used kseq_choose() to steal with before.
2003-10-31 11:16:04 +00:00
#include <machine/smp.h>
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
#define KTR_ULE 0
- Get rid of the unused DIDRUN flag. This was really only present to support sched_4bsd. - Rename the KTR level for non schedgraph parsed events. They take event space from things we'd like to graph. - Reset our slice value after we sleep. The slice is simply there to prevent starvation among equal priorities. A thread which had almost exhausted it's slice and then slept doesn't need to be rescheduled a tick after it wakes up. - Set the maximum slice value to a more conservative 100ms now that it is more accurately enforced.
2007-01-25 19:14:11 +00:00
- Use __XSTRING where I want the define to be expanded. This resulted in sizeof("MAXCPU") being used to calculate a string length rather than something more reasonable such as sizeof("32"). This shouldn't have caused any ill effect until we run on machines with 1000000 or more cpus.
2009-01-25 07:35:10 +00:00
#define TS_NAME_LEN (MAXCOMLEN + sizeof(" td ") + sizeof(__XSTRING(UINT_MAX)))
#define TDQ_NAME_LEN (sizeof("sched lock ") + sizeof(__XSTRING(MAXCPU)))
Remove explicit MAXCPU usage from sys/pcpu.h avoiding a namespace pollution. That is a step further in the direction of building correct policies for userland and modules on how to deal with the number of maxcpus at runtime. Reported by: jhb Reviewed and tested by: pluknet Approved by: re (kib)
2011-07-19 16:50:55 +00:00
#define TDQ_LOADNAME_LEN (sizeof("CPU ") + sizeof(__XSTRING(MAXCPU)) - 1 + sizeof(" load"))
- Implement generic macros for producing KTR records that are compatible with src/tools/sched/schedgraph.py. This allows developers to quickly create a graphical view of ktr data for any resource in the system. - Add sched_tdname() and the pcpu field 'name' for quickly and uniformly identifying records associated with a thread or cpu. - Reimplement the KTR_SCHED traces using the new generic facility. Obtained from: attilio Discussed with: jhb Sponsored by: Nokia
2009-01-17 07:17:57 +00:00
- Don't SLOT_USE() in the preempt case, sched_add() has already taken the slot for us. Previously, we would take two slots on every preempt, and setrunqueue() would fix it up for us in the non threaded case. The threaded case was simply broken. - Clean up flags, prototypes, comments.
2005-06-04 09:23:28 +00:00
/*
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
* Thread scheduler specific section. All fields are protected
* by the thread lock.
Refactor a bunch of scheduler code to give basically the same behaviour but with slightly cleaned up interfaces. The KSE structure has become the same as the "per thread scheduler private data" structure. In order to not make the diffs too great one is #defined as the other at this time. The KSE (or td_sched) structure is now allocated per thread and has no allocation code of its own. Concurrency for a KSEGRP is now kept track of via a simple pair of counters rather than using KSE structures as tokens. Since the KSE structure is different in each scheduler, kern_switch.c is now included at the end of each scheduler. Nothing outside the scheduler knows the contents of the KSE (aka td_sched) structure. The fields in the ksegrp structure that are to do with the scheduler's queueing mechanisms are now moved to the kg_sched structure. (per ksegrp scheduler private data structure). In other words how the scheduler queues and keeps track of threads is no-one's business except the scheduler's. This should allow people to write experimental schedulers with completely different internal structuring. A scheduler call sched_set_concurrency(kg, N) has been added that notifies teh scheduler that no more than N threads from that ksegrp should be allowed to be on concurrently scheduled. This is also used to enforce 'fainess' at this time so that a ksegrp with 10000 threads can not swamp a the run queue and force out a process with 1 thread, since the current code will not set the concurrency above NCPU, and both schedulers will not allow more than that many onto the system run queue at a time. Each scheduler should eventualy develop their own methods to do this now that they are effectively separated. Rejig libthr's kernel interface to follow the same code paths as linkse for scope system threads. This has slightly hurt libthr's performance but I will work to recover as much of it as I can. Thread exit code has been cleaned up greatly. exit and exec code now transitions a process back to 'standard non-threaded mode' before taking the next step. Reviewed by: scottl, peter MFC after: 1 week
2004-09-05 02:09:54 +00:00
*/
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
struct td_sched {
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
struct runq *ts_runq; /* Run-queue we're queued on. */
short ts_flags; /* TSF_* flags. */
Update the ULE scheduler + thread and kinfo structs to use int for cpuid rather than u_char. To try and play nice with the ABI, the u_char CPU ID values are clamped at 254. The new fields now contain the full CPU ID, or -1 for no cpu. Differential Revision: D955 Reviewed by: jhb, kib Sponsored by: Norse Corp, Inc.
2014-10-18 19:36:11 +00:00
int ts_cpu; /* CPU that we have affinity for. */
Reduce ULE context switch time by over 25%. - Only calculate timeshare priorities once per tick or when a thread is woken from sleeping. - Keep the ts_runq pointer valid after all priority changes. - Call tdq_runq_add() directly from sched_switch() without passing in via tdq_add(). We don't need to adjust loads or runqs anymore. - Sort tdq and ts_sched according to utilization to improve cache behavior. Sponsored by: Nokia
2008-03-10 03:15:19 +00:00
int ts_rltick; /* Real last tick, for affinity. */
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
int ts_slice; /* Ticks of slice remaining. */
u_int ts_slptime; /* Number of ticks we vol. slept */
u_int ts_runtime; /* Number of ticks we were running */
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
int ts_ltick; /* Last tick that we were running on */
int ts_ftick; /* First tick that we were running on */
int ts_ticks; /* Tick count */
- Implement generic macros for producing KTR records that are compatible with src/tools/sched/schedgraph.py. This allows developers to quickly create a graphical view of ktr data for any resource in the system. - Add sched_tdname() and the pcpu field 'name' for quickly and uniformly identifying records associated with a thread or cpu. - Reimplement the KTR_SCHED traces using the new generic facility. Obtained from: attilio Discussed with: jhb Sponsored by: Nokia
2009-01-17 07:17:57 +00:00
#ifdef KTR
char ts_name[TS_NAME_LEN];
#endif
Refactor a bunch of scheduler code to give basically the same behaviour but with slightly cleaned up interfaces. The KSE structure has become the same as the "per thread scheduler private data" structure. In order to not make the diffs too great one is #defined as the other at this time. The KSE (or td_sched) structure is now allocated per thread and has no allocation code of its own. Concurrency for a KSEGRP is now kept track of via a simple pair of counters rather than using KSE structures as tokens. Since the KSE structure is different in each scheduler, kern_switch.c is now included at the end of each scheduler. Nothing outside the scheduler knows the contents of the KSE (aka td_sched) structure. The fields in the ksegrp structure that are to do with the scheduler's queueing mechanisms are now moved to the kg_sched structure. (per ksegrp scheduler private data structure). In other words how the scheduler queues and keeps track of threads is no-one's business except the scheduler's. This should allow people to write experimental schedulers with completely different internal structuring. A scheduler call sched_set_concurrency(kg, N) has been added that notifies teh scheduler that no more than N threads from that ksegrp should be allowed to be on concurrently scheduled. This is also used to enforce 'fainess' at this time so that a ksegrp with 10000 threads can not swamp a the run queue and force out a process with 1 thread, since the current code will not set the concurrency above NCPU, and both schedulers will not allow more than that many onto the system run queue at a time. Each scheduler should eventualy develop their own methods to do this now that they are effectively separated. Rejig libthr's kernel interface to follow the same code paths as linkse for scope system threads. This has slightly hurt libthr's performance but I will work to recover as much of it as I can. Thread exit code has been cleaned up greatly. exit and exec code now transitions a process back to 'standard non-threaded mode' before taking the next step. Reviewed by: scottl, peter MFC after: 1 week
2004-09-05 02:09:54 +00:00
};
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
/* flags kept in ts_flags */
Major revamp of ULE's cpu load balancing: - Switch back to direct modification of remote CPU run queues. This added a lot of complexity with questionable gain. It's easy enough to reimplement if it's shown to help on huge machines. - Re-implement the old tdq_transfer() call as tdq_pickidle(). Change sched_add() so we have selectable cpu choosers and simplify the logic a bit here. - Implement tdq_pickpri() as the new default cpu chooser. This algorithm is similar to Solaris in that it tries to always run the threads with the best priorities. It is actually slightly more complex than solaris's algorithm because we also tend to favor the local cpu over other cpus which has a boost in latency but also potentially enables cache sharing between the waking thread and the woken thread. - Add a bunch of tunables that can be used to measure effects of different load balancing strategies. Most of these will go away once the algorithm is more definite. - Add a new mechanism to steal threads from busy cpus when we idle. This is enabled with kern.sched.steal_busy and kern.sched.busy_thresh. The threshold is the required length of a tdq's run queue before another cpu will be able to steal runnable threads. This prevents most queue imbalances that contribute the long latencies.
2007-01-19 21:56:08 +00:00
#define TSF_BOUND 0x0001 /* Thread can not migrate. */
#define TSF_XFERABLE 0x0002 /* Thread was added as transferable. */
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
#define THREAD_CAN_MIGRATE(td) ((td)->td_pinned == 0)
#define THREAD_CAN_SCHED(td, cpu) \
CPU_ISSET((cpu), &(td)->td_cpuset->cs_mask)
Get rid of struct proc p_sched and struct thread td_sched pointers. p_sched is unused. The struct td_sched is always co-allocated with the struct thread, except for the thread0. Avoid useless indirection, instead calculate td_sched location using simple pointer arithmetic in td_get_sched(9). For thread0, which is statically allocated, create a structure to emulate layout of the dynamic allocation. Reviewed by: jhb (previous version) Sponsored by: The FreeBSD Foundation Differential revision: https://reviews.freebsd.org/D6711
2016-06-05 17:04:03 +00:00
_Static_assert(sizeof(struct thread) + sizeof(struct td_sched) <=
sizeof(struct thread0_storage),
"increase struct thread0_storage.t0st_sched size");
Introduce two new helper macros to define the priority ranges used for interactive timeshare threads (PRI_*_INTERACTIVE) and non-interactive timeshare threads (PRI_*_BATCH) and use these instead of PRI_*_REALTIME and PRI_*_TIMESHARE. No functional change. Reviewed by: jeff
2011-01-13 14:22:27 +00:00
/*
* Priority ranges used for interactive and non-interactive timeshare
Rework realtime priority support: - Move the realtime priority range up above kernel sleep priorities and just below interrupt thread priorities. - Contract the interrupt and kernel sleep priority ranges a bit so that the timesharing priority band can be increased. The new timeshare range is now slightly larger than the old realtime + timeshare ranges. - Change the ULE scheduler to no longer use realtime priorities for interactive threads. Instead, the larger timeshare range is now split into separate subranges for interactive and non-interactive ("batch") threads. The end result is that interactive threads and non-interactive threads still use the same priority ranges as before, but realtime threads now have a separate, dedicated priority range. - Do not modify the priority of non-timeshare threads in sched_sleep() or via cv_broadcastpri(). Realtime and idle priority threads will no longer have their priorities affected by sleeping in the kernel. Reviewed by: jeff
2011-01-14 17:06:54 +00:00
* threads. The timeshare priorities are split up into four ranges.
* The first range handles interactive threads. The last three ranges
* (NHALF, x, and NHALF) handle non-interactive threads with the outer
* ranges supporting nice values.
Introduce two new helper macros to define the priority ranges used for interactive timeshare threads (PRI_*_INTERACTIVE) and non-interactive timeshare threads (PRI_*_BATCH) and use these instead of PRI_*_REALTIME and PRI_*_TIMESHARE. No functional change. Reviewed by: jeff
2011-01-13 14:22:27 +00:00
*/
Rework realtime priority support: - Move the realtime priority range up above kernel sleep priorities and just below interrupt thread priorities. - Contract the interrupt and kernel sleep priority ranges a bit so that the timesharing priority band can be increased. The new timeshare range is now slightly larger than the old realtime + timeshare ranges. - Change the ULE scheduler to no longer use realtime priorities for interactive threads. Instead, the larger timeshare range is now split into separate subranges for interactive and non-interactive ("batch") threads. The end result is that interactive threads and non-interactive threads still use the same priority ranges as before, but realtime threads now have a separate, dedicated priority range. - Do not modify the priority of non-timeshare threads in sched_sleep() or via cv_broadcastpri(). Realtime and idle priority threads will no longer have their priorities affected by sleeping in the kernel. Reviewed by: jeff
2011-01-14 17:06:54 +00:00
#define PRI_TIMESHARE_RANGE (PRI_MAX_TIMESHARE - PRI_MIN_TIMESHARE + 1)
#define PRI_INTERACT_RANGE ((PRI_TIMESHARE_RANGE - SCHED_PRI_NRESV) / 2)
ule: ensure that batch timeshare threads are scheduled fairly With the previous code, if the range of priorities for timeshare batch threads was greater than RQ_NQS, then the threads with low priorities in the part of the range above RQ_NQS would be scheduled to the run-queues as if they had high priorities at the beginning of the range. In other words, threads with a nice level of +N could be scheduled as if they had a nice level of -M. Reported by: George Mitchell <george@m5p.com> Reviewed by: jhb Tested by: George Mitchell <george@m5p.com> (earlier version) MFC after: 1 week
2011-12-19 20:01:21 +00:00
#define PRI_BATCH_RANGE (PRI_TIMESHARE_RANGE - PRI_INTERACT_RANGE)
Rework realtime priority support: - Move the realtime priority range up above kernel sleep priorities and just below interrupt thread priorities. - Contract the interrupt and kernel sleep priority ranges a bit so that the timesharing priority band can be increased. The new timeshare range is now slightly larger than the old realtime + timeshare ranges. - Change the ULE scheduler to no longer use realtime priorities for interactive threads. Instead, the larger timeshare range is now split into separate subranges for interactive and non-interactive ("batch") threads. The end result is that interactive threads and non-interactive threads still use the same priority ranges as before, but realtime threads now have a separate, dedicated priority range. - Do not modify the priority of non-timeshare threads in sched_sleep() or via cv_broadcastpri(). Realtime and idle priority threads will no longer have their priorities affected by sleeping in the kernel. Reviewed by: jeff
2011-01-14 17:06:54 +00:00
#define PRI_MIN_INTERACT PRI_MIN_TIMESHARE
#define PRI_MAX_INTERACT (PRI_MIN_TIMESHARE + PRI_INTERACT_RANGE - 1)
#define PRI_MIN_BATCH (PRI_MIN_TIMESHARE + PRI_INTERACT_RANGE)
Introduce two new helper macros to define the priority ranges used for interactive timeshare threads (PRI_*_INTERACTIVE) and non-interactive timeshare threads (PRI_*_BATCH) and use these instead of PRI_*_REALTIME and PRI_*_TIMESHARE. No functional change. Reviewed by: jeff
2011-01-13 14:22:27 +00:00
#define PRI_MAX_BATCH PRI_MAX_TIMESHARE
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
/*
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
* Cpu percentage computation macros and defines.
*
* SCHED_TICK_SECS: Number of seconds to average the cpu usage across.
* SCHED_TICK_TARG: Number of hz ticks to average the cpu usage across.
- ftick was initialized to -1 for init and any of it's children. Fix this by setting ftick = ltick = ticks in schedinit(). - Update the priority when we are pulled off of the run queue and when we are inserted onto the run queue so that it more accurately reflects our present status. This is important for efficient priority propagation functioning. - Move the frequency test into sched_pctcpu_update() so we don't repeat it each time we'd like to call it. - Put some temporary work-around code in sched_priority() in case the tick mechanism produces a bad priority. Eventually this should revert to an assert again.
2007-01-05 08:50:38 +00:00
* SCHED_TICK_MAX: Maximum number of ticks before scaling back.
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
* SCHED_TICK_SHIFT: Shift factor to avoid rounding away results.
* SCHED_TICK_HZ: Compute the number of hz ticks for a given ticks count.
* SCHED_TICK_TOTAL: Gives the amount of time we've been recording ticks.
*/
#define SCHED_TICK_SECS 10
#define SCHED_TICK_TARG (hz * SCHED_TICK_SECS)
- ftick was initialized to -1 for init and any of it's children. Fix this by setting ftick = ltick = ticks in schedinit(). - Update the priority when we are pulled off of the run queue and when we are inserted onto the run queue so that it more accurately reflects our present status. This is important for efficient priority propagation functioning. - Move the frequency test into sched_pctcpu_update() so we don't repeat it each time we'd like to call it. - Put some temporary work-around code in sched_priority() in case the tick mechanism produces a bad priority. Eventually this should revert to an assert again.
2007-01-05 08:50:38 +00:00
#define SCHED_TICK_MAX (SCHED_TICK_TARG + hz)
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
#define SCHED_TICK_SHIFT 10
#define SCHED_TICK_HZ(ts) ((ts)->ts_ticks >> SCHED_TICK_SHIFT)
- Don't let SCHED_TICK_TOTAL() return less than hz. This can cause integer divide faults in roundup() later if it is able to return 0. For some reason this bug only shows up on my laptop and not my testboxes.
2007-01-06 12:33:43 +00:00
#define SCHED_TICK_TOTAL(ts) (max((ts)->ts_ltick - (ts)->ts_ftick, hz))
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
/*
* These macros determine priorities for non-interactive threads. They are
* assigned a priority based on their recent cpu utilization as expressed
* by the ratio of ticks to the tick total. NHALF priorities at the start
* and end of the MIN to MAX timeshare range are only reachable with negative
* or positive nice respectively.
- Create a function sched_interact_score() which decides on the interactivity of a kseg and assigns it a value of 0 through 100. - Use sched_interact_score() to determine the dynamic priority. - Define SCHED_CURR() in terms of sched_interact_score(). - Adjust the maximum slice back down to 100ms. - Remove redundant clearing of ke_runq in sched_wakeup() - Clean up #defines and comment them.
2003-03-04 02:45:59 +00:00
*
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
* PRI_RANGE: Priority range for utilization dependent priorities.
- Don't allow nice to have such a large effect on priority. This was causing poor interactive performance while unnice processes were running. The new scheme still allows nice to have an effect on priority but it is not as dramatic as the effect of the interactivity score.
2003-06-21 02:22:47 +00:00
* PRI_NRESV: Number of nice values.
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
* PRI_TICKS: Compute a priority in PRI_RANGE from the ticks count and total.
* PRI_NICE: Determines the part of the priority inherited from nice.
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
*/
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
#define SCHED_PRI_NRESV (PRIO_MAX - PRIO_MIN)
- Remove uses of PRIO_TOTAL and replace them with SCHED_PRI_NRESV - SCHED_PRI_NRESV does not have the off by one error in PRIO_TOTAL so we do not have to account for it in the few places that we use it. Requested by: bde
2003-11-02 03:49:32 +00:00
#define SCHED_PRI_NHALF (SCHED_PRI_NRESV / 2)
Introduce two new helper macros to define the priority ranges used for interactive timeshare threads (PRI_*_INTERACTIVE) and non-interactive timeshare threads (PRI_*_BATCH) and use these instead of PRI_*_REALTIME and PRI_*_TIMESHARE. No functional change. Reviewed by: jeff
2011-01-13 14:22:27 +00:00
#define SCHED_PRI_MIN (PRI_MIN_BATCH + SCHED_PRI_NHALF)
#define SCHED_PRI_MAX (PRI_MAX_BATCH - SCHED_PRI_NHALF)
Fix two harmless off-by-one errors. Reviewed by: jeff MFC after: 2 weeks
2011-01-10 20:48:10 +00:00
#define SCHED_PRI_RANGE (SCHED_PRI_MAX - SCHED_PRI_MIN + 1)
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
#define SCHED_PRI_TICKS(ts) \
(SCHED_TICK_HZ((ts)) / \
- Fix the sched_priority() invalid priority bugs. Use roundup() instead of max() when computing the divisor in SCHED_TICK_PRI(). This prevents cases where rounding down would allow the quotient to exceed SCHED_PRI_RANGE. - Garbage collect some unused flags and fields. - Replace TDF_HOLD with sched_pin_td()/sched_unpin_td() since it simply duplicated this functionality. - Re-enable the rebalancer by default and fix the sysctl so it can be modified.
2007-01-06 08:44:13 +00:00
(roundup(SCHED_TICK_TOTAL((ts)), SCHED_PRI_RANGE) / SCHED_PRI_RANGE))
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
#define SCHED_PRI_NICE(nice) (nice)
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
/*
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
* These determine the interactivity of a process. Interactivity differs from
* cpu utilization in that it expresses the voluntary time slept vs time ran
* while cpu utilization includes all time not running. This more accurately
* models the intent of the thread.
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
*
- Add a new variable 'kg_runtime' that tracks the amount of time we've run. - Use the ratio of kg_runtime / kg_slptime to determine our dynamic priority. - Scale kg_runtime and kg_slptime back when the sum of the two exceeds SCHED_SLP_RUN_MAX. This allows us to slowly forget old behavior. - Scale back the runtime and slptime in fork so that the new process has the same ratio but much less accumulated time. This causes new behavior to be noticed more quickly.
2003-02-10 14:03:45 +00:00
* SLP_RUN_MAX: Maximum amount of sleep time + run time we'll accumulate
* before throttling back.
- Change sched_interact_update() to only accept slp+runtime values between 0 and SCHED_SLP_RUN_MAX * 2. This allows us to simplify the algorithm quite a bit. Before, it dealt with arbitrary values which required us to do nasty integer division tricks that didn't quite work out correctly. - Chnage sched_wakeup() to detect conditions where the slp+runtime could exceed SCHED_SLP_RUN_MAX * 2. This can happen if we go to sleep for longer than 6 seconds. In this case, we'll just clear the runtime and set the sleep time to the max. - Define a new function, sched_interact_fork() which updates the slp+runtime of a newly forked thread. We want to limit the amount of history retained from the parent so that we learn the child's behavior quickly. We don't, however want to decay it to nothing. Previously, we would simply divide each parameter by 100 whenever we forked. After a few forks the values would reach 0 and tasks would not be considered interactive. - Add another KTR entry, cleanup some existing entries. - Remove a useless sched_interact_update() from sched_priority(). This is already done by the callers that require it.
2003-11-02 03:36:33 +00:00
* SLP_RUN_FORK: Maximum slp+run time to inherit at fork time.
- Fix the maximum slice value. I accidentally checked in a value of '2' which meant no process would run for longer than 20ms. - Slightly redo the interactivity scorer. It follows the same algorithm but in a slightly more correct way. Previously values above half were incorrect. - Lower the interactivity threshold to 20. It seems that in testing non- interactive tasks are hardly ever near there and expensive interactive tasks can sometimes surpass it. This area needs more testing. - Remove an unnecessary KTR. - Fix a case where an idle thread that had an elevated priority due to priority prop. would be placed back on the idle queue. - Delay setting NEEDRESCHED until userret() for threads that haad their priority elevated while in kernel. This gives us the same context switch optimization as SCHED_4BSD. - Limit the child's slice to 1 in sched_fork_kse() so we detect its behavior more quickly. - Inhert some of the run/slp time from the child in sched_exit_ksegrp(). - Redo some of the priority comparisons so they are more clear. - Throttle the frequency of sched_pctcpu_update() so that rounding errors do not make it invalid.
2003-06-15 02:18:29 +00:00
* INTERACT_MAX: Maximum interactivity value. Smaller is better.
Fix typos. Submitted by: gianni MFC after: 3 days
2010-11-10 21:06:49 +00:00
* INTERACT_THRESH: Threshold for placement on the current runq.
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
*/
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
#define SCHED_SLP_RUN_MAX ((hz * 5) << SCHED_TICK_SHIFT)
#define SCHED_SLP_RUN_FORK ((hz / 2) << SCHED_TICK_SHIFT)
- Fix the maximum slice value. I accidentally checked in a value of '2' which meant no process would run for longer than 20ms. - Slightly redo the interactivity scorer. It follows the same algorithm but in a slightly more correct way. Previously values above half were incorrect. - Lower the interactivity threshold to 20. It seems that in testing non- interactive tasks are hardly ever near there and expensive interactive tasks can sometimes surpass it. This area needs more testing. - Remove an unnecessary KTR. - Fix a case where an idle thread that had an elevated priority due to priority prop. would be placed back on the idle queue. - Delay setting NEEDRESCHED until userret() for threads that haad their priority elevated while in kernel. This gives us the same context switch optimization as SCHED_4BSD. - Limit the child's slice to 1 in sched_fork_kse() so we detect its behavior more quickly. - Inhert some of the run/slp time from the child in sched_exit_ksegrp(). - Redo some of the priority comparisons so they are more clear. - Throttle the frequency of sched_pctcpu_update() so that rounding errors do not make it invalid.
2003-06-15 02:18:29 +00:00
#define SCHED_INTERACT_MAX (100)
#define SCHED_INTERACT_HALF (SCHED_INTERACT_MAX / 2)
- The non iterative algorithm for interact_update was broken due to rounding errors. This was the source of the majority of the interactivity problems. Reintroduce the old algorithm and its XXX. - Up the interactivity threshold to 30. It really could stand to be even a tiny bit higher. - Let the sleep and run time accumulate up to 5 seconds of history rather than two. This helps stop XFree86 from becoming non-interactive during bursts of activity.
2003-10-16 08:17:43 +00:00
#define SCHED_INTERACT_THRESH (30)
- Create a function sched_interact_score() which decides on the interactivity of a kseg and assigns it a value of 0 through 100. - Use sched_interact_score() to determine the dynamic priority. - Define SCHED_CURR() in terms of sched_interact_score(). - Adjust the maximum slice back down to 100ms. - Remove redundant clearing of ke_runq in sched_wakeup() - Clean up #defines and comment them.
2003-03-04 02:45:59 +00:00
- Change ULE to use dynamic slice sizes for the timeshare queue in order to further reduce latency for threads in this queue. This should help as threads transition from realtime to timeshare. The latency is bound to a max of sched_slice until we have more than sched_slice / 6 threads runnable. Then the min slice is allotted to all threads and latency becomes (nthreads - 1) * min_slice. Discussed with: mav
2012-11-08 01:46:47 +00:00
/*
* These parameters determine the slice behavior for batch work.
*/
#define SCHED_SLICE_DEFAULT_DIVISOR 10 /* ~94 ms, 12 stathz ticks. */
#define SCHED_SLICE_MIN_DIVISOR 6 /* DEFAULT/MIN = ~16 ms. */
Rework r220198 change (by fabient). I believe it solves the problem from the wrong direction. Before it, if preemption and end of time slice happen same time, thread was put to the head of the queue as for only preemption. It could cause single thread to run for indefinitely long time. r220198 handles it by not clearing TDF_NEEDRESCHED in case of preemption. But that causes delayed context switch every time preemption happens, even when not needed. Solve problem by introducing scheduler-specifoc thread flag TDF_SLICEEND, set when thread's time slice is over and it should be put to the tail of queue. Using SW_PREEMPT flag for that purpose as it was before just not enough informative to work correctly. On my tests this by 2-3 times reduces run time deviation (improves fairness) in cases when several threads share one CPU. Reviewed by: fabient MFC after: 2 months Sponsored by: iXsystems, Inc.
2012-08-09 19:26:13 +00:00
/* Flags kept in td_flags. */
#define TDF_SLICEEND TDF_SCHED2 /* Thread time slice is over. */
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
/*
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
* tickincr: Converts a stathz tick into a hz domain scaled by
* the shift factor. Without the shift the error rate
* due to rounding would be unacceptably high.
* realstathz: stathz is sometimes 0 and run off of hz.
* sched_slice: Runtime of each thread before rescheduling.
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
* preempt_thresh: Priority threshold for preemption and remote IPIs.
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
*/
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
static int sched_interact = SCHED_INTERACT_THRESH;
remove duplicate semicolons where possible. Approved by: cperciva MFC after: 1 week
2012-10-22 03:00:37 +00:00
static int tickincr = 8 << SCHED_TICK_SHIFT;
- Change ULE to use dynamic slice sizes for the timeshare queue in order to further reduce latency for threads in this queue. This should help as threads transition from realtime to timeshare. The latency is bound to a max of sched_slice until we have more than sched_slice / 6 threads runnable. Then the min slice is allotted to all threads and latency becomes (nthreads - 1) * min_slice. Discussed with: mav
2012-11-08 01:46:47 +00:00
static int realstathz = 127; /* reset during boot. */
static int sched_slice = 10; /* reset during boot. */
static int sched_slice_min = 1; /* reset during boot. */
- Honor the PREEMPTION and FULL_PREEMPTION flags by setting the default value for kern.sched.preempt_thresh appropriately. It can still by adjusted at runtime. ULE will still use IPI_PREEMPT in certain migration situations. - Assert that we're not trying to compile ULE on an unsupported architecture. To date, I believe only i386 and amd64 have implemented the third cpu switch argument required. Approved by: re
2007-09-27 16:39:27 +00:00
#ifdef PREEMPTION
#ifdef FULL_PREEMPTION
static int preempt_thresh = PRI_MAX_IDLE;
#else
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
static int preempt_thresh = PRI_MIN_KERN;
- Honor the PREEMPTION and FULL_PREEMPTION flags by setting the default value for kern.sched.preempt_thresh appropriately. It can still by adjusted at runtime. ULE will still use IPI_PREEMPT in certain migration situations. - Assert that we're not trying to compile ULE on an unsupported architecture. To date, I believe only i386 and amd64 have implemented the third cpu switch argument required. Approved by: re
2007-09-27 16:39:27 +00:00
#endif
#else
static int preempt_thresh = 0;
#endif
Introduce two new helper macros to define the priority ranges used for interactive timeshare threads (PRI_*_INTERACTIVE) and non-interactive timeshare threads (PRI_*_BATCH) and use these instead of PRI_*_REALTIME and PRI_*_TIMESHARE. No functional change. Reviewed by: jeff
2011-01-13 14:22:27 +00:00
static int static_boost = PRI_MIN_BATCH;
- Add a metric to describe how busy a processor has been over the last two ticks by counting the number of switches and the load when sched_clock() is called. - If the busy metric exceeds a threshold allow the idle thread to spin waiting for new work for a brief period to avoid using IPIs. This reduces the cost on the sender and receiver as well as reducing wakeup latency considerably when it works. Sponsored by: Nokia
2008-04-17 09:56:01 +00:00
static int sched_idlespins = 10000;
Make kern.sched.idlespinthresh default value adaptive depending of HZ. Otherwise with HZ above 8000 CPU may never skip timer ticks on idle.
2012-03-09 19:09:08 +00:00
static int sched_idlespinthresh = -1;
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
/*
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
* tdq - per processor runqs and statistics. All fields are protected by the
* tdq_lock. The load and lowpri may be accessed without to avoid excess
* locking in sched_pickcpu();
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
*/
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
struct tdq {
Pad tdq_lock to avoid false sharing with tdq_load and tdq_cpu_idle. This enables CPU searches (which read tdq_load) to operate independently of any contention on the spinlock. Some scheduler-intensive workloads running on an 8C single-socket SNB Xeon show considerable improvement with this change (2-3% perf improvement, 5-6% decrease in CPU util). Sponsored by: Intel Reviewed by: jeff
2012-10-24 18:36:41 +00:00
/*
* Ordered to improve efficiency of cpu_search() and switch().
* tdq_lock is padded to avoid false sharing with tdq_load and
* tdq_cpu_idle.
*/
Rework the known mutexes to benefit about staying on their own cache line in order to avoid manual frobbing but using struct mtx_padalign. The sole exception being nvme and sxfge drivers, where the author redefined CACHE_LINE_SIZE manually, so they need to be analyzed and dealt with separately. Reviwed by: jimharris, alc
2012-10-31 18:07:18 +00:00
struct mtx_padalign tdq_lock; /* run queue lock. */
Reduce ULE context switch time by over 25%. - Only calculate timeshare priorities once per tick or when a thread is woken from sleeping. - Keep the ts_runq pointer valid after all priority changes. - Call tdq_runq_add() directly from sched_switch() without passing in via tdq_add(). We don't need to adjust loads or runqs anymore. - Sort tdq and ts_sched according to utilization to improve cache behavior. Sponsored by: Nokia
2008-03-10 03:15:19 +00:00
struct cpu_group *tdq_cg; /* Pointer to cpu topology. */
- Add a metric to describe how busy a processor has been over the last two ticks by counting the number of switches and the load when sched_clock() is called. - If the busy metric exceeds a threshold allow the idle thread to spin waiting for new work for a brief period to avoid using IPIs. This reduces the cost on the sender and receiver as well as reducing wakeup latency considerably when it works. Sponsored by: Nokia
2008-04-17 09:56:01 +00:00
volatile int tdq_load; /* Aggregate load. */
Do not IPI CPU that is already spinning for load. It doubles effect of spining (comparing to MWAIT) on some heavly switching test loads.
2010-09-10 13:24:47 +00:00
volatile int tdq_cpu_idle; /* cpu_idle() is active. */
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
int tdq_sysload; /* For loadavg, !ITHD load. */
Decrease latency by not wrapping the idle loop's potentially lengthy search for a thread to steal inside a critical section. Since this allows the search to be preempted, restart the search if preemption happens since the search results found earlier may no longer be valid. Decrease the latency of starting a thread that may be assigned to this CPU during the search by polling for incoming threads during the search and switching to that thread instead of continuing the search. Test for stale search results and restart the search before going through the expense of calling tdq_lock_pair(). Retry some tests after grabbing the locks since things may have changed while waiting to get both locks. Eliminate special case handling for stealing from an SMT peer that uses 1 as the steal threshold. This can only succeed if a thread has been assigned but our SMT peer has not yet started executing it. This is quite rare and when it happens the other SMT thread is generally waiting for the same tdq lock that we hold. Basically both SMT threads are racing to grab the same spin lock. Add the kern.sched.always_steal knob from a ULE patch by jeff@. Incorporate another idea from Jeff's ULE patch. If the sched_switch() detects that the CPU is about to go idle, try to steal a thread before switching to the idle thread. Since the search for a thread to steal has to be done inside a critical section in this context, limit the impact on latency by adding the knob kern.sched.trysteal_limit to limit the topological distance of the search and don't restart the search if we detect stale results. If this search can't find an stealable thread, the idle loop can do a more complete search. Also poll for threads being assigned to this CPU during the search and switch to them instead of continuing the search. This change is responsibile for the majority of the improvement in parallel buildworld times. In sched_balance_group() change the minimum threshold from stealing a thread from 1 to 2. Poaching a newly assigned thread from a CPU that is waking up hasn't yet switched to that thread from idle is likely very rare and is likely to have the same lock race as is seen when stealing threads in the idle loop. Also use tdq_notify() to kick the destintation CPU instead of always sending an IPI. Update a stale comment, the number of transferable threads is not calculated. Reviewed by: kib (earlier version) Comments by: avg, jeff, mav MFC after: 1 month Differential Revision: https://reviews.freebsd.org/D12130
2018-02-23 00:12:51 +00:00
volatile int tdq_transferable; /* Transferable thread count. */
volatile short tdq_switchcnt; /* Switches this tick. */
volatile short tdq_oldswitchcnt; /* Switches last tick. */
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
u_char tdq_lowpri; /* Lowest priority thread. */
- Add an implementation of sched_preempt() that avoids excessive IPIs. - Normalize the preemption/ipi setting code by introducing sched_shouldpreempt() so the logical is identical and not repeated between tdq_notify() and sched_setpreempt(). - In tdq_notify() don't set NEEDRESCHED as we may not actually own the thread lock this could have caused us to lose td_flags settings. - Garbage collect some tunables that are no longer relevant.
2008-03-10 01:32:01 +00:00
u_char tdq_ipipending; /* IPI pending. */
Reduce ULE context switch time by over 25%. - Only calculate timeshare priorities once per tick or when a thread is woken from sleeping. - Keep the ts_runq pointer valid after all priority changes. - Call tdq_runq_add() directly from sched_switch() without passing in via tdq_add(). We don't need to adjust loads or runqs anymore. - Sort tdq and ts_sched according to utilization to improve cache behavior. Sponsored by: Nokia
2008-03-10 03:15:19 +00:00
u_char tdq_idx; /* Current insert index. */
u_char tdq_ridx; /* Current removal index. */
struct runq tdq_realtime; /* real-time run queue. */
struct runq tdq_timeshare; /* timeshare run queue. */
struct runq tdq_idle; /* Queue of IDLE threads. */
- Implement generic macros for producing KTR records that are compatible with src/tools/sched/schedgraph.py. This allows developers to quickly create a graphical view of ktr data for any resource in the system. - Add sched_tdname() and the pcpu field 'name' for quickly and uniformly identifying records associated with a thread or cpu. - Reimplement the KTR_SCHED traces using the new generic facility. Obtained from: attilio Discussed with: jhb Sponsored by: Nokia
2009-01-17 07:17:57 +00:00
char tdq_name[TDQ_NAME_LEN];
#ifdef KTR
char tdq_loadname[TDQ_LOADNAME_LEN];
#endif
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
} __aligned(64);
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
- Add a metric to describe how busy a processor has been over the last two ticks by counting the number of switches and the load when sched_clock() is called. - If the busy metric exceeds a threshold allow the idle thread to spin waiting for new work for a brief period to avoid using IPIs. This reduces the cost on the sender and receiver as well as reducing wakeup latency considerably when it works. Sponsored by: Nokia
2008-04-17 09:56:01 +00:00
/* Idle thread states and config. */
#define TDQ_RUNNING 1
#define TDQ_IDLE 2
Major revamp of ULE's cpu load balancing: - Switch back to direct modification of remote CPU run queues. This added a lot of complexity with questionable gain. It's easy enough to reimplement if it's shown to help on huge machines. - Re-implement the old tdq_transfer() call as tdq_pickidle(). Change sched_add() so we have selectable cpu choosers and simplify the logic a bit here. - Implement tdq_pickpri() as the new default cpu chooser. This algorithm is similar to Solaris in that it tries to always run the threads with the best priorities. It is actually slightly more complex than solaris's algorithm because we also tend to favor the local cpu over other cpus which has a boost in latency but also potentially enables cache sharing between the waking thread and the woken thread. - Add a bunch of tunables that can be used to measure effects of different load balancing strategies. Most of these will go away once the algorithm is more definite. - Add a new mechanism to steal threads from busy cpus when we idle. This is enabled with kern.sched.steal_busy and kern.sched.busy_thresh. The threshold is the required length of a tdq's run queue before another cpu will be able to steal runnable threads. This prevents most queue imbalances that contribute the long latencies.
2007-01-19 21:56:08 +00:00
- Add support for CPU groups to ule. All SMT cores on the same physical cpu are added to a group. - Don't place a cpu into the kseq_idle bitmask until all cpus in that group have idled. - Prefer idle groups over idle group members in the new kseq_transfer() function. In this way we will prefer to balance load across full cores rather than add further load a partial core. - Before a cpu goes idle, check the other group members for threads. Since SMT cpus may freely share threads, this is cheap. - SMT cores may be individually pinned and bound to now. This contrasts the old mechanism where binding or pinning would have allowed a thread to run on any available cpu. - Remove some unnecessary logic from sched_switch(). Priority propagation should be properly taken care of in sched_prio() now.
2003-12-11 03:57:10 +00:00
#ifdef SMP
Introduce a new sysctl, kern.sched.topology_spec, that returns an XML dump of detected ULE CPU topology. This dump can be used to check the topology detection and for general system information. An example of CPU topology dump is: kern.sched.topology_spec: <groups> <group level="1" cache-level="0"> <cpu count="8" mask="0xff">0, 1, 2, 3, 4, 5, 6, 7</cpu> <flags></flags> <children> <group level="2" cache-level="0"> <cpu count="4" mask="0xf">0, 1, 2, 3</cpu> <flags></flags> </group> <group level="2" cache-level="0"> <cpu count="4" mask="0xf0">4, 5, 6, 7</cpu> <flags></flags> </group> </children> </group> </groups> Reviewed by: jeff Approved by: gnn (mentor)
2008-10-29 13:36:23 +00:00
struct cpu_group *cpu_top; /* CPU topology */
Major revamp of ULE's cpu load balancing: - Switch back to direct modification of remote CPU run queues. This added a lot of complexity with questionable gain. It's easy enough to reimplement if it's shown to help on huge machines. - Re-implement the old tdq_transfer() call as tdq_pickidle(). Change sched_add() so we have selectable cpu choosers and simplify the logic a bit here. - Implement tdq_pickpri() as the new default cpu chooser. This algorithm is similar to Solaris in that it tries to always run the threads with the best priorities. It is actually slightly more complex than solaris's algorithm because we also tend to favor the local cpu over other cpus which has a boost in latency but also potentially enables cache sharing between the waking thread and the woken thread. - Add a bunch of tunables that can be used to measure effects of different load balancing strategies. Most of these will go away once the algorithm is more definite. - Add a new mechanism to steal threads from busy cpus when we idle. This is enabled with kern.sched.steal_busy and kern.sched.busy_thresh. The threshold is the required length of a tdq's run queue before another cpu will be able to steal runnable threads. This prevents most queue imbalances that contribute the long latencies.
2007-01-19 21:56:08 +00:00
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
#define SCHED_AFFINITY_DEFAULT (max(1, hz / 1000))
#define SCHED_AFFINITY(ts, t) ((ts)->ts_rltick > ticks - ((t) * affinity))
Major revamp of ULE's cpu load balancing: - Switch back to direct modification of remote CPU run queues. This added a lot of complexity with questionable gain. It's easy enough to reimplement if it's shown to help on huge machines. - Re-implement the old tdq_transfer() call as tdq_pickidle(). Change sched_add() so we have selectable cpu choosers and simplify the logic a bit here. - Implement tdq_pickpri() as the new default cpu chooser. This algorithm is similar to Solaris in that it tries to always run the threads with the best priorities. It is actually slightly more complex than solaris's algorithm because we also tend to favor the local cpu over other cpus which has a boost in latency but also potentially enables cache sharing between the waking thread and the woken thread. - Add a bunch of tunables that can be used to measure effects of different load balancing strategies. Most of these will go away once the algorithm is more definite. - Add a new mechanism to steal threads from busy cpus when we idle. This is enabled with kern.sched.steal_busy and kern.sched.busy_thresh. The threshold is the required length of a tdq's run queue before another cpu will be able to steal runnable threads. This prevents most queue imbalances that contribute the long latencies.
2007-01-19 21:56:08 +00:00
/*
* Run-time tunables.
*/
- Refine the load balancer to improve buildkernel times on dual core machines. - Leave the long-term load balancer running by default once per second. - Enable stealing load from the idle thread only when the remote processor has more than two transferable tasks. Setting this to one further improves buildworld. Setting it higher improves mysql. - Remove the bogus pick_zero option. I had not intended to commit this. - Entirely disallow migration for threads with SRQ_YIELDING set. This balances out the extra migration allowed for with the load balancers. It also makes pick_pri perform better as I had anticipated. Tested by: Dmitry Morozovsky <marck@rinet.ru> Approved by: re
2007-07-19 20:03:15 +00:00
static int rebalance = 1;
- Move the rebalancer back into hardclock to prevent potential softclock starvation caused by unbalanced interrupt loads. - Change the rebalancer to work on stathz ticks but retain randomization. - Simplify locking in tdq_idled() to use the tdq_lock_pair() rather than complex sequences of locks to avoid deadlock. Reported by: kris Approved by: re
2007-10-02 00:36:06 +00:00
static int balance_interval = 128; /* Default set in sched_initticks(). */
Major revamp of ULE's cpu load balancing: - Switch back to direct modification of remote CPU run queues. This added a lot of complexity with questionable gain. It's easy enough to reimplement if it's shown to help on huge machines. - Re-implement the old tdq_transfer() call as tdq_pickidle(). Change sched_add() so we have selectable cpu choosers and simplify the logic a bit here. - Implement tdq_pickpri() as the new default cpu chooser. This algorithm is similar to Solaris in that it tries to always run the threads with the best priorities. It is actually slightly more complex than solaris's algorithm because we also tend to favor the local cpu over other cpus which has a boost in latency but also potentially enables cache sharing between the waking thread and the woken thread. - Add a bunch of tunables that can be used to measure effects of different load balancing strategies. Most of these will go away once the algorithm is more definite. - Add a new mechanism to steal threads from busy cpus when we idle. This is enabled with kern.sched.steal_busy and kern.sched.busy_thresh. The threshold is the required length of a tdq's run queue before another cpu will be able to steal runnable threads. This prevents most queue imbalances that contribute the long latencies.
2007-01-19 21:56:08 +00:00
static int affinity;
- Refine the load balancer to improve buildkernel times on dual core machines. - Leave the long-term load balancer running by default once per second. - Enable stealing load from the idle thread only when the remote processor has more than two transferable tasks. Setting this to one further improves buildworld. Setting it higher improves mysql. - Remove the bogus pick_zero option. I had not intended to commit this. - Entirely disallow migration for threads with SRQ_YIELDING set. This balances out the extra migration allowed for with the load balancers. It also makes pick_pri perform better as I had anticipated. Tested by: Dmitry Morozovsky <marck@rinet.ru> Approved by: re
2007-07-19 20:03:15 +00:00
static int steal_idle = 1;
static int steal_thresh = 2;
Decrease latency by not wrapping the idle loop's potentially lengthy search for a thread to steal inside a critical section. Since this allows the search to be preempted, restart the search if preemption happens since the search results found earlier may no longer be valid. Decrease the latency of starting a thread that may be assigned to this CPU during the search by polling for incoming threads during the search and switching to that thread instead of continuing the search. Test for stale search results and restart the search before going through the expense of calling tdq_lock_pair(). Retry some tests after grabbing the locks since things may have changed while waiting to get both locks. Eliminate special case handling for stealing from an SMT peer that uses 1 as the steal threshold. This can only succeed if a thread has been assigned but our SMT peer has not yet started executing it. This is quite rare and when it happens the other SMT thread is generally waiting for the same tdq lock that we hold. Basically both SMT threads are racing to grab the same spin lock. Add the kern.sched.always_steal knob from a ULE patch by jeff@. Incorporate another idea from Jeff's ULE patch. If the sched_switch() detects that the CPU is about to go idle, try to steal a thread before switching to the idle thread. Since the search for a thread to steal has to be done inside a critical section in this context, limit the impact on latency by adding the knob kern.sched.trysteal_limit to limit the topological distance of the search and don't restart the search if we detect stale results. If this search can't find an stealable thread, the idle loop can do a more complete search. Also poll for threads being assigned to this CPU during the search and switch to them instead of continuing the search. This change is responsibile for the majority of the improvement in parallel buildworld times. In sched_balance_group() change the minimum threshold from stealing a thread from 1 to 2. Poaching a newly assigned thread from a CPU that is waking up hasn't yet switched to that thread from idle is likely very rare and is likely to have the same lock race as is seen when stealing threads in the idle loop. Also use tdq_notify() to kick the destintation CPU instead of always sending an IPI. Update a stale comment, the number of transferable threads is not calculated. Reviewed by: kib (earlier version) Comments by: avg, jeff, mav MFC after: 1 month Differential Revision: https://reviews.freebsd.org/D12130
2018-02-23 00:12:51 +00:00
static int always_steal = 0;
static int trysteal_limit = 2;
- Add support for CPU groups to ule. All SMT cores on the same physical cpu are added to a group. - Don't place a cpu into the kseq_idle bitmask until all cpus in that group have idled. - Prefer idle groups over idle group members in the new kseq_transfer() function. In this way we will prefer to balance load across full cores rather than add further load a partial core. - Before a cpu goes idle, check the other group members for threads. Since SMT cpus may freely share threads, this is cheap. - SMT cores may be individually pinned and bound to now. This contrasts the old mechanism where binding or pinning would have allowed a thread to run on any available cpu. - Remove some unnecessary logic from sched_switch(). Priority propagation should be properly taken care of in sched_prio() now.
2003-12-11 03:57:10 +00:00
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
/*
- Clean up a bit after the most recent KSE restructuring.
2006-12-29 10:37:07 +00:00
* One thread queue per processor.
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
*/
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
static struct tdq tdq_cpu[MAXCPU];
- Move the rebalancer back into hardclock to prevent potential softclock starvation caused by unbalanced interrupt loads. - Change the rebalancer to work on stathz ticks but retain randomization. - Simplify locking in tdq_idled() to use the tdq_lock_pair() rather than complex sequences of locks to avoid deadlock. Reported by: kris Approved by: re
2007-10-02 00:36:06 +00:00
static struct tdq *balance_tdq;
static int balance_ticks;
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
static DPCPU_DEFINE(uint32_t, randomval);
- Run sched_balance() and sched_balance_groups() from hardclock via sched_clock() rather than using callouts. This means we no longer have to take the load of the callout thread into consideration while balancing and should make the balancing decisions simpler and more accurate. Tested on: x86/UP, amd64/SMP
2004-06-02 05:46:48 +00:00
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
#define TDQ_SELF() (&tdq_cpu[PCPU_GET(cpuid)])
#define TDQ_CPU(x) (&tdq_cpu[(x)])
- Share scheduler locks between hyper-threaded cores to protect the tdq_group structure. Hyper-threaded cores won't really benefit from seperate locks anyway. - Seperate out the migration case from sched_switch to simplify the main switch code. We only migrate here if called via sched_bind(). - When preempted place the preempted thread back in the same queue at the head. - Improve the cpu group and topology infrastructure. Tested by: many on current@ Approved by: re
2007-08-03 23:38:46 +00:00
#define TDQ_ID(x) ((int)((x) - tdq_cpu))
- Add support for CPU groups to ule. All SMT cores on the same physical cpu are added to a group. - Don't place a cpu into the kseq_idle bitmask until all cpus in that group have idled. - Prefer idle groups over idle group members in the new kseq_transfer() function. In this way we will prefer to balance load across full cores rather than add further load a partial core. - Before a cpu goes idle, check the other group members for threads. Since SMT cpus may freely share threads, this is cheap. - SMT cores may be individually pinned and bound to now. This contrasts the old mechanism where binding or pinning would have allowed a thread to run on any available cpu. - Remove some unnecessary logic from sched_switch(). Priority propagation should be properly taken care of in sched_prio() now.
2003-12-11 03:57:10 +00:00
#else /* !SMP */
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
static struct tdq tdq_cpu;
- Run sched_balance() and sched_balance_groups() from hardclock via sched_clock() rather than using callouts. This means we no longer have to take the load of the callout thread into consideration while balancing and should make the balancing decisions simpler and more accurate. Tested on: x86/UP, amd64/SMP
2004-06-02 05:46:48 +00:00
- Define TDQ_ID() for the !SMP case. - Default pick_pri to off. It is not faster in most cases.
2007-06-05 02:53:51 +00:00
#define TDQ_ID(x) (0)
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
#define TDQ_SELF() (&tdq_cpu)
#define TDQ_CPU(x) (&tdq_cpu)
- Use ksq_load as the authoritive count of kses on the pair of kseqs for sched_runnable() et all. - Remove some dead code in sched_clock(). - Define two macros KSEQ_SELF() and KSEQ_CPU() for getting the kseq of the current cpu or some alternate cpu. - Start introducing kseq_() functions, such as kseq_choose() and kseq_setup().
2003-01-29 07:00:51 +00:00
#endif
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
#define TDQ_LOCK_ASSERT(t, type) mtx_assert(TDQ_LOCKPTR((t)), (type))
#define TDQ_LOCK(t) mtx_lock_spin(TDQ_LOCKPTR((t)))
#define TDQ_LOCK_FLAGS(t, f) mtx_lock_spin_flags(TDQ_LOCKPTR((t)), (f))
#define TDQ_UNLOCK(t) mtx_unlock_spin(TDQ_LOCKPTR((t)))
Rework the known mutexes to benefit about staying on their own cache line in order to avoid manual frobbing but using struct mtx_padalign. The sole exception being nvme and sxfge drivers, where the author redefined CACHE_LINE_SIZE manually, so they need to be analyzed and dealt with separately. Reviwed by: jimharris, alc
2012-10-31 18:07:18 +00:00
#define TDQ_LOCKPTR(t) ((struct mtx *)(&(t)->tdq_lock))
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
Make KSE a kernel option, turned on by default in all GENERIC kernel configs except sun4v (which doesn't process signals properly with KSE). Reviewed by: davidxu@
2006-10-26 21:42:22 +00:00
static void sched_priority(struct thread *);
- Don't SLOT_USE() in the preempt case, sched_add() has already taken the slot for us. Previously, we would take two slots on every preempt, and setrunqueue() would fix it up for us in the non threaded case. The threaded case was simply broken. - Clean up flags, prototypes, comments.
2005-06-04 09:23:28 +00:00
static void sched_thread_priority(struct thread *, u_char);
Make KSE a kernel option, turned on by default in all GENERIC kernel configs except sun4v (which doesn't process signals properly with KSE). Reviewed by: davidxu@
2006-10-26 21:42:22 +00:00
static int sched_interact_score(struct thread *);
static void sched_interact_update(struct thread *);
static void sched_interact_fork(struct thread *);
Rewrite thread CPU usage percentage math to not depend on periodic calls with HZ rate through the sched_tick() calls from hardclock(). Potentially it can be used to improve precision, but now it is just minus one more reason to call hardclock() for every HZ tick on every active CPU. SCHED_4BSD never used sched_tick(), but keep it in place for now, as at least SCHED_FBFS existing in patches out of the tree depends on it. MFC after: 1 month
2012-03-13 08:18:54 +00:00
static void sched_pctcpu_update(struct td_sched *, int);
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
- Make some context switches conditional on SCHED_STRICT_RESCHED. This may have some negative effect on interactivity but it yields great perf. gains. This also brings the conditions under which ULE context switches inline with SCHED_4BSD. - Define some new kseq_* functions for manipulating the run queue. - Add a new kseq member ksq_rslices and ksq_bload. rslices is the sum of the slices of runnable kses. This will be used for push load balance decisions. bload is the number of threads blocked waiting on IO.
2003-02-03 05:30:07 +00:00
/* Operations on per processor queues */
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
static struct thread *tdq_choose(struct tdq *);
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
static void tdq_setup(struct tdq *);
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
static void tdq_load_add(struct tdq *, struct thread *);
static void tdq_load_rem(struct tdq *, struct thread *);
static __inline void tdq_runq_add(struct tdq *, struct thread *, int);
static __inline void tdq_runq_rem(struct tdq *, struct thread *);
- Add an implementation of sched_preempt() that avoids excessive IPIs. - Normalize the preemption/ipi setting code by introducing sched_shouldpreempt() so the logical is identical and not repeated between tdq_notify() and sched_setpreempt(). - In tdq_notify() don't set NEEDRESCHED as we may not actually own the thread lock this could have caused us to lose td_flags settings. - Garbage collect some tunables that are no longer relevant.
2008-03-10 01:32:01 +00:00
static inline int sched_shouldpreempt(int, int, int);
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
void tdq_print(int cpu);
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
static void runq_print(struct runq *rq);
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
static void tdq_add(struct tdq *, struct thread *, int);
- Make some context switches conditional on SCHED_STRICT_RESCHED. This may have some negative effect on interactivity but it yields great perf. gains. This also brings the conditions under which ULE context switches inline with SCHED_4BSD. - Define some new kseq_* functions for manipulating the run queue. - Add a new kseq member ksq_rslices and ksq_bload. rslices is the sum of the slices of runnable kses. This will be used for push load balance decisions. bload is the number of threads blocked waiting on IO.
2003-02-03 05:30:07 +00:00
#ifdef SMP
Decrease latency by not wrapping the idle loop's potentially lengthy search for a thread to steal inside a critical section. Since this allows the search to be preempted, restart the search if preemption happens since the search results found earlier may no longer be valid. Decrease the latency of starting a thread that may be assigned to this CPU during the search by polling for incoming threads during the search and switching to that thread instead of continuing the search. Test for stale search results and restart the search before going through the expense of calling tdq_lock_pair(). Retry some tests after grabbing the locks since things may have changed while waiting to get both locks. Eliminate special case handling for stealing from an SMT peer that uses 1 as the steal threshold. This can only succeed if a thread has been assigned but our SMT peer has not yet started executing it. This is quite rare and when it happens the other SMT thread is generally waiting for the same tdq lock that we hold. Basically both SMT threads are racing to grab the same spin lock. Add the kern.sched.always_steal knob from a ULE patch by jeff@. Incorporate another idea from Jeff's ULE patch. If the sched_switch() detects that the CPU is about to go idle, try to steal a thread before switching to the idle thread. Since the search for a thread to steal has to be done inside a critical section in this context, limit the impact on latency by adding the knob kern.sched.trysteal_limit to limit the topological distance of the search and don't restart the search if we detect stale results. If this search can't find an stealable thread, the idle loop can do a more complete search. Also poll for threads being assigned to this CPU during the search and switch to them instead of continuing the search. This change is responsibile for the majority of the improvement in parallel buildworld times. In sched_balance_group() change the minimum threshold from stealing a thread from 1 to 2. Poaching a newly assigned thread from a CPU that is waking up hasn't yet switched to that thread from idle is likely very rare and is likely to have the same lock race as is seen when stealing threads in the idle loop. Also use tdq_notify() to kick the destintation CPU instead of always sending an IPI. Update a stale comment, the number of transferable threads is not calculated. Reviewed by: kib (earlier version) Comments by: avg, jeff, mav MFC after: 1 month Differential Revision: https://reviews.freebsd.org/D12130
2018-02-23 00:12:51 +00:00
static struct thread *tdq_move(struct tdq *, struct tdq *);
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
static int tdq_idled(struct tdq *);
Revert r313814 and r313816 Something evidently got mangled in my git tree in between testing and review, as an old and broken version of the patch was apparently submitted to svn. Revert this while I work out what went wrong. Reported by: tuexen Pointy hat to: rstone
2017-02-16 21:18:31 +00:00
static void tdq_notify(struct tdq *, struct thread *);
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
static struct thread *tdq_steal(struct tdq *, int);
static struct thread *runq_steal(struct runq *, int);
static int sched_pickcpu(struct thread *, int);
- Move the rebalancer back into hardclock to prevent potential softclock starvation caused by unbalanced interrupt loads. - Change the rebalancer to work on stathz ticks but retain randomization. - Simplify locking in tdq_idled() to use the tdq_lock_pair() rather than complex sequences of locks to avoid deadlock. Reported by: kris Approved by: re
2007-10-02 00:36:06 +00:00
static void sched_balance(void);
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
static int sched_balance_pair(struct tdq *, struct tdq *);
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
static inline struct tdq *sched_setcpu(struct thread *, int, int);
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
static inline void thread_unblock_switch(struct thread *, struct mtx *);
- Share scheduler locks between hyper-threaded cores to protect the tdq_group structure. Hyper-threaded cores won't really benefit from seperate locks anyway. - Seperate out the migration case from sched_switch to simplify the main switch code. We only migrate here if called via sched_bind(). - When preempted place the preempted thread back in the same queue at the head. - Improve the cpu group and topology infrastructure. Tested by: many on current@ Approved by: re
2007-08-03 23:38:46 +00:00
static struct mtx *sched_switch_migrate(struct tdq *, struct thread *, int);
Introduce a new sysctl, kern.sched.topology_spec, that returns an XML dump of detected ULE CPU topology. This dump can be used to check the topology detection and for general system information. An example of CPU topology dump is: kern.sched.topology_spec: <groups> <group level="1" cache-level="0"> <cpu count="8" mask="0xff">0, 1, 2, 3, 4, 5, 6, 7</cpu> <flags></flags> <children> <group level="2" cache-level="0"> <cpu count="4" mask="0xf">0, 1, 2, 3</cpu> <flags></flags> </group> <group level="2" cache-level="0"> <cpu count="4" mask="0xf0">4, 5, 6, 7</cpu> <flags></flags> </group> </children> </group> </groups> Reviewed by: jeff Approved by: gnn (mentor)
2008-10-29 13:36:23 +00:00
static int sysctl_kern_sched_topology_spec(SYSCTL_HANDLER_ARGS);
static int sysctl_kern_sched_topology_spec_internal(struct sbuf *sb,
struct cpu_group *cg, int indent);
- Make some context switches conditional on SCHED_STRICT_RESCHED. This may have some negative effect on interactivity but it yields great perf. gains. This also brings the conditions under which ULE context switches inline with SCHED_4BSD. - Define some new kseq_* functions for manipulating the run queue. - Add a new kseq member ksq_rslices and ksq_bload. rslices is the sum of the slices of runnable kses. This will be used for push load balance decisions. bload is the number of threads blocked waiting on IO.
2003-02-03 05:30:07 +00:00
#endif
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
static void sched_setup(void *dummy);
In keeping with style(9)'s recommendations on macros, use a ';' after each SYSINIT() macro invocation. This makes a number of lightweight C parsers much happier with the FreeBSD kernel source, including cflow's prcc and lxr. MFC after: 1 month Discussed with: imp, rink
2008-03-16 10:58:09 +00:00
SYSINIT(sched_setup, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, sched_setup, NULL);
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
static void sched_initticks(void *dummy);
In keeping with style(9)'s recommendations on macros, use a ';' after each SYSINIT() macro invocation. This makes a number of lightweight C parsers much happier with the FreeBSD kernel source, including cflow's prcc and lxr. MFC after: 1 month Discussed with: imp, rink
2008-03-16 10:58:09 +00:00
SYSINIT(sched_initticks, SI_SUB_CLOCKS, SI_ORDER_THIRD, sched_initticks,
NULL);
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
Implement the DTrace sched provider. This implementation aims to be compatible with the sched provider implemented by Solaris and its open- source derivatives. Full documentation of the sched provider can be found on Oracle's DTrace wiki pages. Note that for compatibility with scripts originally written for Solaris, serveral probes are defined that will never fire. These probes are defined to fire when Solaris-specific features perform certain actions. As these features are not present in FreeBSD, the probes can never fire. Also, I have added a two probes that are not defined in Solaris, lend-pri and load-change. These probes have been added to make it possible to collect schedgraph data with DTrace. Finally, a few probes are defined in Solaris to take a cpuinfo_t * argument. As it was not immediately clear to me how to translate that to FreeBSD, currently those probes are passed NULL in place of a cpuinfo_t *. Sponsored by: Sandvine Incorporated MFC after: 2 weeks
2012-05-15 01:30:25 +00:00
SDT_PROVIDER_DEFINE(sched);
dtrace sdt: remove the ugly sname parameter of SDT_PROBE_DEFINE In its stead use the Solaris / illumos approach of emulating '-' (dash) in probe names with '__' (two consecutive underscores). Reviewed by: markj MFC after: 3 weeks
2013-11-26 08:46:27 +00:00
SDT_PROBE_DEFINE3(sched, , , change__pri, "struct thread *",
Implement the DTrace sched provider. This implementation aims to be compatible with the sched provider implemented by Solaris and its open- source derivatives. Full documentation of the sched provider can be found on Oracle's DTrace wiki pages. Note that for compatibility with scripts originally written for Solaris, serveral probes are defined that will never fire. These probes are defined to fire when Solaris-specific features perform certain actions. As these features are not present in FreeBSD, the probes can never fire. Also, I have added a two probes that are not defined in Solaris, lend-pri and load-change. These probes have been added to make it possible to collect schedgraph data with DTrace. Finally, a few probes are defined in Solaris to take a cpuinfo_t * argument. As it was not immediately clear to me how to translate that to FreeBSD, currently those probes are passed NULL in place of a cpuinfo_t *. Sponsored by: Sandvine Incorporated MFC after: 2 weeks
2012-05-15 01:30:25 +00:00
"struct proc *", "uint8_t");
dtrace sdt: remove the ugly sname parameter of SDT_PROBE_DEFINE In its stead use the Solaris / illumos approach of emulating '-' (dash) in probe names with '__' (two consecutive underscores). Reviewed by: markj MFC after: 3 weeks
2013-11-26 08:46:27 +00:00
SDT_PROBE_DEFINE3(sched, , , dequeue, "struct thread *",
Implement the DTrace sched provider. This implementation aims to be compatible with the sched provider implemented by Solaris and its open- source derivatives. Full documentation of the sched provider can be found on Oracle's DTrace wiki pages. Note that for compatibility with scripts originally written for Solaris, serveral probes are defined that will never fire. These probes are defined to fire when Solaris-specific features perform certain actions. As these features are not present in FreeBSD, the probes can never fire. Also, I have added a two probes that are not defined in Solaris, lend-pri and load-change. These probes have been added to make it possible to collect schedgraph data with DTrace. Finally, a few probes are defined in Solaris to take a cpuinfo_t * argument. As it was not immediately clear to me how to translate that to FreeBSD, currently those probes are passed NULL in place of a cpuinfo_t *. Sponsored by: Sandvine Incorporated MFC after: 2 weeks
2012-05-15 01:30:25 +00:00
"struct proc *", "void *");
dtrace sdt: remove the ugly sname parameter of SDT_PROBE_DEFINE In its stead use the Solaris / illumos approach of emulating '-' (dash) in probe names with '__' (two consecutive underscores). Reviewed by: markj MFC after: 3 weeks
2013-11-26 08:46:27 +00:00
SDT_PROBE_DEFINE4(sched, , , enqueue, "struct thread *",
Implement the DTrace sched provider. This implementation aims to be compatible with the sched provider implemented by Solaris and its open- source derivatives. Full documentation of the sched provider can be found on Oracle's DTrace wiki pages. Note that for compatibility with scripts originally written for Solaris, serveral probes are defined that will never fire. These probes are defined to fire when Solaris-specific features perform certain actions. As these features are not present in FreeBSD, the probes can never fire. Also, I have added a two probes that are not defined in Solaris, lend-pri and load-change. These probes have been added to make it possible to collect schedgraph data with DTrace. Finally, a few probes are defined in Solaris to take a cpuinfo_t * argument. As it was not immediately clear to me how to translate that to FreeBSD, currently those probes are passed NULL in place of a cpuinfo_t *. Sponsored by: Sandvine Incorporated MFC after: 2 weeks
2012-05-15 01:30:25 +00:00
"struct proc *", "void *", "int");
dtrace sdt: remove the ugly sname parameter of SDT_PROBE_DEFINE In its stead use the Solaris / illumos approach of emulating '-' (dash) in probe names with '__' (two consecutive underscores). Reviewed by: markj MFC after: 3 weeks
2013-11-26 08:46:27 +00:00
SDT_PROBE_DEFINE4(sched, , , lend__pri, "struct thread *",
Implement the DTrace sched provider. This implementation aims to be compatible with the sched provider implemented by Solaris and its open- source derivatives. Full documentation of the sched provider can be found on Oracle's DTrace wiki pages. Note that for compatibility with scripts originally written for Solaris, serveral probes are defined that will never fire. These probes are defined to fire when Solaris-specific features perform certain actions. As these features are not present in FreeBSD, the probes can never fire. Also, I have added a two probes that are not defined in Solaris, lend-pri and load-change. These probes have been added to make it possible to collect schedgraph data with DTrace. Finally, a few probes are defined in Solaris to take a cpuinfo_t * argument. As it was not immediately clear to me how to translate that to FreeBSD, currently those probes are passed NULL in place of a cpuinfo_t *. Sponsored by: Sandvine Incorporated MFC after: 2 weeks
2012-05-15 01:30:25 +00:00
"struct proc *", "uint8_t", "struct thread *");
dtrace sdt: remove the ugly sname parameter of SDT_PROBE_DEFINE In its stead use the Solaris / illumos approach of emulating '-' (dash) in probe names with '__' (two consecutive underscores). Reviewed by: markj MFC after: 3 weeks
2013-11-26 08:46:27 +00:00
SDT_PROBE_DEFINE2(sched, , , load__change, "int", "int");
SDT_PROBE_DEFINE2(sched, , , off__cpu, "struct thread *",
Implement the DTrace sched provider. This implementation aims to be compatible with the sched provider implemented by Solaris and its open- source derivatives. Full documentation of the sched provider can be found on Oracle's DTrace wiki pages. Note that for compatibility with scripts originally written for Solaris, serveral probes are defined that will never fire. These probes are defined to fire when Solaris-specific features perform certain actions. As these features are not present in FreeBSD, the probes can never fire. Also, I have added a two probes that are not defined in Solaris, lend-pri and load-change. These probes have been added to make it possible to collect schedgraph data with DTrace. Finally, a few probes are defined in Solaris to take a cpuinfo_t * argument. As it was not immediately clear to me how to translate that to FreeBSD, currently those probes are passed NULL in place of a cpuinfo_t *. Sponsored by: Sandvine Incorporated MFC after: 2 weeks
2012-05-15 01:30:25 +00:00
"struct proc *");
dtrace sdt: remove the ugly sname parameter of SDT_PROBE_DEFINE In its stead use the Solaris / illumos approach of emulating '-' (dash) in probe names with '__' (two consecutive underscores). Reviewed by: markj MFC after: 3 weeks
2013-11-26 08:46:27 +00:00
SDT_PROBE_DEFINE(sched, , , on__cpu);
SDT_PROBE_DEFINE(sched, , , remain__cpu);
SDT_PROBE_DEFINE2(sched, , , surrender, "struct thread *",
Implement the DTrace sched provider. This implementation aims to be compatible with the sched provider implemented by Solaris and its open- source derivatives. Full documentation of the sched provider can be found on Oracle's DTrace wiki pages. Note that for compatibility with scripts originally written for Solaris, serveral probes are defined that will never fire. These probes are defined to fire when Solaris-specific features perform certain actions. As these features are not present in FreeBSD, the probes can never fire. Also, I have added a two probes that are not defined in Solaris, lend-pri and load-change. These probes have been added to make it possible to collect schedgraph data with DTrace. Finally, a few probes are defined in Solaris to take a cpuinfo_t * argument. As it was not immediately clear to me how to translate that to FreeBSD, currently those probes are passed NULL in place of a cpuinfo_t *. Sponsored by: Sandvine Incorporated MFC after: 2 weeks
2012-05-15 01:30:25 +00:00
"struct proc *");
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* Print the threads waiting on a run-queue.
*/
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
static void
runq_print(struct runq *rq)
{
struct rqhead *rqh;
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
struct thread *td;
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
int pri;
int j;
int i;
for (i = 0; i < RQB_LEN; i++) {
printf("\t\trunq bits %d 0x%zx\n",
i, rq->rq_status.rqb_bits[i]);
for (j = 0; j < RQB_BPW; j++)
if (rq->rq_status.rqb_bits[i] & (1ul << j)) {
pri = j + (i << RQB_L2BPW);
rqh = &rq->rq_queues[pri];
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
TAILQ_FOREACH(td, rqh, td_runq) {
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
printf("\t\t\ttd %p(%s) priority %d rqindex %d pri %d\n",
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
td, td->td_name, td->td_priority,
td->td_rqindex, pri);
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
}
}
}
}
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* Print the status of a per-cpu thread queue. Should be a ddb show cmd.
*/
- Add a SYSCTL node for the ule scheduler. - Allow user adjustable min and max time slices (suggested by hiten). - Change the SLP_RUN_MAX to 100ms from 2 seconds so that we learn whether a process is interactive or not much more quickly. - Place a process on the current run queue if it is interactive or if it is running at an interrupt thread priority due to priority prop. - Use the 'current' timeshare queue for interrupt threads, realtime threads, and idle threads that are running at higher priority due to priority prop. This fixes problems where priorities would have been elevated but we would not check the timeshare run queue until other lower priority tasks were no longer runnable. - Keep an array of loads indexed by the priority class as well as a global load. - Keep an bucket of nice values with a count of the number of kses currently runnable with that nice value. - Keep track of the minimum nice value of any running thread. - Remove the unused short term sleep accounting. I was attempting to use this for load balancing but it didn't work out. - Define a kseq_print() for use with debugging. - Add KTR debugging at useful places so we can easily debug slice and priority assignment. - Decouple the runq assignment from the kseq assignment. kseq_add now keeps track of statistics. This is done so that the nice and load is still tracked for the currently running process. Previously if a niced process was added while a non nice process was running the niced process would still get a slice since it was not aware of the unnice process. - Make adjustments for the sched api changes.
2003-04-11 03:47:14 +00:00
void
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
tdq_print(int cpu)
- Make some context switches conditional on SCHED_STRICT_RESCHED. This may have some negative effect on interactivity but it yields great perf. gains. This also brings the conditions under which ULE context switches inline with SCHED_4BSD. - Define some new kseq_* functions for manipulating the run queue. - Add a new kseq member ksq_rslices and ksq_bload. rslices is the sum of the slices of runnable kses. This will be used for push load balance decisions. bload is the number of threads blocked waiting on IO.
2003-02-03 05:30:07 +00:00
{
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
struct tdq *tdq;
- Keep seperate statistics and run queues for different scheduling classes. - Treat each class specially in kseq_{choose,add,rem}. Let the rest of the code be less aware of scheduling classes. - Skip the interactivity calculation for non TIMESHARE ksegrps. - Move slice and runq selection into kseq_add(). Uninline it now that it's big.
2003-04-03 00:29:28 +00:00
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
tdq = TDQ_CPU(cpu);
- Keep seperate statistics and run queues for different scheduling classes. - Treat each class specially in kseq_{choose,add,rem}. Let the rest of the code be less aware of scheduling classes. - Skip the interactivity calculation for non TIMESHARE ksegrps. - Move slice and runq selection into kseq_add(). Uninline it now that it's big.
2003-04-03 00:29:28 +00:00
- Share scheduler locks between hyper-threaded cores to protect the tdq_group structure. Hyper-threaded cores won't really benefit from seperate locks anyway. - Seperate out the migration case from sched_switch to simplify the main switch code. We only migrate here if called via sched_bind(). - When preempted place the preempted thread back in the same queue at the head. - Improve the cpu group and topology infrastructure. Tested by: many on current@ Approved by: re
2007-08-03 23:38:46 +00:00
printf("tdq %d:\n", TDQ_ID(tdq));
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
printf("\tlock %p\n", TDQ_LOCKPTR(tdq));
printf("\tLock name: %s\n", tdq->tdq_name);
- Clean up a bit after the most recent KSE restructuring.
2006-12-29 10:37:07 +00:00
printf("\tload: %d\n", tdq->tdq_load);
- Add a metric to describe how busy a processor has been over the last two ticks by counting the number of switches and the load when sched_clock() is called. - If the busy metric exceeds a threshold allow the idle thread to spin waiting for new work for a brief period to avoid using IPIs. This reduces the cost on the sender and receiver as well as reducing wakeup latency considerably when it works. Sponsored by: Nokia
2008-04-17 09:56:01 +00:00
printf("\tswitch cnt: %d\n", tdq->tdq_switchcnt);
printf("\told switch cnt: %d\n", tdq->tdq_oldswitchcnt);
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
printf("\ttimeshare idx: %d\n", tdq->tdq_idx);
- Only allow the tdq_idx to increase by one each tick rather than up to the most recently chosen index. This significantly improves nice behavior. This allows a lower priority thread to run some multiple of times before the higher priority thread makes it to the front of the queue. A nice +20 cpu hog now only gets ~5% of the cpu when running with a nice 0 cpu hog and about 1.5% with a nice -20 hog. A nice difference of 1 makes a 4% difference in cpu usage between two hogs. - Track a seperate insert and removal index. When the removal index is empty it is updated to point at the current insert index. - Don't remove and re-add a thread to the runq when it is being adjusted down in priority. - Pull some conditional code out of sched_tick(). It's looking a bit large now.
2007-01-04 12:16:19 +00:00
printf("\ttimeshare ridx: %d\n", tdq->tdq_ridx);
- Add a metric to describe how busy a processor has been over the last two ticks by counting the number of switches and the load when sched_clock() is called. - If the busy metric exceeds a threshold allow the idle thread to spin waiting for new work for a brief period to avoid using IPIs. This reduces the cost on the sender and receiver as well as reducing wakeup latency considerably when it works. Sponsored by: Nokia
2008-04-17 09:56:01 +00:00
printf("\tload transferable: %d\n", tdq->tdq_transferable);
printf("\tlowest priority: %d\n", tdq->tdq_lowpri);
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
printf("\trealtime runq:\n");
runq_print(&tdq->tdq_realtime);
printf("\ttimeshare runq:\n");
runq_print(&tdq->tdq_timeshare);
printf("\tidle runq:\n");
runq_print(&tdq->tdq_idle);
- Add a SYSCTL node for the ule scheduler. - Allow user adjustable min and max time slices (suggested by hiten). - Change the SLP_RUN_MAX to 100ms from 2 seconds so that we learn whether a process is interactive or not much more quickly. - Place a process on the current run queue if it is interactive or if it is running at an interrupt thread priority due to priority prop. - Use the 'current' timeshare queue for interrupt threads, realtime threads, and idle threads that are running at higher priority due to priority prop. This fixes problems where priorities would have been elevated but we would not check the timeshare run queue until other lower priority tasks were no longer runnable. - Keep an array of loads indexed by the priority class as well as a global load. - Keep an bucket of nice values with a count of the number of kses currently runnable with that nice value. - Keep track of the minimum nice value of any running thread. - Remove the unused short term sleep accounting. I was attempting to use this for load balancing but it didn't work out. - Define a kseq_print() for use with debugging. - Add KTR debugging at useful places so we can easily debug slice and priority assignment. - Decouple the runq assignment from the kseq assignment. kseq_add now keeps track of statistics. This is done so that the nice and load is still tracked for the currently running process. Previously if a niced process was added while a non nice process was running the niced process would still get a slice since it was not aware of the unnice process. - Make adjustments for the sched api changes.
2003-04-11 03:47:14 +00:00
}
- Keep seperate statistics and run queues for different scheduling classes. - Treat each class specially in kseq_{choose,add,rem}. Let the rest of the code be less aware of scheduling classes. - Skip the interactivity calculation for non TIMESHARE ksegrps. - Move slice and runq selection into kseq_add(). Uninline it now that it's big.
2003-04-03 00:29:28 +00:00
- Add an implementation of sched_preempt() that avoids excessive IPIs. - Normalize the preemption/ipi setting code by introducing sched_shouldpreempt() so the logical is identical and not repeated between tdq_notify() and sched_setpreempt(). - In tdq_notify() don't set NEEDRESCHED as we may not actually own the thread lock this could have caused us to lose td_flags settings. - Garbage collect some tunables that are no longer relevant.
2008-03-10 01:32:01 +00:00
static inline int
sched_shouldpreempt(int pri, int cpri, int remote)
{
/*
* If the new priority is not better than the current priority there is
* nothing to do.
*/
if (pri >= cpri)
return (0);
/*
* Always preempt idle.
*/
if (cpri >= PRI_MIN_IDLE)
return (1);
/*
* If preemption is disabled don't preempt others.
*/
if (preempt_thresh == 0)
return (0);
/*
* Preempt if we exceed the threshold.
*/
if (pri <= preempt_thresh)
return (1);
/*
Introduce two new helper macros to define the priority ranges used for interactive timeshare threads (PRI_*_INTERACTIVE) and non-interactive timeshare threads (PRI_*_BATCH) and use these instead of PRI_*_REALTIME and PRI_*_TIMESHARE. No functional change. Reviewed by: jeff
2011-01-13 14:22:27 +00:00
* If we're interactive or better and there is non-interactive
* or worse running preempt only remote processors.
- Add an implementation of sched_preempt() that avoids excessive IPIs. - Normalize the preemption/ipi setting code by introducing sched_shouldpreempt() so the logical is identical and not repeated between tdq_notify() and sched_setpreempt(). - In tdq_notify() don't set NEEDRESCHED as we may not actually own the thread lock this could have caused us to lose td_flags settings. - Garbage collect some tunables that are no longer relevant.
2008-03-10 01:32:01 +00:00
*/
Introduce two new helper macros to define the priority ranges used for interactive timeshare threads (PRI_*_INTERACTIVE) and non-interactive timeshare threads (PRI_*_BATCH) and use these instead of PRI_*_REALTIME and PRI_*_TIMESHARE. No functional change. Reviewed by: jeff
2011-01-13 14:22:27 +00:00
if (remote && pri <= PRI_MAX_INTERACT && cpri > PRI_MAX_INTERACT)
- Add an implementation of sched_preempt() that avoids excessive IPIs. - Normalize the preemption/ipi setting code by introducing sched_shouldpreempt() so the logical is identical and not repeated between tdq_notify() and sched_setpreempt(). - In tdq_notify() don't set NEEDRESCHED as we may not actually own the thread lock this could have caused us to lose td_flags settings. - Garbage collect some tunables that are no longer relevant.
2008-03-10 01:32:01 +00:00
return (1);
return (0);
}
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* Add a thread to the actual run-queue. Keeps transferable counts up to
* date with what is actually on the run-queue. Selects the correct
* queue position for timeshare threads.
*/
- Introduce kseq_runq_{add,rem}() which are used to insert and remove kses from the run queues. Also, on SMP, we track the transferable count here. Threads are transferable only as long as they are on the run queue. - Previously, we adjusted our load balancing based on the transferable count minus the number of actual cpus. This was done to account for the threads which were likely to be running. All of this logic is simpler now that transferable accounts for only those threads which can actually be taken. Updated various places in sched_add() and kseq_balance() to account for this. - Rename kseq_{add,rem} to kseq_load_{add,rem} to reflect what they're really doing. The load is accounted for seperately from the runq because the load is accounted for even as the thread is running. - Fix a bug in sched_class() where we weren't properly using the PRI_BASE() version of the kg_pri_class. - Add a large comment that describes the impact of a seemingly simple conditional in sched_add(). - Also in sched_add() check the transferable count and KSE_CAN_MIGRATE() prior to checking kseq_idle. This reduces the frequency of access for kseq_idle which is a shared resource.
2003-11-15 07:32:07 +00:00
static __inline void
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
tdq_runq_add(struct tdq *tdq, struct thread *td, int flags)
- Introduce kseq_runq_{add,rem}() which are used to insert and remove kses from the run queues. Also, on SMP, we track the transferable count here. Threads are transferable only as long as they are on the run queue. - Previously, we adjusted our load balancing based on the transferable count minus the number of actual cpus. This was done to account for the threads which were likely to be running. All of this logic is simpler now that transferable accounts for only those threads which can actually be taken. Updated various places in sched_add() and kseq_balance() to account for this. - Rename kseq_{add,rem} to kseq_load_{add,rem} to reflect what they're really doing. The load is accounted for seperately from the runq because the load is accounted for even as the thread is running. - Fix a bug in sched_class() where we weren't properly using the PRI_BASE() version of the kg_pri_class. - Add a large comment that describes the impact of a seemingly simple conditional in sched_add(). - Also in sched_add() check the transferable count and KSE_CAN_MIGRATE() prior to checking kseq_idle. This reduces the frequency of access for kseq_idle which is a shared resource.
2003-11-15 07:32:07 +00:00
{
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
struct td_sched *ts;
- Fix the invalid priority panics people are seeing by forcing tdq_runq_add to select the runq rather than hoping we set it properly when we adjusted the priority. This involves the same number of branches as before so should perform identically without the extra fragility. Tested by: bz Reviewed by: bz
2008-03-10 22:48:27 +00:00
u_char pri;
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
THREAD_LOCK_ASSERT(td, MA_OWNED);
Reduce ULE context switch time by over 25%. - Only calculate timeshare priorities once per tick or when a thread is woken from sleeping. - Keep the ts_runq pointer valid after all priority changes. - Call tdq_runq_add() directly from sched_switch() without passing in via tdq_add(). We don't need to adjust loads or runqs anymore. - Sort tdq and ts_sched according to utilization to improve cache behavior. Sponsored by: Nokia
2008-03-10 03:15:19 +00:00
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
pri = td->td_priority;
Get rid of struct proc p_sched and struct thread td_sched pointers. p_sched is unused. The struct td_sched is always co-allocated with the struct thread, except for the thread0. Avoid useless indirection, instead calculate td_sched location using simple pointer arithmetic in td_get_sched(9). For thread0, which is statically allocated, create a structure to emulate layout of the dynamic allocation. Reviewed by: jhb (previous version) Sponsored by: The FreeBSD Foundation Differential revision: https://reviews.freebsd.org/D6711
2016-06-05 17:04:03 +00:00
ts = td_get_sched(td);
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
TD_SET_RUNQ(td);
if (THREAD_CAN_MIGRATE(td)) {
- Clean up a bit after the most recent KSE restructuring.
2006-12-29 10:37:07 +00:00
tdq->tdq_transferable++;
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
ts->ts_flags |= TSF_XFERABLE;
- Add support for CPU groups to ule. All SMT cores on the same physical cpu are added to a group. - Don't place a cpu into the kseq_idle bitmask until all cpus in that group have idled. - Prefer idle groups over idle group members in the new kseq_transfer() function. In this way we will prefer to balance load across full cores rather than add further load a partial core. - Before a cpu goes idle, check the other group members for threads. Since SMT cpus may freely share threads, this is cheap. - SMT cores may be individually pinned and bound to now. This contrasts the old mechanism where binding or pinning would have allowed a thread to run on any available cpu. - Remove some unnecessary logic from sched_switch(). Priority propagation should be properly taken care of in sched_prio() now.
2003-12-11 03:57:10 +00:00
}
Introduce two new helper macros to define the priority ranges used for interactive timeshare threads (PRI_*_INTERACTIVE) and non-interactive timeshare threads (PRI_*_BATCH) and use these instead of PRI_*_REALTIME and PRI_*_TIMESHARE. No functional change. Reviewed by: jeff
2011-01-13 14:22:27 +00:00
if (pri < PRI_MIN_BATCH) {
- Fix the invalid priority panics people are seeing by forcing tdq_runq_add to select the runq rather than hoping we set it properly when we adjusted the priority. This involves the same number of branches as before so should perform identically without the extra fragility. Tested by: bz Reviewed by: bz
2008-03-10 22:48:27 +00:00
ts->ts_runq = &tdq->tdq_realtime;
Introduce two new helper macros to define the priority ranges used for interactive timeshare threads (PRI_*_INTERACTIVE) and non-interactive timeshare threads (PRI_*_BATCH) and use these instead of PRI_*_REALTIME and PRI_*_TIMESHARE. No functional change. Reviewed by: jeff
2011-01-13 14:22:27 +00:00
} else if (pri <= PRI_MAX_BATCH) {
- Fix the invalid priority panics people are seeing by forcing tdq_runq_add to select the runq rather than hoping we set it properly when we adjusted the priority. This involves the same number of branches as before so should perform identically without the extra fragility. Tested by: bz Reviewed by: bz
2008-03-10 22:48:27 +00:00
ts->ts_runq = &tdq->tdq_timeshare;
Introduce two new helper macros to define the priority ranges used for interactive timeshare threads (PRI_*_INTERACTIVE) and non-interactive timeshare threads (PRI_*_BATCH) and use these instead of PRI_*_REALTIME and PRI_*_TIMESHARE. No functional change. Reviewed by: jeff
2011-01-13 14:22:27 +00:00
KASSERT(pri <= PRI_MAX_BATCH && pri >= PRI_MIN_BATCH,
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
("Invalid priority %d on timeshare runq", pri));
/*
* This queue contains only priorities between MIN and MAX
* realtime. Use the whole queue to represent these values.
*/
- Share scheduler locks between hyper-threaded cores to protect the tdq_group structure. Hyper-threaded cores won't really benefit from seperate locks anyway. - Seperate out the migration case from sched_switch to simplify the main switch code. We only migrate here if called via sched_bind(). - When preempted place the preempted thread back in the same queue at the head. - Improve the cpu group and topology infrastructure. Tested by: many on current@ Approved by: re
2007-08-03 23:38:46 +00:00
if ((flags & (SRQ_BORROWING|SRQ_PREEMPTED)) == 0) {
ule: ensure that batch timeshare threads are scheduled fairly With the previous code, if the range of priorities for timeshare batch threads was greater than RQ_NQS, then the threads with low priorities in the part of the range above RQ_NQS would be scheduled to the run-queues as if they had high priorities at the beginning of the range. In other words, threads with a nice level of +N could be scheduled as if they had a nice level of -M. Reported by: George Mitchell <george@m5p.com> Reviewed by: jhb Tested by: George Mitchell <george@m5p.com> (earlier version) MFC after: 1 week
2011-12-19 20:01:21 +00:00
pri = RQ_NQS * (pri - PRI_MIN_BATCH) / PRI_BATCH_RANGE;
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
pri = (pri + tdq->tdq_idx) % RQ_NQS;
- Only allow the tdq_idx to increase by one each tick rather than up to the most recently chosen index. This significantly improves nice behavior. This allows a lower priority thread to run some multiple of times before the higher priority thread makes it to the front of the queue. A nice +20 cpu hog now only gets ~5% of the cpu when running with a nice 0 cpu hog and about 1.5% with a nice -20 hog. A nice difference of 1 makes a 4% difference in cpu usage between two hogs. - Track a seperate insert and removal index. When the removal index is empty it is updated to point at the current insert index. - Don't remove and re-add a thread to the runq when it is being adjusted down in priority. - Pull some conditional code out of sched_tick(). It's looking a bit large now.
2007-01-04 12:16:19 +00:00
/*
* This effectively shortens the queue by one so we
* can have a one slot difference between idx and
* ridx while we wait for threads to drain.
*/
if (tdq->tdq_ridx != tdq->tdq_idx &&
pri == tdq->tdq_ridx)
- Cast the intermediate value in priority computtion back down to unsigned char. Weirdly, casting the 1 constant to u_char still produces a signed integer result that is then used in the % computation. This avoids that mess all together and causes a 0 pri to turn into 255 % 64 as we expect. Reported by: kkenn (about 4 times, thanks)
2007-03-17 18:13:32 +00:00
pri = (unsigned char)(pri - 1) % RQ_NQS;
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
} else
- Only allow the tdq_idx to increase by one each tick rather than up to the most recently chosen index. This significantly improves nice behavior. This allows a lower priority thread to run some multiple of times before the higher priority thread makes it to the front of the queue. A nice +20 cpu hog now only gets ~5% of the cpu when running with a nice 0 cpu hog and about 1.5% with a nice -20 hog. A nice difference of 1 makes a 4% difference in cpu usage between two hogs. - Track a seperate insert and removal index. When the removal index is empty it is updated to point at the current insert index. - Don't remove and re-add a thread to the runq when it is being adjusted down in priority. - Pull some conditional code out of sched_tick(). It's looking a bit large now.
2007-01-04 12:16:19 +00:00
pri = tdq->tdq_ridx;
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
runq_add_pri(ts->ts_runq, td, pri, flags);
- Fix the invalid priority panics people are seeing by forcing tdq_runq_add to select the runq rather than hoping we set it properly when we adjusted the priority. This involves the same number of branches as before so should perform identically without the extra fragility. Tested by: bz Reviewed by: bz
2008-03-10 22:48:27 +00:00
return;
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
} else
Reduce ULE context switch time by over 25%. - Only calculate timeshare priorities once per tick or when a thread is woken from sleeping. - Keep the ts_runq pointer valid after all priority changes. - Call tdq_runq_add() directly from sched_switch() without passing in via tdq_add(). We don't need to adjust loads or runqs anymore. - Sort tdq and ts_sched according to utilization to improve cache behavior. Sponsored by: Nokia
2008-03-10 03:15:19 +00:00
ts->ts_runq = &tdq->tdq_idle;
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
runq_add(ts->ts_runq, td, flags);
Reduce ULE context switch time by over 25%. - Only calculate timeshare priorities once per tick or when a thread is woken from sleeping. - Keep the ts_runq pointer valid after all priority changes. - Call tdq_runq_add() directly from sched_switch() without passing in via tdq_add(). We don't need to adjust loads or runqs anymore. - Sort tdq and ts_sched according to utilization to improve cache behavior. Sponsored by: Nokia
2008-03-10 03:15:19 +00:00
}
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* Remove a thread from a run-queue. This typically happens when a thread
* is selected to run. Running threads are not on the queue and the
* transferable count does not reflect them.
*/
- Introduce kseq_runq_{add,rem}() which are used to insert and remove kses from the run queues. Also, on SMP, we track the transferable count here. Threads are transferable only as long as they are on the run queue. - Previously, we adjusted our load balancing based on the transferable count minus the number of actual cpus. This was done to account for the threads which were likely to be running. All of this logic is simpler now that transferable accounts for only those threads which can actually be taken. Updated various places in sched_add() and kseq_balance() to account for this. - Rename kseq_{add,rem} to kseq_load_{add,rem} to reflect what they're really doing. The load is accounted for seperately from the runq because the load is accounted for even as the thread is running. - Fix a bug in sched_class() where we weren't properly using the PRI_BASE() version of the kg_pri_class. - Add a large comment that describes the impact of a seemingly simple conditional in sched_add(). - Also in sched_add() check the transferable count and KSE_CAN_MIGRATE() prior to checking kseq_idle. This reduces the frequency of access for kseq_idle which is a shared resource.
2003-11-15 07:32:07 +00:00
static __inline void
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
tdq_runq_rem(struct tdq *tdq, struct thread *td)
- Introduce kseq_runq_{add,rem}() which are used to insert and remove kses from the run queues. Also, on SMP, we track the transferable count here. Threads are transferable only as long as they are on the run queue. - Previously, we adjusted our load balancing based on the transferable count minus the number of actual cpus. This was done to account for the threads which were likely to be running. All of this logic is simpler now that transferable accounts for only those threads which can actually be taken. Updated various places in sched_add() and kseq_balance() to account for this. - Rename kseq_{add,rem} to kseq_load_{add,rem} to reflect what they're really doing. The load is accounted for seperately from the runq because the load is accounted for even as the thread is running. - Fix a bug in sched_class() where we weren't properly using the PRI_BASE() version of the kg_pri_class. - Add a large comment that describes the impact of a seemingly simple conditional in sched_add(). - Also in sched_add() check the transferable count and KSE_CAN_MIGRATE() prior to checking kseq_idle. This reduces the frequency of access for kseq_idle which is a shared resource.
2003-11-15 07:32:07 +00:00
{
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
struct td_sched *ts;
Get rid of struct proc p_sched and struct thread td_sched pointers. p_sched is unused. The struct td_sched is always co-allocated with the struct thread, except for the thread0. Avoid useless indirection, instead calculate td_sched location using simple pointer arithmetic in td_get_sched(9). For thread0, which is statically allocated, create a structure to emulate layout of the dynamic allocation. Reviewed by: jhb (previous version) Sponsored by: The FreeBSD Foundation Differential revision: https://reviews.freebsd.org/D6711
2016-06-05 17:04:03 +00:00
ts = td_get_sched(td);
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
KASSERT(ts->ts_runq != NULL,
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
("tdq_runq_remove: thread %p null ts_runq", td));
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
if (ts->ts_flags & TSF_XFERABLE) {
- Clean up a bit after the most recent KSE restructuring.
2006-12-29 10:37:07 +00:00
tdq->tdq_transferable--;
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
ts->ts_flags &= ~TSF_XFERABLE;
- Add support for CPU groups to ule. All SMT cores on the same physical cpu are added to a group. - Don't place a cpu into the kseq_idle bitmask until all cpus in that group have idled. - Prefer idle groups over idle group members in the new kseq_transfer() function. In this way we will prefer to balance load across full cores rather than add further load a partial core. - Before a cpu goes idle, check the other group members for threads. Since SMT cpus may freely share threads, this is cheap. - SMT cores may be individually pinned and bound to now. This contrasts the old mechanism where binding or pinning would have allowed a thread to run on any available cpu. - Remove some unnecessary logic from sched_switch(). Priority propagation should be properly taken care of in sched_prio() now.
2003-12-11 03:57:10 +00:00
}
- Only allow the tdq_idx to increase by one each tick rather than up to the most recently chosen index. This significantly improves nice behavior. This allows a lower priority thread to run some multiple of times before the higher priority thread makes it to the front of the queue. A nice +20 cpu hog now only gets ~5% of the cpu when running with a nice 0 cpu hog and about 1.5% with a nice -20 hog. A nice difference of 1 makes a 4% difference in cpu usage between two hogs. - Track a seperate insert and removal index. When the removal index is empty it is updated to point at the current insert index. - Don't remove and re-add a thread to the runq when it is being adjusted down in priority. - Pull some conditional code out of sched_tick(). It's looking a bit large now.
2007-01-04 12:16:19 +00:00
if (ts->ts_runq == &tdq->tdq_timeshare) {
if (tdq->tdq_idx != tdq->tdq_ridx)
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
runq_remove_idx(ts->ts_runq, td, &tdq->tdq_ridx);
- Only allow the tdq_idx to increase by one each tick rather than up to the most recently chosen index. This significantly improves nice behavior. This allows a lower priority thread to run some multiple of times before the higher priority thread makes it to the front of the queue. A nice +20 cpu hog now only gets ~5% of the cpu when running with a nice 0 cpu hog and about 1.5% with a nice -20 hog. A nice difference of 1 makes a 4% difference in cpu usage between two hogs. - Track a seperate insert and removal index. When the removal index is empty it is updated to point at the current insert index. - Don't remove and re-add a thread to the runq when it is being adjusted down in priority. - Pull some conditional code out of sched_tick(). It's looking a bit large now.
2007-01-04 12:16:19 +00:00
else
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
runq_remove_idx(ts->ts_runq, td, NULL);
- Only allow the tdq_idx to increase by one each tick rather than up to the most recently chosen index. This significantly improves nice behavior. This allows a lower priority thread to run some multiple of times before the higher priority thread makes it to the front of the queue. A nice +20 cpu hog now only gets ~5% of the cpu when running with a nice 0 cpu hog and about 1.5% with a nice -20 hog. A nice difference of 1 makes a 4% difference in cpu usage between two hogs. - Track a seperate insert and removal index. When the removal index is empty it is updated to point at the current insert index. - Don't remove and re-add a thread to the runq when it is being adjusted down in priority. - Pull some conditional code out of sched_tick(). It's looking a bit large now.
2007-01-04 12:16:19 +00:00
} else
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
runq_remove(ts->ts_runq, td);
- Introduce kseq_runq_{add,rem}() which are used to insert and remove kses from the run queues. Also, on SMP, we track the transferable count here. Threads are transferable only as long as they are on the run queue. - Previously, we adjusted our load balancing based on the transferable count minus the number of actual cpus. This was done to account for the threads which were likely to be running. All of this logic is simpler now that transferable accounts for only those threads which can actually be taken. Updated various places in sched_add() and kseq_balance() to account for this. - Rename kseq_{add,rem} to kseq_load_{add,rem} to reflect what they're really doing. The load is accounted for seperately from the runq because the load is accounted for even as the thread is running. - Fix a bug in sched_class() where we weren't properly using the PRI_BASE() version of the kg_pri_class. - Add a large comment that describes the impact of a seemingly simple conditional in sched_add(). - Also in sched_add() check the transferable count and KSE_CAN_MIGRATE() prior to checking kseq_idle. This reduces the frequency of access for kseq_idle which is a shared resource.
2003-11-15 07:32:07 +00:00
}
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* Load is maintained for all threads RUNNING and ON_RUNQ. Add the load
* for this thread to the referenced thread queue.
*/
- Add a SYSCTL node for the ule scheduler. - Allow user adjustable min and max time slices (suggested by hiten). - Change the SLP_RUN_MAX to 100ms from 2 seconds so that we learn whether a process is interactive or not much more quickly. - Place a process on the current run queue if it is interactive or if it is running at an interrupt thread priority due to priority prop. - Use the 'current' timeshare queue for interrupt threads, realtime threads, and idle threads that are running at higher priority due to priority prop. This fixes problems where priorities would have been elevated but we would not check the timeshare run queue until other lower priority tasks were no longer runnable. - Keep an array of loads indexed by the priority class as well as a global load. - Keep an bucket of nice values with a count of the number of kses currently runnable with that nice value. - Keep track of the minimum nice value of any running thread. - Remove the unused short term sleep accounting. I was attempting to use this for load balancing but it didn't work out. - Define a kseq_print() for use with debugging. - Add KTR debugging at useful places so we can easily debug slice and priority assignment. - Decouple the runq assignment from the kseq assignment. kseq_add now keeps track of statistics. This is done so that the nice and load is still tracked for the currently running process. Previously if a niced process was added while a non nice process was running the niced process would still get a slice since it was not aware of the unnice process. - Make adjustments for the sched api changes.
2003-04-11 03:47:14 +00:00
static void
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
tdq_load_add(struct tdq *tdq, struct thread *td)
- Add a SYSCTL node for the ule scheduler. - Allow user adjustable min and max time slices (suggested by hiten). - Change the SLP_RUN_MAX to 100ms from 2 seconds so that we learn whether a process is interactive or not much more quickly. - Place a process on the current run queue if it is interactive or if it is running at an interrupt thread priority due to priority prop. - Use the 'current' timeshare queue for interrupt threads, realtime threads, and idle threads that are running at higher priority due to priority prop. This fixes problems where priorities would have been elevated but we would not check the timeshare run queue until other lower priority tasks were no longer runnable. - Keep an array of loads indexed by the priority class as well as a global load. - Keep an bucket of nice values with a count of the number of kses currently runnable with that nice value. - Keep track of the minimum nice value of any running thread. - Remove the unused short term sleep accounting. I was attempting to use this for load balancing but it didn't work out. - Define a kseq_print() for use with debugging. - Add KTR debugging at useful places so we can easily debug slice and priority assignment. - Decouple the runq assignment from the kseq assignment. kseq_add now keeps track of statistics. This is done so that the nice and load is still tracked for the currently running process. Previously if a niced process was added while a non nice process was running the niced process would still get a slice since it was not aware of the unnice process. - Make adjustments for the sched api changes.
2003-04-11 03:47:14 +00:00
{
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
THREAD_LOCK_ASSERT(td, MA_OWNED);
- Don't check for the ITHD pri class in tdq_load_add and rem. 4BSD doesn't do this either. Simply check P_NOLOAD. It'd be nice if this was in a thread flag so we didn't have an extra cache miss every time we add and remove a thread from the run-queue.
2008-04-04 01:04:43 +00:00
- Clean up a bit after the most recent KSE restructuring.
2006-12-29 10:37:07 +00:00
tdq->tdq_load++;
Split P_NOLOAD into a per-thread flag (TDF_NOLOAD). This improvements aims for avoiding further cache-misses in scheduler specific functions which need to keep track of average thread running time and further locking in places setting for this flag. Reported by: jeff (originally), kris (currently) Reviewed by: jhb Tested by: Giuseppe Cocomazzi <sbudella at email dot it>
2009-11-03 16:46:52 +00:00
if ((td->td_flags & TDF_NOLOAD) == 0)
- Clean up a bit after the most recent KSE restructuring.
2006-12-29 10:37:07 +00:00
tdq->tdq_sysload++;
- Implement generic macros for producing KTR records that are compatible with src/tools/sched/schedgraph.py. This allows developers to quickly create a graphical view of ktr data for any resource in the system. - Add sched_tdname() and the pcpu field 'name' for quickly and uniformly identifying records associated with a thread or cpu. - Reimplement the KTR_SCHED traces using the new generic facility. Obtained from: attilio Discussed with: jhb Sponsored by: Nokia
2009-01-17 07:17:57 +00:00
KTR_COUNTER0(KTR_SCHED, "load", tdq->tdq_loadname, tdq->tdq_load);
dtrace sdt: remove the ugly sname parameter of SDT_PROBE_DEFINE In its stead use the Solaris / illumos approach of emulating '-' (dash) in probe names with '__' (two consecutive underscores). Reviewed by: markj MFC after: 3 weeks
2013-11-26 08:46:27 +00:00
SDT_PROBE2(sched, , , load__change, (int)TDQ_ID(tdq), tdq->tdq_load);
- Make some context switches conditional on SCHED_STRICT_RESCHED. This may have some negative effect on interactivity but it yields great perf. gains. This also brings the conditions under which ULE context switches inline with SCHED_4BSD. - Define some new kseq_* functions for manipulating the run queue. - Add a new kseq member ksq_rslices and ksq_bload. rslices is the sum of the slices of runnable kses. This will be used for push load balance decisions. bload is the number of threads blocked waiting on IO.
2003-02-03 05:30:07 +00:00
}
- Add a SYSCTL node for the ule scheduler. - Allow user adjustable min and max time slices (suggested by hiten). - Change the SLP_RUN_MAX to 100ms from 2 seconds so that we learn whether a process is interactive or not much more quickly. - Place a process on the current run queue if it is interactive or if it is running at an interrupt thread priority due to priority prop. - Use the 'current' timeshare queue for interrupt threads, realtime threads, and idle threads that are running at higher priority due to priority prop. This fixes problems where priorities would have been elevated but we would not check the timeshare run queue until other lower priority tasks were no longer runnable. - Keep an array of loads indexed by the priority class as well as a global load. - Keep an bucket of nice values with a count of the number of kses currently runnable with that nice value. - Keep track of the minimum nice value of any running thread. - Remove the unused short term sleep accounting. I was attempting to use this for load balancing but it didn't work out. - Define a kseq_print() for use with debugging. - Add KTR debugging at useful places so we can easily debug slice and priority assignment. - Decouple the runq assignment from the kseq assignment. kseq_add now keeps track of statistics. This is done so that the nice and load is still tracked for the currently running process. Previously if a niced process was added while a non nice process was running the niced process would still get a slice since it was not aware of the unnice process. - Make adjustments for the sched api changes.
2003-04-11 03:47:14 +00:00
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* Remove the load from a thread that is transitioning to a sleep state or
* exiting.
*/
- Keep seperate statistics and run queues for different scheduling classes. - Treat each class specially in kseq_{choose,add,rem}. Let the rest of the code be less aware of scheduling classes. - Skip the interactivity calculation for non TIMESHARE ksegrps. - Move slice and runq selection into kseq_add(). Uninline it now that it's big.
2003-04-03 00:29:28 +00:00
static void
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
tdq_load_rem(struct tdq *tdq, struct thread *td)
- Make some context switches conditional on SCHED_STRICT_RESCHED. This may have some negative effect on interactivity but it yields great perf. gains. This also brings the conditions under which ULE context switches inline with SCHED_4BSD. - Define some new kseq_* functions for manipulating the run queue. - Add a new kseq member ksq_rslices and ksq_bload. rslices is the sum of the slices of runnable kses. This will be used for push load balance decisions. bload is the number of threads blocked waiting on IO.
2003-02-03 05:30:07 +00:00
{
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
THREAD_LOCK_ASSERT(td, MA_OWNED);
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
KASSERT(tdq->tdq_load != 0,
- Share scheduler locks between hyper-threaded cores to protect the tdq_group structure. Hyper-threaded cores won't really benefit from seperate locks anyway. - Seperate out the migration case from sched_switch to simplify the main switch code. We only migrate here if called via sched_bind(). - When preempted place the preempted thread back in the same queue at the head. - Improve the cpu group and topology infrastructure. Tested by: many on current@ Approved by: re
2007-08-03 23:38:46 +00:00
("tdq_load_rem: Removing with 0 load on queue %d", TDQ_ID(tdq)));
- Don't check for the ITHD pri class in tdq_load_add and rem. 4BSD doesn't do this either. Simply check P_NOLOAD. It'd be nice if this was in a thread flag so we didn't have an extra cache miss every time we add and remove a thread from the run-queue.
2008-04-04 01:04:43 +00:00
- Clean up a bit after the most recent KSE restructuring.
2006-12-29 10:37:07 +00:00
tdq->tdq_load--;
Split P_NOLOAD into a per-thread flag (TDF_NOLOAD). This improvements aims for avoiding further cache-misses in scheduler specific functions which need to keep track of average thread running time and further locking in places setting for this flag. Reported by: jeff (originally), kris (currently) Reviewed by: jhb Tested by: Giuseppe Cocomazzi <sbudella at email dot it>
2009-11-03 16:46:52 +00:00
if ((td->td_flags & TDF_NOLOAD) == 0)
- Don't check for the ITHD pri class in tdq_load_add and rem. 4BSD doesn't do this either. Simply check P_NOLOAD. It'd be nice if this was in a thread flag so we didn't have an extra cache miss every time we add and remove a thread from the run-queue.
2008-04-04 01:04:43 +00:00
tdq->tdq_sysload--;
- Implement generic macros for producing KTR records that are compatible with src/tools/sched/schedgraph.py. This allows developers to quickly create a graphical view of ktr data for any resource in the system. - Add sched_tdname() and the pcpu field 'name' for quickly and uniformly identifying records associated with a thread or cpu. - Reimplement the KTR_SCHED traces using the new generic facility. Obtained from: attilio Discussed with: jhb Sponsored by: Nokia
2009-01-17 07:17:57 +00:00
KTR_COUNTER0(KTR_SCHED, "load", tdq->tdq_loadname, tdq->tdq_load);
dtrace sdt: remove the ugly sname parameter of SDT_PROBE_DEFINE In its stead use the Solaris / illumos approach of emulating '-' (dash) in probe names with '__' (two consecutive underscores). Reviewed by: markj MFC after: 3 weeks
2013-11-26 08:46:27 +00:00
SDT_PROBE2(sched, , , load__change, (int)TDQ_ID(tdq), tdq->tdq_load);
- Make some context switches conditional on SCHED_STRICT_RESCHED. This may have some negative effect on interactivity but it yields great perf. gains. This also brings the conditions under which ULE context switches inline with SCHED_4BSD. - Define some new kseq_* functions for manipulating the run queue. - Add a new kseq member ksq_rslices and ksq_bload. rslices is the sum of the slices of runnable kses. This will be used for push load balance decisions. bload is the number of threads blocked waiting on IO.
2003-02-03 05:30:07 +00:00
}
- Change ULE to use dynamic slice sizes for the timeshare queue in order to further reduce latency for threads in this queue. This should help as threads transition from realtime to timeshare. The latency is bound to a max of sched_slice until we have more than sched_slice / 6 threads runnable. Then the min slice is allotted to all threads and latency becomes (nthreads - 1) * min_slice. Discussed with: mav
2012-11-08 01:46:47 +00:00
/*
* Bound timeshare latency by decreasing slice size as load increases. We
* consider the maximum latency as the sum of the threads waiting to run
* aside from curthread and target no more than sched_slice latency but
* no less than sched_slice_min runtime.
*/
static inline int
tdq_slice(struct tdq *tdq)
{
int load;
/*
* It is safe to use sys_load here because this is called from
* contexts where timeshare threads are running and so there
* cannot be higher priority load in the system.
*/
load = tdq->tdq_sysload - 1;
if (load >= SCHED_SLICE_MIN_DIVISOR)
return (sched_slice_min);
if (load <= 1)
return (sched_slice);
return (sched_slice / load);
}
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
/*
* Set lowpri to its exact value by searching the run-queue and
* evaluating curthread. curthread may be passed as an optimization.
*/
static void
tdq_setlowpri(struct tdq *tdq, struct thread *ctd)
{
struct thread *td;
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
if (ctd == NULL)
ctd = pcpu_find(TDQ_ID(tdq))->pc_curthread;
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
td = tdq_choose(tdq);
if (td == NULL || td->td_priority > ctd->td_priority)
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
tdq->tdq_lowpri = ctd->td_priority;
else
tdq->tdq_lowpri = td->td_priority;
}
- Add a SYSCTL node for the ule scheduler. - Allow user adjustable min and max time slices (suggested by hiten). - Change the SLP_RUN_MAX to 100ms from 2 seconds so that we learn whether a process is interactive or not much more quickly. - Place a process on the current run queue if it is interactive or if it is running at an interrupt thread priority due to priority prop. - Use the 'current' timeshare queue for interrupt threads, realtime threads, and idle threads that are running at higher priority due to priority prop. This fixes problems where priorities would have been elevated but we would not check the timeshare run queue until other lower priority tasks were no longer runnable. - Keep an array of loads indexed by the priority class as well as a global load. - Keep an bucket of nice values with a count of the number of kses currently runnable with that nice value. - Keep track of the minimum nice value of any running thread. - Remove the unused short term sleep accounting. I was attempting to use this for load balancing but it didn't work out. - Define a kseq_print() for use with debugging. - Add KTR debugging at useful places so we can easily debug slice and priority assignment. - Decouple the runq assignment from the kseq assignment. kseq_add now keeps track of statistics. This is done so that the nice and load is still tracked for the currently running process. Previously if a niced process was added while a non nice process was running the niced process would still get a slice since it was not aware of the unnice process. - Make adjustments for the sched api changes.
2003-04-11 03:47:14 +00:00
#ifdef SMP
Relocate sched_random() within the SMP section. Place sched_random nearer to where it's first used: moving the code nearer to where it is used makes the code easier to read and we can reduce the initial "#ifdef SMP" island. Reword a little the comment and clean some whitespaces while here.
2015-07-07 15:22:29 +00:00
/*
* We need some randomness. Implement a classic Linear Congruential
* Generator X_{n+1}=(aX_n+c) mod m. These values are optimized for
* m = 2^32, a = 69069 and c = 5. We only return the upper 16 bits
* of the random state (in the low bits of our answer) to keep
* the maximum randomness.
*/
static uint32_t
sched_random(void)
{
uint32_t *rndptr;
rndptr = DPCPU_PTR(randomval);
*rndptr = *rndptr * 69069 + 5;
return (*rndptr >> 16);
}
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
struct cpu_search {
- Use cpuset_t and the CPU_ macros in place of cpumask_t so that ULE supports arbitrary numbers of cpus rather than being limited by cpumask_t to the number of bits in a long.
2009-06-23 22:12:37 +00:00
cpuset_t cs_mask;
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
u_int cs_prefer;
int cs_pri; /* Min priority for low. */
int cs_limit; /* Max load for low, min load for high. */
int cs_cpu;
int cs_load;
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
};
#define CPU_SEARCH_LOWEST 0x1
#define CPU_SEARCH_HIGHEST 0x2
#define CPU_SEARCH_BOTH (CPU_SEARCH_LOWEST|CPU_SEARCH_HIGHEST)
- Use cpuset_t and the CPU_ macros in place of cpumask_t so that ULE supports arbitrary numbers of cpus rather than being limited by cpumask_t to the number of bits in a long.
2009-06-23 22:12:37 +00:00
#define CPUSET_FOREACH(cpu, mask) \
for ((cpu) = 0; (cpu) <= mp_maxid; (cpu)++) \
Commit the support for removing cpumask_t and replacing it directly with cpuset_t objects. That is going to offer the underlying support for a simple bump of MAXCPU and then support for number of cpus > 32 (as it is today). Right now, cpumask_t is an int, 32 bits on all our supported architecture. cpumask_t on the other side is implemented as an array of longs, and easilly extendible by definition. The architectures touched by this commit are the following: - amd64 - i386 - pc98 - arm - ia64 - XEN while the others are still missing. Userland is believed to be fully converted with the changes contained here. Some technical notes: - This commit may be considered an ABI nop for all the architectures different from amd64 and ia64 (and sparc64 in the future) - per-cpu members, which are now converted to cpuset_t, needs to be accessed avoiding migration, because the size of cpuset_t should be considered unknown - size of cpuset_t objects is different from kernel and userland (this is primirally done in order to leave some more space in userland to cope with KBI extensions). If you need to access kernel cpuset_t from the userland please refer to example in this patch on how to do that correctly (kgdb may be a good source, for example). - Support for other architectures is going to be added soon - Only MAXCPU for amd64 is bumped now The patch has been tested by sbruno and Nicholas Esborn on opteron 4 x 12 pack CPUs. More testing on big SMP is expected to came soon. pluknet tested the patch with his 8-ways on both amd64 and i386. Tested by: pluknet, sbruno, gianni, Nicholas Esborn Reviewed by: jeff, jhb, sbruno
2011-05-05 14:39:14 +00:00
if (CPU_ISSET(cpu, &mask))
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
Micro-manage clang to get the expected inlining for cpu_search(). Mark cpu_search_lowest/cpu_search_highest/cpu_search_both as noinline, while cpu_search() gets always_inline. With the attributes set, cpu_search() is inlined in wrappers, and if()s with constant conditionals are optimized. On some tests on many-core machine, the hwpmc reported samples for cpu_search*() are reduced from 25% total to 9%. Submitted by: "Rang, Anton" <anton.rang@isilon.com> MFC after: 1 week
2014-07-03 11:06:27 +00:00
static __always_inline int cpu_search(const struct cpu_group *cg,
struct cpu_search *low, struct cpu_search *high, const int match);
int __noinline cpu_search_lowest(const struct cpu_group *cg,
struct cpu_search *low);
int __noinline cpu_search_highest(const struct cpu_group *cg,
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
struct cpu_search *high);
Micro-manage clang to get the expected inlining for cpu_search(). Mark cpu_search_lowest/cpu_search_highest/cpu_search_both as noinline, while cpu_search() gets always_inline. With the attributes set, cpu_search() is inlined in wrappers, and if()s with constant conditionals are optimized. On some tests on many-core machine, the hwpmc reported samples for cpu_search*() are reduced from 25% total to 9%. Submitted by: "Rang, Anton" <anton.rang@isilon.com> MFC after: 1 week
2014-07-03 11:06:27 +00:00
int __noinline cpu_search_both(const struct cpu_group *cg,
struct cpu_search *low, struct cpu_search *high);
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
/*
* Search the tree of cpu_groups for the lowest or highest loaded cpu
* according to the match argument. This routine actually compares the
* load on all paths through the tree and finds the least loaded cpu on
* the least loaded path, which may differ from the least loaded cpu in
"Buses" is the preferred plural of "bus" Replace archaic "busses" with modern form "buses." Intentionally excluded: * Old/random drivers I didn't recognize * Old hardware in general * Use of "busses" in code as identifiers No functional change. http://grammarist.com/spelling/buses-busses/ PR: 216099 Reported by: bltsrc at mail.ru Sponsored by: Dell EMC Isilon
2017-01-15 17:54:01 +00:00
* the system. This balances work among caches and buses.
- Add a simple CPU load balancing algorithm. This works by executing once a second and equalizing the load between the two most imbalanced CPU. This is intended to clear up long term load imbalances that would not be handled by the 'pull' method in sched_choose(). - Pull out some bits of sched_choose() into a kseq_move() function that moves an arbitrary thread from one kseq to another.
2003-06-09 00:39:09 +00:00
*
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
* This inline is instantiated in three forms below using constants for the
* match argument. It is reduced to the minimum set for each case. It is
* also recursive to the depth of the tree.
*/
Micro-manage clang to get the expected inlining for cpu_search(). Mark cpu_search_lowest/cpu_search_highest/cpu_search_both as noinline, while cpu_search() gets always_inline. With the attributes set, cpu_search() is inlined in wrappers, and if()s with constant conditionals are optimized. On some tests on many-core machine, the hwpmc reported samples for cpu_search*() are reduced from 25% total to 9%. Submitted by: "Rang, Anton" <anton.rang@isilon.com> MFC after: 1 week
2014-07-03 11:06:27 +00:00
static __always_inline int
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
cpu_search(const struct cpu_group *cg, struct cpu_search *low,
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
struct cpu_search *high, const int match)
{
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
struct cpu_search lgroup;
struct cpu_search hgroup;
cpuset_t cpumask;
struct cpu_group *child;
struct tdq *tdq;
Create sched_rand() and move the LCG code into that. Call this when we need randomness in ULE. This removes random() call from the rebalance interval code. Submitted by: Harrison Grundy Differential Revision: https://reviews.freebsd.org/D1968
2015-02-27 02:56:58 +00:00
int cpu, i, hload, lload, load, total, rnd;
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
total = 0;
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
cpumask = cg->cg_mask;
if (match & CPU_SEARCH_LOWEST) {
lload = INT_MAX;
lgroup = *low;
}
if (match & CPU_SEARCH_HIGHEST) {
Microoptimize cpu_search(). According to profiling, it makes one take 6% of CPU time on hackbench with its million of context switches per second, instead of 8% before.
2012-04-09 18:24:58 +00:00
hload = INT_MIN;
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
hgroup = *high;
}
/* Iterate through the child CPU groups and then remaining CPUs. */
Micro-optimize cpu_search(), allowing compiler to use more efficient inline ffsl() implementation, when it is available, instead of homegrown iteration. On dual-E5645 amd64 system (2x6x2 cores) under heavy I/O load that reduces time spent inside cpu_search() from 19% to 13%, while IOPS increased by 5%.
2013-09-07 15:16:30 +00:00
for (i = cg->cg_children, cpu = mp_maxid; ; ) {
Microoptimize cpu_search(). According to profiling, it makes one take 6% of CPU time on hackbench with its million of context switches per second, instead of 8% before.
2012-04-09 18:24:58 +00:00
if (i == 0) {
Micro-optimize cpu_search(), allowing compiler to use more efficient inline ffsl() implementation, when it is available, instead of homegrown iteration. On dual-E5645 amd64 system (2x6x2 cores) under heavy I/O load that reduces time spent inside cpu_search() from 19% to 13%, while IOPS increased by 5%.
2013-09-07 15:16:30 +00:00
#ifdef HAVE_INLINE_FFSL
cpu = CPU_FFS(&cpumask) - 1;
#else
Microoptimize cpu_search(). According to profiling, it makes one take 6% of CPU time on hackbench with its million of context switches per second, instead of 8% before.
2012-04-09 18:24:58 +00:00
while (cpu >= 0 && !CPU_ISSET(cpu, &cpumask))
cpu--;
Micro-optimize cpu_search(), allowing compiler to use more efficient inline ffsl() implementation, when it is available, instead of homegrown iteration. On dual-E5645 amd64 system (2x6x2 cores) under heavy I/O load that reduces time spent inside cpu_search() from 19% to 13%, while IOPS increased by 5%.
2013-09-07 15:16:30 +00:00
#endif
Microoptimize cpu_search(). According to profiling, it makes one take 6% of CPU time on hackbench with its million of context switches per second, instead of 8% before.
2012-04-09 18:24:58 +00:00
if (cpu < 0)
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
break;
child = NULL;
} else
Microoptimize cpu_search(). According to profiling, it makes one take 6% of CPU time on hackbench with its million of context switches per second, instead of 8% before.
2012-04-09 18:24:58 +00:00
child = &cg->cg_child[i - 1];
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
Microoptimize cpu_search(). According to profiling, it makes one take 6% of CPU time on hackbench with its million of context switches per second, instead of 8% before.
2012-04-09 18:24:58 +00:00
if (match & CPU_SEARCH_LOWEST)
lgroup.cs_cpu = -1;
if (match & CPU_SEARCH_HIGHEST)
hgroup.cs_cpu = -1;
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
if (child) { /* Handle child CPU group. */
CPU_NAND(&cpumask, &child->cg_mask);
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
switch (match) {
case CPU_SEARCH_LOWEST:
load = cpu_search_lowest(child, &lgroup);
break;
case CPU_SEARCH_HIGHEST:
load = cpu_search_highest(child, &hgroup);
break;
case CPU_SEARCH_BOTH:
load = cpu_search_both(child, &lgroup, &hgroup);
break;
}
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
} else { /* Handle child CPU. */
Micro-optimize cpu_search(), allowing compiler to use more efficient inline ffsl() implementation, when it is available, instead of homegrown iteration. On dual-E5645 amd64 system (2x6x2 cores) under heavy I/O load that reduces time spent inside cpu_search() from 19% to 13%, while IOPS increased by 5%.
2013-09-07 15:16:30 +00:00
CPU_CLR(cpu, &cpumask);
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
tdq = TDQ_CPU(cpu);
load = tdq->tdq_load * 256;
Make sched_random() return an unsigned number, and use uint32_t consistently. This also matches the per-cpu pointer declaration anyway. This changes the tweak we give to the load from -32..31 to be 0..31 which seems more inline with the rest of the code (- rnd and the -= 64). It should also provide the randomness we need, and may fix a signedness bug in the old code (it isn't clear that the effect was intentional as opposed to sloppy, and the right shift of a signed value is undefined to boot). This stores sched_balance() behavior when it used random(). Differential Revision: https://reviews.freebsd.org/D1981
2015-02-27 21:15:12 +00:00
rnd = sched_random() % 32;
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
if (match & CPU_SEARCH_LOWEST) {
if (cpu == low->cs_prefer)
load -= 64;
/* If that CPU is allowed and get data. */
Microoptimize cpu_search(). According to profiling, it makes one take 6% of CPU time on hackbench with its million of context switches per second, instead of 8% before.
2012-04-09 18:24:58 +00:00
if (tdq->tdq_lowpri > lgroup.cs_pri &&
tdq->tdq_load <= lgroup.cs_limit &&
CPU_ISSET(cpu, &lgroup.cs_mask)) {
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
lgroup.cs_cpu = cpu;
lgroup.cs_load = load - rnd;
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
}
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
}
if (match & CPU_SEARCH_HIGHEST)
Microoptimize cpu_search(). According to profiling, it makes one take 6% of CPU time on hackbench with its million of context switches per second, instead of 8% before.
2012-04-09 18:24:58 +00:00
if (tdq->tdq_load >= hgroup.cs_limit &&
tdq->tdq_transferable &&
CPU_ISSET(cpu, &hgroup.cs_mask)) {
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
hgroup.cs_cpu = cpu;
hgroup.cs_load = load - rnd;
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
}
}
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
total += load;
/* We have info about child item. Compare it. */
if (match & CPU_SEARCH_LOWEST) {
Microoptimize cpu_search(). According to profiling, it makes one take 6% of CPU time on hackbench with its million of context switches per second, instead of 8% before.
2012-04-09 18:24:58 +00:00
if (lgroup.cs_cpu >= 0 &&
Fix bug of r232207, when cpu_search() could prefer CPU group with best load, but with no CPU matching given limitations. It caused kernel panics in some cases when thread was bound to specific CPUs with cpuset(1).
2012-03-03 11:50:48 +00:00
(load < lload ||
(load == lload && lgroup.cs_load < low->cs_load))) {
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
lload = load;
low->cs_cpu = lgroup.cs_cpu;
low->cs_load = lgroup.cs_load;
}
}
if (match & CPU_SEARCH_HIGHEST)
Microoptimize cpu_search(). According to profiling, it makes one take 6% of CPU time on hackbench with its million of context switches per second, instead of 8% before.
2012-04-09 18:24:58 +00:00
if (hgroup.cs_cpu >= 0 &&
Fix bug of r232207, when cpu_search() could prefer CPU group with best load, but with no CPU matching given limitations. It caused kernel panics in some cases when thread was bound to specific CPUs with cpuset(1).
2012-03-03 11:50:48 +00:00
(load > hload ||
(load == hload && hgroup.cs_load > high->cs_load))) {
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
hload = load;
high->cs_cpu = hgroup.cs_cpu;
high->cs_load = hgroup.cs_load;
}
Microoptimize cpu_search(). According to profiling, it makes one take 6% of CPU time on hackbench with its million of context switches per second, instead of 8% before.
2012-04-09 18:24:58 +00:00
if (child) {
i--;
if (i == 0 && CPU_EMPTY(&cpumask))
break;
Micro-optimize cpu_search(), allowing compiler to use more efficient inline ffsl() implementation, when it is available, instead of homegrown iteration. On dual-E5645 amd64 system (2x6x2 cores) under heavy I/O load that reduces time spent inside cpu_search() from 19% to 13%, while IOPS increased by 5%.
2013-09-07 15:16:30 +00:00
}
#ifndef HAVE_INLINE_FFSL
else
Microoptimize cpu_search(). According to profiling, it makes one take 6% of CPU time on hackbench with its million of context switches per second, instead of 8% before.
2012-04-09 18:24:58 +00:00
cpu--;
Micro-optimize cpu_search(), allowing compiler to use more efficient inline ffsl() implementation, when it is available, instead of homegrown iteration. On dual-E5645 amd64 system (2x6x2 cores) under heavy I/O load that reduces time spent inside cpu_search() from 19% to 13%, while IOPS increased by 5%.
2013-09-07 15:16:30 +00:00
#endif
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
}
return (total);
}
/*
* cpu_search instantiations must pass constants to maintain the inline
* optimization.
- Add a simple CPU load balancing algorithm. This works by executing once a second and equalizing the load between the two most imbalanced CPU. This is intended to clear up long term load imbalances that would not be handled by the 'pull' method in sched_choose(). - Pull out some bits of sched_choose() into a kseq_move() function that moves an arbitrary thread from one kseq to another.
2003-06-09 00:39:09 +00:00
*/
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
int
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
cpu_search_lowest(const struct cpu_group *cg, struct cpu_search *low)
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
{
return cpu_search(cg, low, NULL, CPU_SEARCH_LOWEST);
}
int
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
cpu_search_highest(const struct cpu_group *cg, struct cpu_search *high)
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
{
return cpu_search(cg, NULL, high, CPU_SEARCH_HIGHEST);
}
int
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
cpu_search_both(const struct cpu_group *cg, struct cpu_search *low,
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
struct cpu_search *high)
{
return cpu_search(cg, low, high, CPU_SEARCH_BOTH);
}
/*
* Find the cpu with the least load via the least loaded path that has a
* lowpri greater than pri pri. A pri of -1 indicates any priority is
* acceptable.
*/
static inline int
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
sched_lowest(const struct cpu_group *cg, cpuset_t mask, int pri, int maxload,
int prefer)
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
{
struct cpu_search low;
low.cs_cpu = -1;
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
low.cs_prefer = prefer;
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
low.cs_mask = mask;
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
low.cs_pri = pri;
low.cs_limit = maxload;
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
cpu_search_lowest(cg, &low);
return low.cs_cpu;
}
/*
* Find the cpu with the highest load via the highest loaded path.
*/
static inline int
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
sched_highest(const struct cpu_group *cg, cpuset_t mask, int minload)
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
{
struct cpu_search high;
high.cs_cpu = -1;
high.cs_mask = mask;
high.cs_limit = minload;
cpu_search_highest(cg, &high);
return high.cs_cpu;
}
- Add static to local functions and data where it was missing. - Add an IPI based mechanism for migrating kses. This mechanism is broken down into several components. This is intended to reduce cache thrashing by eliminating most cases where one cpu touches another's run queues. - kseq_notify() appends a kse to a lockless singly linked list and conditionally sends an IPI to the target processor. Right now this is protected by sched_lock but at some point I'd like to get rid of the global lock. This is why I used something more complicated than a standard queue. - kseq_assign() processes our list of kses that have been assigned to us by other processors. This simply calls sched_add() for each item on the list after clearing the new KEF_ASSIGNED flag. This flag is used to indicate that we have been appeneded to the assigned queue but not added to the run queue yet. - In sched_add(), instead of adding a KSE to another processor's queue we use kse_notify() so that we don't touch their queue. Also in sched_add(), if KEF_ASSIGNED is already set return immediately. This can happen if a thread is removed and readded so that the priority is recorded properly. - In sched_rem() return immediately if KEF_ASSIGNED is set. All callers immediately readd simply to adjust priorites etc. - In sched_choose(), if we're running an IDLE task or the per cpu idle thread set our cpumask bit in 'kseq_idle' so that other processors may know that we are idle. Before this, make a single pass through the run queues of other processors so that we may find work more immediately if it is available. - In sched_runnable(), don't scan each processor's run queue, they will IPI us if they have work for us to do. - In sched_add(), if we're adding a thread that can be migrated and we have plenty of work to do, try to migrate the thread to an idle kseq. - Simplify the logic in sched_prio() and take the KEF_ASSIGNED flag into consideration. - No longer use kseq_choose() to steal threads, it can lose it's last argument. - Create a new function runq_steal() which operates like runq_choose() but skips threads based on some criteria. Currently it will not steal PRI_ITHD threads. In the future this will be used for CPU binding. - Create a kseq_steal() that checks each run queue with runq_steal(), use kseq_steal() in the places where we used kseq_choose() to steal with before.
2003-10-31 11:16:04 +00:00
static void
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
sched_balance_group(struct cpu_group *cg)
- Add a simple CPU load balancing algorithm. This works by executing once a second and equalizing the load between the two most imbalanced CPU. This is intended to clear up long term load imbalances that would not be handled by the 'pull' method in sched_choose(). - Pull out some bits of sched_choose() into a kseq_move() function that moves an arbitrary thread from one kseq to another.
2003-06-09 00:39:09 +00:00
{
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
cpuset_t hmask, lmask;
int high, low, anylow;
- Add a simple CPU load balancing algorithm. This works by executing once a second and equalizing the load between the two most imbalanced CPU. This is intended to clear up long term load imbalances that would not be handled by the 'pull' method in sched_choose(). - Pull out some bits of sched_choose() into a kseq_move() function that moves an arbitrary thread from one kseq to another.
2003-06-09 00:39:09 +00:00
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
CPU_FILL(&hmask);
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
for (;;) {
Decrease latency by not wrapping the idle loop's potentially lengthy search for a thread to steal inside a critical section. Since this allows the search to be preempted, restart the search if preemption happens since the search results found earlier may no longer be valid. Decrease the latency of starting a thread that may be assigned to this CPU during the search by polling for incoming threads during the search and switching to that thread instead of continuing the search. Test for stale search results and restart the search before going through the expense of calling tdq_lock_pair(). Retry some tests after grabbing the locks since things may have changed while waiting to get both locks. Eliminate special case handling for stealing from an SMT peer that uses 1 as the steal threshold. This can only succeed if a thread has been assigned but our SMT peer has not yet started executing it. This is quite rare and when it happens the other SMT thread is generally waiting for the same tdq lock that we hold. Basically both SMT threads are racing to grab the same spin lock. Add the kern.sched.always_steal knob from a ULE patch by jeff@. Incorporate another idea from Jeff's ULE patch. If the sched_switch() detects that the CPU is about to go idle, try to steal a thread before switching to the idle thread. Since the search for a thread to steal has to be done inside a critical section in this context, limit the impact on latency by adding the knob kern.sched.trysteal_limit to limit the topological distance of the search and don't restart the search if we detect stale results. If this search can't find an stealable thread, the idle loop can do a more complete search. Also poll for threads being assigned to this CPU during the search and switch to them instead of continuing the search. This change is responsibile for the majority of the improvement in parallel buildworld times. In sched_balance_group() change the minimum threshold from stealing a thread from 1 to 2. Poaching a newly assigned thread from a CPU that is waking up hasn't yet switched to that thread from idle is likely very rare and is likely to have the same lock race as is seen when stealing threads in the idle loop. Also use tdq_notify() to kick the destintation CPU instead of always sending an IPI. Update a stale comment, the number of transferable threads is not calculated. Reviewed by: kib (earlier version) Comments by: avg, jeff, mav MFC after: 1 month Differential Revision: https://reviews.freebsd.org/D12130
2018-02-23 00:12:51 +00:00
high = sched_highest(cg, hmask, 2);
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
/* Stop if there is no more CPU with transferrable threads. */
if (high == -1)
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
break;
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
CPU_CLR(high, &hmask);
CPU_COPY(&hmask, &lmask);
/* Stop if there is no more CPU left for low. */
if (CPU_EMPTY(&lmask))
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
break;
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
anylow = 1;
nextlow:
low = sched_lowest(cg, lmask, -1,
TDQ_CPU(high)->tdq_load - 1, high);
/* Stop if we looked well and found no less loaded CPU. */
if (anylow && low == -1)
break;
/* Go to next high if we found no less loaded CPU. */
if (low == -1)
continue;
/* Transfer thread from high to low. */
if (sched_balance_pair(TDQ_CPU(high), TDQ_CPU(low))) {
/* CPU that got thread can no longer be a donor. */
CPU_CLR(low, &hmask);
} else {
/*
* If failed, then there is no threads on high
* that can run on this low. Drop low from low
* mask and look for different one.
*/
CPU_CLR(low, &lmask);
anylow = 0;
goto nextlow;
}
- Add a simple CPU load balancing algorithm. This works by executing once a second and equalizing the load between the two most imbalanced CPU. This is intended to clear up long term load imbalances that would not be handled by the 'pull' method in sched_choose(). - Pull out some bits of sched_choose() into a kseq_move() function that moves an arbitrary thread from one kseq to another.
2003-06-09 00:39:09 +00:00
}
- Now that we have kseq groups, balance them seperately. - The new sched_balance_groups() function does intra-group balancing while sched_balance() balances the available groups. - Pick a random time between 0 ticks and hz * 2 ticks to restart each balancing process. Each balancer has its own timeout. - Pick a random place in the list of groups to start the search for lowest and highest group loads. This prevents us from prefering a group based on numeric position. - Use a nasty hack to stop us from preferring cpu 0. The problem is that softclock always runs on cpu 0, so it always has a little extra load. We ignore this load in the balancer for now. In the future softclock should run on a random cpu and these hacks can go away.
2003-12-12 07:33:51 +00:00
}
static void
Don't forget to use `void' for sched_balance(). It has no arguments.
2009-12-28 23:12:12 +00:00
sched_balance(void)
- Now that we have kseq groups, balance them seperately. - The new sched_balance_groups() function does intra-group balancing while sched_balance() balances the available groups. - Pick a random time between 0 ticks and hz * 2 ticks to restart each balancing process. Each balancer has its own timeout. - Pick a random place in the list of groups to start the search for lowest and highest group loads. This prevents us from prefering a group based on numeric position. - Use a nasty hack to stop us from preferring cpu 0. The problem is that softclock always runs on cpu 0, so it always has a little extra load. We ignore this load in the balancer for now. In the future softclock should run on a random cpu and these hacks can go away.
2003-12-12 07:33:51 +00:00
{
- Move the rebalancer back into hardclock to prevent potential softclock starvation caused by unbalanced interrupt loads. - Change the rebalancer to work on stathz ticks but retain randomization. - Simplify locking in tdq_idled() to use the tdq_lock_pair() rather than complex sequences of locks to avoid deadlock. Reported by: kris Approved by: re
2007-10-02 00:36:06 +00:00
struct tdq *tdq;
- Now that we have kseq groups, balance them seperately. - The new sched_balance_groups() function does intra-group balancing while sched_balance() balances the available groups. - Pick a random time between 0 ticks and hz * 2 ticks to restart each balancing process. Each balancer has its own timeout. - Pick a random place in the list of groups to start the search for lowest and highest group loads. This prevents us from prefering a group based on numeric position. - Use a nasty hack to stop us from preferring cpu 0. The problem is that softclock always runs on cpu 0, so it always has a little extra load. We ignore this load in the balancer for now. In the future softclock should run on a random cpu and these hacks can go away.
2003-12-12 07:33:51 +00:00
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
if (smp_started == 0 || rebalance == 0)
return;
Create sched_rand() and move the LCG code into that. Call this when we need randomness in ULE. This removes random() call from the rebalance interval code. Submitted by: Harrison Grundy Differential Revision: https://reviews.freebsd.org/D1968
2015-02-27 02:56:58 +00:00
balance_ticks = max(balance_interval / 2, 1) +
Make sched_random() return an unsigned number, and use uint32_t consistently. This also matches the per-cpu pointer declaration anyway. This changes the tweak we give to the load from -32..31 to be 0..31 which seems more inline with the rest of the code (- rnd and the -= 64). It should also provide the randomness we need, and may fix a signedness bug in the old code (it isn't clear that the effect was intentional as opposed to sloppy, and the right shift of a signed value is undefined to boot). This stores sched_balance() behavior when it used random(). Differential Revision: https://reviews.freebsd.org/D1981
2015-02-27 21:15:12 +00:00
(sched_random() % balance_interval);
- Move the rebalancer back into hardclock to prevent potential softclock starvation caused by unbalanced interrupt loads. - Change the rebalancer to work on stathz ticks but retain randomization. - Simplify locking in tdq_idled() to use the tdq_lock_pair() rather than complex sequences of locks to avoid deadlock. Reported by: kris Approved by: re
2007-10-02 00:36:06 +00:00
tdq = TDQ_SELF();
TDQ_UNLOCK(tdq);
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
sched_balance_group(cpu_top);
- Move the rebalancer back into hardclock to prevent potential softclock starvation caused by unbalanced interrupt loads. - Change the rebalancer to work on stathz ticks but retain randomization. - Simplify locking in tdq_idled() to use the tdq_lock_pair() rather than complex sequences of locks to avoid deadlock. Reported by: kris Approved by: re
2007-10-02 00:36:06 +00:00
TDQ_LOCK(tdq);
- Now that we have kseq groups, balance them seperately. - The new sched_balance_groups() function does intra-group balancing while sched_balance() balances the available groups. - Pick a random time between 0 ticks and hz * 2 ticks to restart each balancing process. Each balancer has its own timeout. - Pick a random place in the list of groups to start the search for lowest and highest group loads. This prevents us from prefering a group based on numeric position. - Use a nasty hack to stop us from preferring cpu 0. The problem is that softclock always runs on cpu 0, so it always has a little extra load. We ignore this load in the balancer for now. In the future softclock should run on a random cpu and these hacks can go away.
2003-12-12 07:33:51 +00:00
}
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* Lock two thread queues using their address to maintain lock order.
*/
static void
tdq_lock_pair(struct tdq *one, struct tdq *two)
{
if (one < two) {
TDQ_LOCK(one);
TDQ_LOCK_FLAGS(two, MTX_DUPOK);
} else {
TDQ_LOCK(two);
TDQ_LOCK_FLAGS(one, MTX_DUPOK);
}
}
- Move the rebalancer back into hardclock to prevent potential softclock starvation caused by unbalanced interrupt loads. - Change the rebalancer to work on stathz ticks but retain randomization. - Simplify locking in tdq_idled() to use the tdq_lock_pair() rather than complex sequences of locks to avoid deadlock. Reported by: kris Approved by: re
2007-10-02 00:36:06 +00:00
/*
* Unlock two thread queues. Order is not important here.
*/
static void
tdq_unlock_pair(struct tdq *one, struct tdq *two)
{
TDQ_UNLOCK(one);
TDQ_UNLOCK(two);
}
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* Transfer load between two imbalanced thread queues.
*/
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
static int
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
sched_balance_pair(struct tdq *high, struct tdq *low)
- Now that we have kseq groups, balance them seperately. - The new sched_balance_groups() function does intra-group balancing while sched_balance() balances the available groups. - Pick a random time between 0 ticks and hz * 2 ticks to restart each balancing process. Each balancer has its own timeout. - Pick a random place in the list of groups to start the search for lowest and highest group loads. This prevents us from prefering a group based on numeric position. - Use a nasty hack to stop us from preferring cpu 0. The problem is that softclock always runs on cpu 0, so it always has a little extra load. We ignore this load in the balancer for now. In the future softclock should run on a random cpu and these hacks can go away.
2003-12-12 07:33:51 +00:00
{
Decrease latency by not wrapping the idle loop's potentially lengthy search for a thread to steal inside a critical section. Since this allows the search to be preempted, restart the search if preemption happens since the search results found earlier may no longer be valid. Decrease the latency of starting a thread that may be assigned to this CPU during the search by polling for incoming threads during the search and switching to that thread instead of continuing the search. Test for stale search results and restart the search before going through the expense of calling tdq_lock_pair(). Retry some tests after grabbing the locks since things may have changed while waiting to get both locks. Eliminate special case handling for stealing from an SMT peer that uses 1 as the steal threshold. This can only succeed if a thread has been assigned but our SMT peer has not yet started executing it. This is quite rare and when it happens the other SMT thread is generally waiting for the same tdq lock that we hold. Basically both SMT threads are racing to grab the same spin lock. Add the kern.sched.always_steal knob from a ULE patch by jeff@. Incorporate another idea from Jeff's ULE patch. If the sched_switch() detects that the CPU is about to go idle, try to steal a thread before switching to the idle thread. Since the search for a thread to steal has to be done inside a critical section in this context, limit the impact on latency by adding the knob kern.sched.trysteal_limit to limit the topological distance of the search and don't restart the search if we detect stale results. If this search can't find an stealable thread, the idle loop can do a more complete search. Also poll for threads being assigned to this CPU during the search and switch to them instead of continuing the search. This change is responsibile for the majority of the improvement in parallel buildworld times. In sched_balance_group() change the minimum threshold from stealing a thread from 1 to 2. Poaching a newly assigned thread from a CPU that is waking up hasn't yet switched to that thread from idle is likely very rare and is likely to have the same lock race as is seen when stealing threads in the idle loop. Also use tdq_notify() to kick the destintation CPU instead of always sending an IPI. Update a stale comment, the number of transferable threads is not calculated. Reviewed by: kib (earlier version) Comments by: avg, jeff, mav MFC after: 1 month Differential Revision: https://reviews.freebsd.org/D12130
2018-02-23 00:12:51 +00:00
struct thread *td;
- Currently, sched_balance_pair() may cause a CPU to send an IPI_PREEMPT to itself, which sparc64 hardware doesn't support. One way to solve this would be to directly call sched_preempt() instead of issuing a self-IPI. However, quoting jhb@: "On the other hand, you can probably just skip the IPI entirely if we are going to send it to the current CPU. Presumably, once this routine finishes, the current CPU will exit softlock (or will do so "soon") and will then pick the next thread to run based on the adjustments made in this routine, so there's no need to IPI the CPU running this routine anyway. I think this is the better solution. Right now what is probably happening on other platforms is as soon as this routine finishes the CPU processes its self-IPI and causes mi_switch() which will just switch back to the softclock thread it is already running." - With r226054 and the the above change in place, sparc64 now no longer is incompatible with ULE and vice versa. However, powerpc/E500 still is. Submitted by: jhb Reviewed by: jeff
2011-10-06 11:48:13 +00:00
int cpu;
- Now that we have kseq groups, balance them seperately. - The new sched_balance_groups() function does intra-group balancing while sched_balance() balances the available groups. - Pick a random time between 0 ticks and hz * 2 ticks to restart each balancing process. Each balancer has its own timeout. - Pick a random place in the list of groups to start the search for lowest and highest group loads. This prevents us from prefering a group based on numeric position. - Use a nasty hack to stop us from preferring cpu 0. The problem is that softclock always runs on cpu 0, so it always has a little extra load. We ignore this load in the balancer for now. In the future softclock should run on a random cpu and these hacks can go away.
2003-12-12 07:33:51 +00:00
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
tdq_lock_pair(high, low);
Decrease latency by not wrapping the idle loop's potentially lengthy search for a thread to steal inside a critical section. Since this allows the search to be preempted, restart the search if preemption happens since the search results found earlier may no longer be valid. Decrease the latency of starting a thread that may be assigned to this CPU during the search by polling for incoming threads during the search and switching to that thread instead of continuing the search. Test for stale search results and restart the search before going through the expense of calling tdq_lock_pair(). Retry some tests after grabbing the locks since things may have changed while waiting to get both locks. Eliminate special case handling for stealing from an SMT peer that uses 1 as the steal threshold. This can only succeed if a thread has been assigned but our SMT peer has not yet started executing it. This is quite rare and when it happens the other SMT thread is generally waiting for the same tdq lock that we hold. Basically both SMT threads are racing to grab the same spin lock. Add the kern.sched.always_steal knob from a ULE patch by jeff@. Incorporate another idea from Jeff's ULE patch. If the sched_switch() detects that the CPU is about to go idle, try to steal a thread before switching to the idle thread. Since the search for a thread to steal has to be done inside a critical section in this context, limit the impact on latency by adding the knob kern.sched.trysteal_limit to limit the topological distance of the search and don't restart the search if we detect stale results. If this search can't find an stealable thread, the idle loop can do a more complete search. Also poll for threads being assigned to this CPU during the search and switch to them instead of continuing the search. This change is responsibile for the majority of the improvement in parallel buildworld times. In sched_balance_group() change the minimum threshold from stealing a thread from 1 to 2. Poaching a newly assigned thread from a CPU that is waking up hasn't yet switched to that thread from idle is likely very rare and is likely to have the same lock race as is seen when stealing threads in the idle loop. Also use tdq_notify() to kick the destintation CPU instead of always sending an IPI. Update a stale comment, the number of transferable threads is not calculated. Reviewed by: kib (earlier version) Comments by: avg, jeff, mav MFC after: 1 month Differential Revision: https://reviews.freebsd.org/D12130
2018-02-23 00:12:51 +00:00
td = NULL;
- Introduce kseq_runq_{add,rem}() which are used to insert and remove kses from the run queues. Also, on SMP, we track the transferable count here. Threads are transferable only as long as they are on the run queue. - Previously, we adjusted our load balancing based on the transferable count minus the number of actual cpus. This was done to account for the threads which were likely to be running. All of this logic is simpler now that transferable accounts for only those threads which can actually be taken. Updated various places in sched_add() and kseq_balance() to account for this. - Rename kseq_{add,rem} to kseq_load_{add,rem} to reflect what they're really doing. The load is accounted for seperately from the runq because the load is accounted for even as the thread is running. - Fix a bug in sched_class() where we weren't properly using the PRI_BASE() version of the kg_pri_class. - Add a large comment that describes the impact of a seemingly simple conditional in sched_add(). - Also in sched_add() check the transferable count and KSE_CAN_MIGRATE() prior to checking kseq_idle. This reduces the frequency of access for kseq_idle which is a shared resource.
2003-11-15 07:32:07 +00:00
/*
Decrease latency by not wrapping the idle loop's potentially lengthy search for a thread to steal inside a critical section. Since this allows the search to be preempted, restart the search if preemption happens since the search results found earlier may no longer be valid. Decrease the latency of starting a thread that may be assigned to this CPU during the search by polling for incoming threads during the search and switching to that thread instead of continuing the search. Test for stale search results and restart the search before going through the expense of calling tdq_lock_pair(). Retry some tests after grabbing the locks since things may have changed while waiting to get both locks. Eliminate special case handling for stealing from an SMT peer that uses 1 as the steal threshold. This can only succeed if a thread has been assigned but our SMT peer has not yet started executing it. This is quite rare and when it happens the other SMT thread is generally waiting for the same tdq lock that we hold. Basically both SMT threads are racing to grab the same spin lock. Add the kern.sched.always_steal knob from a ULE patch by jeff@. Incorporate another idea from Jeff's ULE patch. If the sched_switch() detects that the CPU is about to go idle, try to steal a thread before switching to the idle thread. Since the search for a thread to steal has to be done inside a critical section in this context, limit the impact on latency by adding the knob kern.sched.trysteal_limit to limit the topological distance of the search and don't restart the search if we detect stale results. If this search can't find an stealable thread, the idle loop can do a more complete search. Also poll for threads being assigned to this CPU during the search and switch to them instead of continuing the search. This change is responsibile for the majority of the improvement in parallel buildworld times. In sched_balance_group() change the minimum threshold from stealing a thread from 1 to 2. Poaching a newly assigned thread from a CPU that is waking up hasn't yet switched to that thread from idle is likely very rare and is likely to have the same lock race as is seen when stealing threads in the idle loop. Also use tdq_notify() to kick the destintation CPU instead of always sending an IPI. Update a stale comment, the number of transferable threads is not calculated. Reviewed by: kib (earlier version) Comments by: avg, jeff, mav MFC after: 1 month Differential Revision: https://reviews.freebsd.org/D12130
2018-02-23 00:12:51 +00:00
* Transfer a thread from high to low.
- Introduce kseq_runq_{add,rem}() which are used to insert and remove kses from the run queues. Also, on SMP, we track the transferable count here. Threads are transferable only as long as they are on the run queue. - Previously, we adjusted our load balancing based on the transferable count minus the number of actual cpus. This was done to account for the threads which were likely to be running. All of this logic is simpler now that transferable accounts for only those threads which can actually be taken. Updated various places in sched_add() and kseq_balance() to account for this. - Rename kseq_{add,rem} to kseq_load_{add,rem} to reflect what they're really doing. The load is accounted for seperately from the runq because the load is accounted for even as the thread is running. - Fix a bug in sched_class() where we weren't properly using the PRI_BASE() version of the kg_pri_class. - Add a large comment that describes the impact of a seemingly simple conditional in sched_add(). - Also in sched_add() check the transferable count and KSE_CAN_MIGRATE() prior to checking kseq_idle. This reduces the frequency of access for kseq_idle which is a shared resource.
2003-11-15 07:32:07 +00:00
*/
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
if (high->tdq_transferable != 0 && high->tdq_load > low->tdq_load &&
Decrease latency by not wrapping the idle loop's potentially lengthy search for a thread to steal inside a critical section. Since this allows the search to be preempted, restart the search if preemption happens since the search results found earlier may no longer be valid. Decrease the latency of starting a thread that may be assigned to this CPU during the search by polling for incoming threads during the search and switching to that thread instead of continuing the search. Test for stale search results and restart the search before going through the expense of calling tdq_lock_pair(). Retry some tests after grabbing the locks since things may have changed while waiting to get both locks. Eliminate special case handling for stealing from an SMT peer that uses 1 as the steal threshold. This can only succeed if a thread has been assigned but our SMT peer has not yet started executing it. This is quite rare and when it happens the other SMT thread is generally waiting for the same tdq lock that we hold. Basically both SMT threads are racing to grab the same spin lock. Add the kern.sched.always_steal knob from a ULE patch by jeff@. Incorporate another idea from Jeff's ULE patch. If the sched_switch() detects that the CPU is about to go idle, try to steal a thread before switching to the idle thread. Since the search for a thread to steal has to be done inside a critical section in this context, limit the impact on latency by adding the knob kern.sched.trysteal_limit to limit the topological distance of the search and don't restart the search if we detect stale results. If this search can't find an stealable thread, the idle loop can do a more complete search. Also poll for threads being assigned to this CPU during the search and switch to them instead of continuing the search. This change is responsibile for the majority of the improvement in parallel buildworld times. In sched_balance_group() change the minimum threshold from stealing a thread from 1 to 2. Poaching a newly assigned thread from a CPU that is waking up hasn't yet switched to that thread from idle is likely very rare and is likely to have the same lock race as is seen when stealing threads in the idle loop. Also use tdq_notify() to kick the destintation CPU instead of always sending an IPI. Update a stale comment, the number of transferable threads is not calculated. Reviewed by: kib (earlier version) Comments by: avg, jeff, mav MFC after: 1 month Differential Revision: https://reviews.freebsd.org/D12130
2018-02-23 00:12:51 +00:00
(td = tdq_move(high, low)) != NULL) {
- Improve grammar. s/it's/its/. - Improve load long-term load balancer by always IPIing exactly once. Previously the delay after rebalancing could cause problems with uneven workloads. - Allow nice to have a linear effect on the interactivity score. This allows negatively niced programs to stay interactive longer. It may be useful with very expensive Xorg servers under high loads. In general it should not be necessary to alter the nice level to improve interactive response. We may also want to consider never allowing positively niced processes to become interactive at all. - Initialize ccpu to 0 rather than 0.0. The decimal point was leftover from when the code was copied from 4bsd. ccpu is 0 in ULE because ULE only exports weighted cpu values. Reported by: Steve Kargl (Load balancing problem) Approved by: re
2007-09-22 02:20:14 +00:00
/*
Decrease latency by not wrapping the idle loop's potentially lengthy search for a thread to steal inside a critical section. Since this allows the search to be preempted, restart the search if preemption happens since the search results found earlier may no longer be valid. Decrease the latency of starting a thread that may be assigned to this CPU during the search by polling for incoming threads during the search and switching to that thread instead of continuing the search. Test for stale search results and restart the search before going through the expense of calling tdq_lock_pair(). Retry some tests after grabbing the locks since things may have changed while waiting to get both locks. Eliminate special case handling for stealing from an SMT peer that uses 1 as the steal threshold. This can only succeed if a thread has been assigned but our SMT peer has not yet started executing it. This is quite rare and when it happens the other SMT thread is generally waiting for the same tdq lock that we hold. Basically both SMT threads are racing to grab the same spin lock. Add the kern.sched.always_steal knob from a ULE patch by jeff@. Incorporate another idea from Jeff's ULE patch. If the sched_switch() detects that the CPU is about to go idle, try to steal a thread before switching to the idle thread. Since the search for a thread to steal has to be done inside a critical section in this context, limit the impact on latency by adding the knob kern.sched.trysteal_limit to limit the topological distance of the search and don't restart the search if we detect stale results. If this search can't find an stealable thread, the idle loop can do a more complete search. Also poll for threads being assigned to this CPU during the search and switch to them instead of continuing the search. This change is responsibile for the majority of the improvement in parallel buildworld times. In sched_balance_group() change the minimum threshold from stealing a thread from 1 to 2. Poaching a newly assigned thread from a CPU that is waking up hasn't yet switched to that thread from idle is likely very rare and is likely to have the same lock race as is seen when stealing threads in the idle loop. Also use tdq_notify() to kick the destintation CPU instead of always sending an IPI. Update a stale comment, the number of transferable threads is not calculated. Reviewed by: kib (earlier version) Comments by: avg, jeff, mav MFC after: 1 month Differential Revision: https://reviews.freebsd.org/D12130
2018-02-23 00:12:51 +00:00
* In case the target isn't the current cpu notify it of the
* new load, possibly sending an IPI to force it to reschedule.
- Improve grammar. s/it's/its/. - Improve load long-term load balancer by always IPIing exactly once. Previously the delay after rebalancing could cause problems with uneven workloads. - Allow nice to have a linear effect on the interactivity score. This allows negatively niced programs to stay interactive longer. It may be useful with very expensive Xorg servers under high loads. In general it should not be necessary to alter the nice level to improve interactive response. We may also want to consider never allowing positively niced processes to become interactive at all. - Initialize ccpu to 0 rather than 0.0. The decimal point was leftover from when the code was copied from 4bsd. ccpu is 0 in ULE because ULE only exports weighted cpu values. Reported by: Steve Kargl (Load balancing problem) Approved by: re
2007-09-22 02:20:14 +00:00
*/
- Currently, sched_balance_pair() may cause a CPU to send an IPI_PREEMPT to itself, which sparc64 hardware doesn't support. One way to solve this would be to directly call sched_preempt() instead of issuing a self-IPI. However, quoting jhb@: "On the other hand, you can probably just skip the IPI entirely if we are going to send it to the current CPU. Presumably, once this routine finishes, the current CPU will exit softlock (or will do so "soon") and will then pick the next thread to run based on the adjustments made in this routine, so there's no need to IPI the CPU running this routine anyway. I think this is the better solution. Right now what is probably happening on other platforms is as soon as this routine finishes the CPU processes its self-IPI and causes mi_switch() which will just switch back to the softclock thread it is already running." - With r226054 and the the above change in place, sparc64 now no longer is incompatible with ULE and vice versa. However, powerpc/E500 still is. Submitted by: jhb Reviewed by: jeff
2011-10-06 11:48:13 +00:00
cpu = TDQ_ID(low);
if (cpu != PCPU_GET(cpuid))
Decrease latency by not wrapping the idle loop's potentially lengthy search for a thread to steal inside a critical section. Since this allows the search to be preempted, restart the search if preemption happens since the search results found earlier may no longer be valid. Decrease the latency of starting a thread that may be assigned to this CPU during the search by polling for incoming threads during the search and switching to that thread instead of continuing the search. Test for stale search results and restart the search before going through the expense of calling tdq_lock_pair(). Retry some tests after grabbing the locks since things may have changed while waiting to get both locks. Eliminate special case handling for stealing from an SMT peer that uses 1 as the steal threshold. This can only succeed if a thread has been assigned but our SMT peer has not yet started executing it. This is quite rare and when it happens the other SMT thread is generally waiting for the same tdq lock that we hold. Basically both SMT threads are racing to grab the same spin lock. Add the kern.sched.always_steal knob from a ULE patch by jeff@. Incorporate another idea from Jeff's ULE patch. If the sched_switch() detects that the CPU is about to go idle, try to steal a thread before switching to the idle thread. Since the search for a thread to steal has to be done inside a critical section in this context, limit the impact on latency by adding the knob kern.sched.trysteal_limit to limit the topological distance of the search and don't restart the search if we detect stale results. If this search can't find an stealable thread, the idle loop can do a more complete search. Also poll for threads being assigned to this CPU during the search and switch to them instead of continuing the search. This change is responsibile for the majority of the improvement in parallel buildworld times. In sched_balance_group() change the minimum threshold from stealing a thread from 1 to 2. Poaching a newly assigned thread from a CPU that is waking up hasn't yet switched to that thread from idle is likely very rare and is likely to have the same lock race as is seen when stealing threads in the idle loop. Also use tdq_notify() to kick the destintation CPU instead of always sending an IPI. Update a stale comment, the number of transferable threads is not calculated. Reviewed by: kib (earlier version) Comments by: avg, jeff, mav MFC after: 1 month Differential Revision: https://reviews.freebsd.org/D12130
2018-02-23 00:12:51 +00:00
tdq_notify(low, td);
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
}
- Move the rebalancer back into hardclock to prevent potential softclock starvation caused by unbalanced interrupt loads. - Change the rebalancer to work on stathz ticks but retain randomization. - Simplify locking in tdq_idled() to use the tdq_lock_pair() rather than complex sequences of locks to avoid deadlock. Reported by: kris Approved by: re
2007-10-02 00:36:06 +00:00
tdq_unlock_pair(high, low);
Decrease latency by not wrapping the idle loop's potentially lengthy search for a thread to steal inside a critical section. Since this allows the search to be preempted, restart the search if preemption happens since the search results found earlier may no longer be valid. Decrease the latency of starting a thread that may be assigned to this CPU during the search by polling for incoming threads during the search and switching to that thread instead of continuing the search. Test for stale search results and restart the search before going through the expense of calling tdq_lock_pair(). Retry some tests after grabbing the locks since things may have changed while waiting to get both locks. Eliminate special case handling for stealing from an SMT peer that uses 1 as the steal threshold. This can only succeed if a thread has been assigned but our SMT peer has not yet started executing it. This is quite rare and when it happens the other SMT thread is generally waiting for the same tdq lock that we hold. Basically both SMT threads are racing to grab the same spin lock. Add the kern.sched.always_steal knob from a ULE patch by jeff@. Incorporate another idea from Jeff's ULE patch. If the sched_switch() detects that the CPU is about to go idle, try to steal a thread before switching to the idle thread. Since the search for a thread to steal has to be done inside a critical section in this context, limit the impact on latency by adding the knob kern.sched.trysteal_limit to limit the topological distance of the search and don't restart the search if we detect stale results. If this search can't find an stealable thread, the idle loop can do a more complete search. Also poll for threads being assigned to this CPU during the search and switch to them instead of continuing the search. This change is responsibile for the majority of the improvement in parallel buildworld times. In sched_balance_group() change the minimum threshold from stealing a thread from 1 to 2. Poaching a newly assigned thread from a CPU that is waking up hasn't yet switched to that thread from idle is likely very rare and is likely to have the same lock race as is seen when stealing threads in the idle loop. Also use tdq_notify() to kick the destintation CPU instead of always sending an IPI. Update a stale comment, the number of transferable threads is not calculated. Reviewed by: kib (earlier version) Comments by: avg, jeff, mav MFC after: 1 month Differential Revision: https://reviews.freebsd.org/D12130
2018-02-23 00:12:51 +00:00
return (td != NULL);
- Add a simple CPU load balancing algorithm. This works by executing once a second and equalizing the load between the two most imbalanced CPU. This is intended to clear up long term load imbalances that would not be handled by the 'pull' method in sched_choose(). - Pull out some bits of sched_choose() into a kseq_move() function that moves an arbitrary thread from one kseq to another.
2003-06-09 00:39:09 +00:00
}
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* Move a thread from one thread queue to another.
*/
Decrease latency by not wrapping the idle loop's potentially lengthy search for a thread to steal inside a critical section. Since this allows the search to be preempted, restart the search if preemption happens since the search results found earlier may no longer be valid. Decrease the latency of starting a thread that may be assigned to this CPU during the search by polling for incoming threads during the search and switching to that thread instead of continuing the search. Test for stale search results and restart the search before going through the expense of calling tdq_lock_pair(). Retry some tests after grabbing the locks since things may have changed while waiting to get both locks. Eliminate special case handling for stealing from an SMT peer that uses 1 as the steal threshold. This can only succeed if a thread has been assigned but our SMT peer has not yet started executing it. This is quite rare and when it happens the other SMT thread is generally waiting for the same tdq lock that we hold. Basically both SMT threads are racing to grab the same spin lock. Add the kern.sched.always_steal knob from a ULE patch by jeff@. Incorporate another idea from Jeff's ULE patch. If the sched_switch() detects that the CPU is about to go idle, try to steal a thread before switching to the idle thread. Since the search for a thread to steal has to be done inside a critical section in this context, limit the impact on latency by adding the knob kern.sched.trysteal_limit to limit the topological distance of the search and don't restart the search if we detect stale results. If this search can't find an stealable thread, the idle loop can do a more complete search. Also poll for threads being assigned to this CPU during the search and switch to them instead of continuing the search. This change is responsibile for the majority of the improvement in parallel buildworld times. In sched_balance_group() change the minimum threshold from stealing a thread from 1 to 2. Poaching a newly assigned thread from a CPU that is waking up hasn't yet switched to that thread from idle is likely very rare and is likely to have the same lock race as is seen when stealing threads in the idle loop. Also use tdq_notify() to kick the destintation CPU instead of always sending an IPI. Update a stale comment, the number of transferable threads is not calculated. Reviewed by: kib (earlier version) Comments by: avg, jeff, mav MFC after: 1 month Differential Revision: https://reviews.freebsd.org/D12130
2018-02-23 00:12:51 +00:00
static struct thread *
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
tdq_move(struct tdq *from, struct tdq *to)
- Add a simple CPU load balancing algorithm. This works by executing once a second and equalizing the load between the two most imbalanced CPU. This is intended to clear up long term load imbalances that would not be handled by the 'pull' method in sched_choose(). - Pull out some bits of sched_choose() into a kseq_move() function that moves an arbitrary thread from one kseq to another.
2003-06-09 00:39:09 +00:00
{
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
struct td_sched *ts;
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
struct thread *td;
struct tdq *tdq;
int cpu;
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
- Move the rebalancer back into hardclock to prevent potential softclock starvation caused by unbalanced interrupt loads. - Change the rebalancer to work on stathz ticks but retain randomization. - Simplify locking in tdq_idled() to use the tdq_lock_pair() rather than complex sequences of locks to avoid deadlock. Reported by: kris Approved by: re
2007-10-02 00:36:06 +00:00
TDQ_LOCK_ASSERT(from, MA_OWNED);
TDQ_LOCK_ASSERT(to, MA_OWNED);
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
tdq = from;
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
cpu = TDQ_ID(to);
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
td = tdq_steal(tdq, cpu);
if (td == NULL)
Decrease latency by not wrapping the idle loop's potentially lengthy search for a thread to steal inside a critical section. Since this allows the search to be preempted, restart the search if preemption happens since the search results found earlier may no longer be valid. Decrease the latency of starting a thread that may be assigned to this CPU during the search by polling for incoming threads during the search and switching to that thread instead of continuing the search. Test for stale search results and restart the search before going through the expense of calling tdq_lock_pair(). Retry some tests after grabbing the locks since things may have changed while waiting to get both locks. Eliminate special case handling for stealing from an SMT peer that uses 1 as the steal threshold. This can only succeed if a thread has been assigned but our SMT peer has not yet started executing it. This is quite rare and when it happens the other SMT thread is generally waiting for the same tdq lock that we hold. Basically both SMT threads are racing to grab the same spin lock. Add the kern.sched.always_steal knob from a ULE patch by jeff@. Incorporate another idea from Jeff's ULE patch. If the sched_switch() detects that the CPU is about to go idle, try to steal a thread before switching to the idle thread. Since the search for a thread to steal has to be done inside a critical section in this context, limit the impact on latency by adding the knob kern.sched.trysteal_limit to limit the topological distance of the search and don't restart the search if we detect stale results. If this search can't find an stealable thread, the idle loop can do a more complete search. Also poll for threads being assigned to this CPU during the search and switch to them instead of continuing the search. This change is responsibile for the majority of the improvement in parallel buildworld times. In sched_balance_group() change the minimum threshold from stealing a thread from 1 to 2. Poaching a newly assigned thread from a CPU that is waking up hasn't yet switched to that thread from idle is likely very rare and is likely to have the same lock race as is seen when stealing threads in the idle loop. Also use tdq_notify() to kick the destintation CPU instead of always sending an IPI. Update a stale comment, the number of transferable threads is not calculated. Reviewed by: kib (earlier version) Comments by: avg, jeff, mav MFC after: 1 month Differential Revision: https://reviews.freebsd.org/D12130
2018-02-23 00:12:51 +00:00
return (NULL);
Get rid of struct proc p_sched and struct thread td_sched pointers. p_sched is unused. The struct td_sched is always co-allocated with the struct thread, except for the thread0. Avoid useless indirection, instead calculate td_sched location using simple pointer arithmetic in td_get_sched(9). For thread0, which is statically allocated, create a structure to emulate layout of the dynamic allocation. Reviewed by: jhb (previous version) Sponsored by: The FreeBSD Foundation Differential revision: https://reviews.freebsd.org/D6711
2016-06-05 17:04:03 +00:00
ts = td_get_sched(td);
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* Although the run queue is locked the thread may be blocked. Lock
- Move the rebalancer back into hardclock to prevent potential softclock starvation caused by unbalanced interrupt loads. - Change the rebalancer to work on stathz ticks but retain randomization. - Simplify locking in tdq_idled() to use the tdq_lock_pair() rather than complex sequences of locks to avoid deadlock. Reported by: kris Approved by: re
2007-10-02 00:36:06 +00:00
* it to clear this and acquire the run-queue lock.
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
*/
thread_lock(td);
- Move the rebalancer back into hardclock to prevent potential softclock starvation caused by unbalanced interrupt loads. - Change the rebalancer to work on stathz ticks but retain randomization. - Simplify locking in tdq_idled() to use the tdq_lock_pair() rather than complex sequences of locks to avoid deadlock. Reported by: kris Approved by: re
2007-10-02 00:36:06 +00:00
/* Drop recursive lock on from acquired via thread_lock(). */
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
TDQ_UNLOCK(from);
sched_rem(td);
Major revamp of ULE's cpu load balancing: - Switch back to direct modification of remote CPU run queues. This added a lot of complexity with questionable gain. It's easy enough to reimplement if it's shown to help on huge machines. - Re-implement the old tdq_transfer() call as tdq_pickidle(). Change sched_add() so we have selectable cpu choosers and simplify the logic a bit here. - Implement tdq_pickpri() as the new default cpu chooser. This algorithm is similar to Solaris in that it tries to always run the threads with the best priorities. It is actually slightly more complex than solaris's algorithm because we also tend to favor the local cpu over other cpus which has a boost in latency but also potentially enables cache sharing between the waking thread and the woken thread. - Add a bunch of tunables that can be used to measure effects of different load balancing strategies. Most of these will go away once the algorithm is more definite. - Add a new mechanism to steal threads from busy cpus when we idle. This is enabled with kern.sched.steal_busy and kern.sched.busy_thresh. The threshold is the required length of a tdq's run queue before another cpu will be able to steal runnable threads. This prevents most queue imbalances that contribute the long latencies.
2007-01-19 21:56:08 +00:00
ts->ts_cpu = cpu;
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
td->td_lock = TDQ_LOCKPTR(to);
tdq_add(to, td, SRQ_YIELDING);
Decrease latency by not wrapping the idle loop's potentially lengthy search for a thread to steal inside a critical section. Since this allows the search to be preempted, restart the search if preemption happens since the search results found earlier may no longer be valid. Decrease the latency of starting a thread that may be assigned to this CPU during the search by polling for incoming threads during the search and switching to that thread instead of continuing the search. Test for stale search results and restart the search before going through the expense of calling tdq_lock_pair(). Retry some tests after grabbing the locks since things may have changed while waiting to get both locks. Eliminate special case handling for stealing from an SMT peer that uses 1 as the steal threshold. This can only succeed if a thread has been assigned but our SMT peer has not yet started executing it. This is quite rare and when it happens the other SMT thread is generally waiting for the same tdq lock that we hold. Basically both SMT threads are racing to grab the same spin lock. Add the kern.sched.always_steal knob from a ULE patch by jeff@. Incorporate another idea from Jeff's ULE patch. If the sched_switch() detects that the CPU is about to go idle, try to steal a thread before switching to the idle thread. Since the search for a thread to steal has to be done inside a critical section in this context, limit the impact on latency by adding the knob kern.sched.trysteal_limit to limit the topological distance of the search and don't restart the search if we detect stale results. If this search can't find an stealable thread, the idle loop can do a more complete search. Also poll for threads being assigned to this CPU during the search and switch to them instead of continuing the search. This change is responsibile for the majority of the improvement in parallel buildworld times. In sched_balance_group() change the minimum threshold from stealing a thread from 1 to 2. Poaching a newly assigned thread from a CPU that is waking up hasn't yet switched to that thread from idle is likely very rare and is likely to have the same lock race as is seen when stealing threads in the idle loop. Also use tdq_notify() to kick the destintation CPU instead of always sending an IPI. Update a stale comment, the number of transferable threads is not calculated. Reviewed by: kib (earlier version) Comments by: avg, jeff, mav MFC after: 1 month Differential Revision: https://reviews.freebsd.org/D12130
2018-02-23 00:12:51 +00:00
return (td);
- Add a simple CPU load balancing algorithm. This works by executing once a second and equalizing the load between the two most imbalanced CPU. This is intended to clear up long term load imbalances that would not be handled by the 'pull' method in sched_choose(). - Pull out some bits of sched_choose() into a kseq_move() function that moves an arbitrary thread from one kseq to another.
2003-06-09 00:39:09 +00:00
}
- Add static to local functions and data where it was missing. - Add an IPI based mechanism for migrating kses. This mechanism is broken down into several components. This is intended to reduce cache thrashing by eliminating most cases where one cpu touches another's run queues. - kseq_notify() appends a kse to a lockless singly linked list and conditionally sends an IPI to the target processor. Right now this is protected by sched_lock but at some point I'd like to get rid of the global lock. This is why I used something more complicated than a standard queue. - kseq_assign() processes our list of kses that have been assigned to us by other processors. This simply calls sched_add() for each item on the list after clearing the new KEF_ASSIGNED flag. This flag is used to indicate that we have been appeneded to the assigned queue but not added to the run queue yet. - In sched_add(), instead of adding a KSE to another processor's queue we use kse_notify() so that we don't touch their queue. Also in sched_add(), if KEF_ASSIGNED is already set return immediately. This can happen if a thread is removed and readded so that the priority is recorded properly. - In sched_rem() return immediately if KEF_ASSIGNED is set. All callers immediately readd simply to adjust priorites etc. - In sched_choose(), if we're running an IDLE task or the per cpu idle thread set our cpumask bit in 'kseq_idle' so that other processors may know that we are idle. Before this, make a single pass through the run queues of other processors so that we may find work more immediately if it is available. - In sched_runnable(), don't scan each processor's run queue, they will IPI us if they have work for us to do. - In sched_add(), if we're adding a thread that can be migrated and we have plenty of work to do, try to migrate the thread to an idle kseq. - Simplify the logic in sched_prio() and take the KEF_ASSIGNED flag into consideration. - No longer use kseq_choose() to steal threads, it can lose it's last argument. - Create a new function runq_steal() which operates like runq_choose() but skips threads based on some criteria. Currently it will not steal PRI_ITHD threads. In the future this will be used for CPU binding. - Create a kseq_steal() that checks each run queue with runq_steal(), use kseq_steal() in the places where we used kseq_choose() to steal with before.
2003-10-31 11:16:04 +00:00
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* This tdq has idled. Try to steal a thread from another cpu and switch
* to it.
*/
- Add support for CPU groups to ule. All SMT cores on the same physical cpu are added to a group. - Don't place a cpu into the kseq_idle bitmask until all cpus in that group have idled. - Prefer idle groups over idle group members in the new kseq_transfer() function. In this way we will prefer to balance load across full cores rather than add further load a partial core. - Before a cpu goes idle, check the other group members for threads. Since SMT cpus may freely share threads, this is cheap. - SMT cores may be individually pinned and bound to now. This contrasts the old mechanism where binding or pinning would have allowed a thread to run on any available cpu. - Remove some unnecessary logic from sched_switch(). Priority propagation should be properly taken care of in sched_prio() now.
2003-12-11 03:57:10 +00:00
static int
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
tdq_idled(struct tdq *tdq)
- Add static to local functions and data where it was missing. - Add an IPI based mechanism for migrating kses. This mechanism is broken down into several components. This is intended to reduce cache thrashing by eliminating most cases where one cpu touches another's run queues. - kseq_notify() appends a kse to a lockless singly linked list and conditionally sends an IPI to the target processor. Right now this is protected by sched_lock but at some point I'd like to get rid of the global lock. This is why I used something more complicated than a standard queue. - kseq_assign() processes our list of kses that have been assigned to us by other processors. This simply calls sched_add() for each item on the list after clearing the new KEF_ASSIGNED flag. This flag is used to indicate that we have been appeneded to the assigned queue but not added to the run queue yet. - In sched_add(), instead of adding a KSE to another processor's queue we use kse_notify() so that we don't touch their queue. Also in sched_add(), if KEF_ASSIGNED is already set return immediately. This can happen if a thread is removed and readded so that the priority is recorded properly. - In sched_rem() return immediately if KEF_ASSIGNED is set. All callers immediately readd simply to adjust priorites etc. - In sched_choose(), if we're running an IDLE task or the per cpu idle thread set our cpumask bit in 'kseq_idle' so that other processors may know that we are idle. Before this, make a single pass through the run queues of other processors so that we may find work more immediately if it is available. - In sched_runnable(), don't scan each processor's run queue, they will IPI us if they have work for us to do. - In sched_add(), if we're adding a thread that can be migrated and we have plenty of work to do, try to migrate the thread to an idle kseq. - Simplify the logic in sched_prio() and take the KEF_ASSIGNED flag into consideration. - No longer use kseq_choose() to steal threads, it can lose it's last argument. - Create a new function runq_steal() which operates like runq_choose() but skips threads based on some criteria. Currently it will not steal PRI_ITHD threads. In the future this will be used for CPU binding. - Create a kseq_steal() that checks each run queue with runq_steal(), use kseq_steal() in the places where we used kseq_choose() to steal with before.
2003-10-31 11:16:04 +00:00
{
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
struct cpu_group *cg;
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
struct tdq *steal;
- Use cpuset_t and the CPU_ macros in place of cpumask_t so that ULE supports arbitrary numbers of cpus rather than being limited by cpumask_t to the number of bits in a long.
2009-06-23 22:12:37 +00:00
cpuset_t mask;
Decrease latency by not wrapping the idle loop's potentially lengthy search for a thread to steal inside a critical section. Since this allows the search to be preempted, restart the search if preemption happens since the search results found earlier may no longer be valid. Decrease the latency of starting a thread that may be assigned to this CPU during the search by polling for incoming threads during the search and switching to that thread instead of continuing the search. Test for stale search results and restart the search before going through the expense of calling tdq_lock_pair(). Retry some tests after grabbing the locks since things may have changed while waiting to get both locks. Eliminate special case handling for stealing from an SMT peer that uses 1 as the steal threshold. This can only succeed if a thread has been assigned but our SMT peer has not yet started executing it. This is quite rare and when it happens the other SMT thread is generally waiting for the same tdq lock that we hold. Basically both SMT threads are racing to grab the same spin lock. Add the kern.sched.always_steal knob from a ULE patch by jeff@. Incorporate another idea from Jeff's ULE patch. If the sched_switch() detects that the CPU is about to go idle, try to steal a thread before switching to the idle thread. Since the search for a thread to steal has to be done inside a critical section in this context, limit the impact on latency by adding the knob kern.sched.trysteal_limit to limit the topological distance of the search and don't restart the search if we detect stale results. If this search can't find an stealable thread, the idle loop can do a more complete search. Also poll for threads being assigned to this CPU during the search and switch to them instead of continuing the search. This change is responsibile for the majority of the improvement in parallel buildworld times. In sched_balance_group() change the minimum threshold from stealing a thread from 1 to 2. Poaching a newly assigned thread from a CPU that is waking up hasn't yet switched to that thread from idle is likely very rare and is likely to have the same lock race as is seen when stealing threads in the idle loop. Also use tdq_notify() to kick the destintation CPU instead of always sending an IPI. Update a stale comment, the number of transferable threads is not calculated. Reviewed by: kib (earlier version) Comments by: avg, jeff, mav MFC after: 1 month Differential Revision: https://reviews.freebsd.org/D12130
2018-02-23 00:12:51 +00:00
int cpu, switchcnt;
- Add support for CPU groups to ule. All SMT cores on the same physical cpu are added to a group. - Don't place a cpu into the kseq_idle bitmask until all cpus in that group have idled. - Prefer idle groups over idle group members in the new kseq_transfer() function. In this way we will prefer to balance load across full cores rather than add further load a partial core. - Before a cpu goes idle, check the other group members for threads. Since SMT cpus may freely share threads, this is cheap. - SMT cores may be individually pinned and bound to now. This contrasts the old mechanism where binding or pinning would have allowed a thread to run on any available cpu. - Remove some unnecessary logic from sched_switch(). Priority propagation should be properly taken care of in sched_prio() now.
2003-12-11 03:57:10 +00:00
Decrease latency by not wrapping the idle loop's potentially lengthy search for a thread to steal inside a critical section. Since this allows the search to be preempted, restart the search if preemption happens since the search results found earlier may no longer be valid. Decrease the latency of starting a thread that may be assigned to this CPU during the search by polling for incoming threads during the search and switching to that thread instead of continuing the search. Test for stale search results and restart the search before going through the expense of calling tdq_lock_pair(). Retry some tests after grabbing the locks since things may have changed while waiting to get both locks. Eliminate special case handling for stealing from an SMT peer that uses 1 as the steal threshold. This can only succeed if a thread has been assigned but our SMT peer has not yet started executing it. This is quite rare and when it happens the other SMT thread is generally waiting for the same tdq lock that we hold. Basically both SMT threads are racing to grab the same spin lock. Add the kern.sched.always_steal knob from a ULE patch by jeff@. Incorporate another idea from Jeff's ULE patch. If the sched_switch() detects that the CPU is about to go idle, try to steal a thread before switching to the idle thread. Since the search for a thread to steal has to be done inside a critical section in this context, limit the impact on latency by adding the knob kern.sched.trysteal_limit to limit the topological distance of the search and don't restart the search if we detect stale results. If this search can't find an stealable thread, the idle loop can do a more complete search. Also poll for threads being assigned to this CPU during the search and switch to them instead of continuing the search. This change is responsibile for the majority of the improvement in parallel buildworld times. In sched_balance_group() change the minimum threshold from stealing a thread from 1 to 2. Poaching a newly assigned thread from a CPU that is waking up hasn't yet switched to that thread from idle is likely very rare and is likely to have the same lock race as is seen when stealing threads in the idle loop. Also use tdq_notify() to kick the destintation CPU instead of always sending an IPI. Update a stale comment, the number of transferable threads is not calculated. Reviewed by: kib (earlier version) Comments by: avg, jeff, mav MFC after: 1 month Differential Revision: https://reviews.freebsd.org/D12130
2018-02-23 00:12:51 +00:00
if (smp_started == 0 || steal_idle == 0 || tdq->tdq_cg == NULL)
- Bail out of tdq_idled if !smp_started or idle stealing is disabled. This fixes a bug on UP machines with SMP kernels where the idle thread constantly switches after trying to steal work from the local cpu. - Make the idle stealing code more robust against self selection. - Prefer to steal from the cpu with the highest load that has at least one transferable thread. Before we selected the cpu with the highest transferable count which excludes bound threads. Collaborated with: csjp Approved by: re
2007-10-08 23:50:39 +00:00
return (1);
- Use cpuset_t and the CPU_ macros in place of cpumask_t so that ULE supports arbitrary numbers of cpus rather than being limited by cpumask_t to the number of bits in a long.
2009-06-23 22:12:37 +00:00
CPU_FILL(&mask);
CPU_CLR(PCPU_GET(cpuid), &mask);
Decrease latency by not wrapping the idle loop's potentially lengthy search for a thread to steal inside a critical section. Since this allows the search to be preempted, restart the search if preemption happens since the search results found earlier may no longer be valid. Decrease the latency of starting a thread that may be assigned to this CPU during the search by polling for incoming threads during the search and switching to that thread instead of continuing the search. Test for stale search results and restart the search before going through the expense of calling tdq_lock_pair(). Retry some tests after grabbing the locks since things may have changed while waiting to get both locks. Eliminate special case handling for stealing from an SMT peer that uses 1 as the steal threshold. This can only succeed if a thread has been assigned but our SMT peer has not yet started executing it. This is quite rare and when it happens the other SMT thread is generally waiting for the same tdq lock that we hold. Basically both SMT threads are racing to grab the same spin lock. Add the kern.sched.always_steal knob from a ULE patch by jeff@. Incorporate another idea from Jeff's ULE patch. If the sched_switch() detects that the CPU is about to go idle, try to steal a thread before switching to the idle thread. Since the search for a thread to steal has to be done inside a critical section in this context, limit the impact on latency by adding the knob kern.sched.trysteal_limit to limit the topological distance of the search and don't restart the search if we detect stale results. If this search can't find an stealable thread, the idle loop can do a more complete search. Also poll for threads being assigned to this CPU during the search and switch to them instead of continuing the search. This change is responsibile for the majority of the improvement in parallel buildworld times. In sched_balance_group() change the minimum threshold from stealing a thread from 1 to 2. Poaching a newly assigned thread from a CPU that is waking up hasn't yet switched to that thread from idle is likely very rare and is likely to have the same lock race as is seen when stealing threads in the idle loop. Also use tdq_notify() to kick the destintation CPU instead of always sending an IPI. Update a stale comment, the number of transferable threads is not calculated. Reviewed by: kib (earlier version) Comments by: avg, jeff, mav MFC after: 1 month Differential Revision: https://reviews.freebsd.org/D12130
2018-02-23 00:12:51 +00:00
restart:
switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
for (cg = tdq->tdq_cg; ; ) {
cpu = sched_highest(cg, mask, steal_thresh);
/*
* We were assigned a thread but not preempted. Returning
* 0 here will cause our caller to switch to it.
*/
if (tdq->tdq_load)
return (0);
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
if (cpu == -1) {
cg = cg->cg_parent;
Decrease latency by not wrapping the idle loop's potentially lengthy search for a thread to steal inside a critical section. Since this allows the search to be preempted, restart the search if preemption happens since the search results found earlier may no longer be valid. Decrease the latency of starting a thread that may be assigned to this CPU during the search by polling for incoming threads during the search and switching to that thread instead of continuing the search. Test for stale search results and restart the search before going through the expense of calling tdq_lock_pair(). Retry some tests after grabbing the locks since things may have changed while waiting to get both locks. Eliminate special case handling for stealing from an SMT peer that uses 1 as the steal threshold. This can only succeed if a thread has been assigned but our SMT peer has not yet started executing it. This is quite rare and when it happens the other SMT thread is generally waiting for the same tdq lock that we hold. Basically both SMT threads are racing to grab the same spin lock. Add the kern.sched.always_steal knob from a ULE patch by jeff@. Incorporate another idea from Jeff's ULE patch. If the sched_switch() detects that the CPU is about to go idle, try to steal a thread before switching to the idle thread. Since the search for a thread to steal has to be done inside a critical section in this context, limit the impact on latency by adding the knob kern.sched.trysteal_limit to limit the topological distance of the search and don't restart the search if we detect stale results. If this search can't find an stealable thread, the idle loop can do a more complete search. Also poll for threads being assigned to this CPU during the search and switch to them instead of continuing the search. This change is responsibile for the majority of the improvement in parallel buildworld times. In sched_balance_group() change the minimum threshold from stealing a thread from 1 to 2. Poaching a newly assigned thread from a CPU that is waking up hasn't yet switched to that thread from idle is likely very rare and is likely to have the same lock race as is seen when stealing threads in the idle loop. Also use tdq_notify() to kick the destintation CPU instead of always sending an IPI. Update a stale comment, the number of transferable threads is not calculated. Reviewed by: kib (earlier version) Comments by: avg, jeff, mav MFC after: 1 month Differential Revision: https://reviews.freebsd.org/D12130
2018-02-23 00:12:51 +00:00
if (cg == NULL)
return (1);
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
continue;
- Add support for CPU groups to ule. All SMT cores on the same physical cpu are added to a group. - Don't place a cpu into the kseq_idle bitmask until all cpus in that group have idled. - Prefer idle groups over idle group members in the new kseq_transfer() function. In this way we will prefer to balance load across full cores rather than add further load a partial core. - Before a cpu goes idle, check the other group members for threads. Since SMT cpus may freely share threads, this is cheap. - SMT cores may be individually pinned and bound to now. This contrasts the old mechanism where binding or pinning would have allowed a thread to run on any available cpu. - Remove some unnecessary logic from sched_switch(). Priority propagation should be properly taken care of in sched_prio() now.
2003-12-11 03:57:10 +00:00
}
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
steal = TDQ_CPU(cpu);
Decrease latency by not wrapping the idle loop's potentially lengthy search for a thread to steal inside a critical section. Since this allows the search to be preempted, restart the search if preemption happens since the search results found earlier may no longer be valid. Decrease the latency of starting a thread that may be assigned to this CPU during the search by polling for incoming threads during the search and switching to that thread instead of continuing the search. Test for stale search results and restart the search before going through the expense of calling tdq_lock_pair(). Retry some tests after grabbing the locks since things may have changed while waiting to get both locks. Eliminate special case handling for stealing from an SMT peer that uses 1 as the steal threshold. This can only succeed if a thread has been assigned but our SMT peer has not yet started executing it. This is quite rare and when it happens the other SMT thread is generally waiting for the same tdq lock that we hold. Basically both SMT threads are racing to grab the same spin lock. Add the kern.sched.always_steal knob from a ULE patch by jeff@. Incorporate another idea from Jeff's ULE patch. If the sched_switch() detects that the CPU is about to go idle, try to steal a thread before switching to the idle thread. Since the search for a thread to steal has to be done inside a critical section in this context, limit the impact on latency by adding the knob kern.sched.trysteal_limit to limit the topological distance of the search and don't restart the search if we detect stale results. If this search can't find an stealable thread, the idle loop can do a more complete search. Also poll for threads being assigned to this CPU during the search and switch to them instead of continuing the search. This change is responsibile for the majority of the improvement in parallel buildworld times. In sched_balance_group() change the minimum threshold from stealing a thread from 1 to 2. Poaching a newly assigned thread from a CPU that is waking up hasn't yet switched to that thread from idle is likely very rare and is likely to have the same lock race as is seen when stealing threads in the idle loop. Also use tdq_notify() to kick the destintation CPU instead of always sending an IPI. Update a stale comment, the number of transferable threads is not calculated. Reviewed by: kib (earlier version) Comments by: avg, jeff, mav MFC after: 1 month Differential Revision: https://reviews.freebsd.org/D12130
2018-02-23 00:12:51 +00:00
/*
* The data returned by sched_highest() is stale and
* the chosen CPU no longer has an eligible thread.
*
* Testing this ahead of tdq_lock_pair() only catches
* this situation about 20% of the time on an 8 core
* 16 thread Ryzen 7, but it still helps performance.
*/
if (steal->tdq_load < steal_thresh ||
steal->tdq_transferable == 0)
goto restart;
- Move the rebalancer back into hardclock to prevent potential softclock starvation caused by unbalanced interrupt loads. - Change the rebalancer to work on stathz ticks but retain randomization. - Simplify locking in tdq_idled() to use the tdq_lock_pair() rather than complex sequences of locks to avoid deadlock. Reported by: kris Approved by: re
2007-10-02 00:36:06 +00:00
tdq_lock_pair(tdq, steal);
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
/*
Decrease latency by not wrapping the idle loop's potentially lengthy search for a thread to steal inside a critical section. Since this allows the search to be preempted, restart the search if preemption happens since the search results found earlier may no longer be valid. Decrease the latency of starting a thread that may be assigned to this CPU during the search by polling for incoming threads during the search and switching to that thread instead of continuing the search. Test for stale search results and restart the search before going through the expense of calling tdq_lock_pair(). Retry some tests after grabbing the locks since things may have changed while waiting to get both locks. Eliminate special case handling for stealing from an SMT peer that uses 1 as the steal threshold. This can only succeed if a thread has been assigned but our SMT peer has not yet started executing it. This is quite rare and when it happens the other SMT thread is generally waiting for the same tdq lock that we hold. Basically both SMT threads are racing to grab the same spin lock. Add the kern.sched.always_steal knob from a ULE patch by jeff@. Incorporate another idea from Jeff's ULE patch. If the sched_switch() detects that the CPU is about to go idle, try to steal a thread before switching to the idle thread. Since the search for a thread to steal has to be done inside a critical section in this context, limit the impact on latency by adding the knob kern.sched.trysteal_limit to limit the topological distance of the search and don't restart the search if we detect stale results. If this search can't find an stealable thread, the idle loop can do a more complete search. Also poll for threads being assigned to this CPU during the search and switch to them instead of continuing the search. This change is responsibile for the majority of the improvement in parallel buildworld times. In sched_balance_group() change the minimum threshold from stealing a thread from 1 to 2. Poaching a newly assigned thread from a CPU that is waking up hasn't yet switched to that thread from idle is likely very rare and is likely to have the same lock race as is seen when stealing threads in the idle loop. Also use tdq_notify() to kick the destintation CPU instead of always sending an IPI. Update a stale comment, the number of transferable threads is not calculated. Reviewed by: kib (earlier version) Comments by: avg, jeff, mav MFC after: 1 month Differential Revision: https://reviews.freebsd.org/D12130
2018-02-23 00:12:51 +00:00
* We were assigned a thread while waiting for the locks.
* Switch to it now instead of stealing a thread.
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
*/
Decrease latency by not wrapping the idle loop's potentially lengthy search for a thread to steal inside a critical section. Since this allows the search to be preempted, restart the search if preemption happens since the search results found earlier may no longer be valid. Decrease the latency of starting a thread that may be assigned to this CPU during the search by polling for incoming threads during the search and switching to that thread instead of continuing the search. Test for stale search results and restart the search before going through the expense of calling tdq_lock_pair(). Retry some tests after grabbing the locks since things may have changed while waiting to get both locks. Eliminate special case handling for stealing from an SMT peer that uses 1 as the steal threshold. This can only succeed if a thread has been assigned but our SMT peer has not yet started executing it. This is quite rare and when it happens the other SMT thread is generally waiting for the same tdq lock that we hold. Basically both SMT threads are racing to grab the same spin lock. Add the kern.sched.always_steal knob from a ULE patch by jeff@. Incorporate another idea from Jeff's ULE patch. If the sched_switch() detects that the CPU is about to go idle, try to steal a thread before switching to the idle thread. Since the search for a thread to steal has to be done inside a critical section in this context, limit the impact on latency by adding the knob kern.sched.trysteal_limit to limit the topological distance of the search and don't restart the search if we detect stale results. If this search can't find an stealable thread, the idle loop can do a more complete search. Also poll for threads being assigned to this CPU during the search and switch to them instead of continuing the search. This change is responsibile for the majority of the improvement in parallel buildworld times. In sched_balance_group() change the minimum threshold from stealing a thread from 1 to 2. Poaching a newly assigned thread from a CPU that is waking up hasn't yet switched to that thread from idle is likely very rare and is likely to have the same lock race as is seen when stealing threads in the idle loop. Also use tdq_notify() to kick the destintation CPU instead of always sending an IPI. Update a stale comment, the number of transferable threads is not calculated. Reviewed by: kib (earlier version) Comments by: avg, jeff, mav MFC after: 1 month Differential Revision: https://reviews.freebsd.org/D12130
2018-02-23 00:12:51 +00:00
if (tdq->tdq_load)
break;
/*
* The data returned by sched_highest() is stale and
* the chosen CPU no longer has an eligible thread, or
* we were preempted and the CPU loading info may be out
* of date. The latter is rare. In either case restart
* the search.
*/
if (steal->tdq_load < steal_thresh ||
steal->tdq_transferable == 0 ||
switchcnt != tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt) {
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
tdq_unlock_pair(tdq, steal);
Decrease latency by not wrapping the idle loop's potentially lengthy search for a thread to steal inside a critical section. Since this allows the search to be preempted, restart the search if preemption happens since the search results found earlier may no longer be valid. Decrease the latency of starting a thread that may be assigned to this CPU during the search by polling for incoming threads during the search and switching to that thread instead of continuing the search. Test for stale search results and restart the search before going through the expense of calling tdq_lock_pair(). Retry some tests after grabbing the locks since things may have changed while waiting to get both locks. Eliminate special case handling for stealing from an SMT peer that uses 1 as the steal threshold. This can only succeed if a thread has been assigned but our SMT peer has not yet started executing it. This is quite rare and when it happens the other SMT thread is generally waiting for the same tdq lock that we hold. Basically both SMT threads are racing to grab the same spin lock. Add the kern.sched.always_steal knob from a ULE patch by jeff@. Incorporate another idea from Jeff's ULE patch. If the sched_switch() detects that the CPU is about to go idle, try to steal a thread before switching to the idle thread. Since the search for a thread to steal has to be done inside a critical section in this context, limit the impact on latency by adding the knob kern.sched.trysteal_limit to limit the topological distance of the search and don't restart the search if we detect stale results. If this search can't find an stealable thread, the idle loop can do a more complete search. Also poll for threads being assigned to this CPU during the search and switch to them instead of continuing the search. This change is responsibile for the majority of the improvement in parallel buildworld times. In sched_balance_group() change the minimum threshold from stealing a thread from 1 to 2. Poaching a newly assigned thread from a CPU that is waking up hasn't yet switched to that thread from idle is likely very rare and is likely to have the same lock race as is seen when stealing threads in the idle loop. Also use tdq_notify() to kick the destintation CPU instead of always sending an IPI. Update a stale comment, the number of transferable threads is not calculated. Reviewed by: kib (earlier version) Comments by: avg, jeff, mav MFC after: 1 month Differential Revision: https://reviews.freebsd.org/D12130
2018-02-23 00:12:51 +00:00
goto restart;
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
}
Decrease latency by not wrapping the idle loop's potentially lengthy search for a thread to steal inside a critical section. Since this allows the search to be preempted, restart the search if preemption happens since the search results found earlier may no longer be valid. Decrease the latency of starting a thread that may be assigned to this CPU during the search by polling for incoming threads during the search and switching to that thread instead of continuing the search. Test for stale search results and restart the search before going through the expense of calling tdq_lock_pair(). Retry some tests after grabbing the locks since things may have changed while waiting to get both locks. Eliminate special case handling for stealing from an SMT peer that uses 1 as the steal threshold. This can only succeed if a thread has been assigned but our SMT peer has not yet started executing it. This is quite rare and when it happens the other SMT thread is generally waiting for the same tdq lock that we hold. Basically both SMT threads are racing to grab the same spin lock. Add the kern.sched.always_steal knob from a ULE patch by jeff@. Incorporate another idea from Jeff's ULE patch. If the sched_switch() detects that the CPU is about to go idle, try to steal a thread before switching to the idle thread. Since the search for a thread to steal has to be done inside a critical section in this context, limit the impact on latency by adding the knob kern.sched.trysteal_limit to limit the topological distance of the search and don't restart the search if we detect stale results. If this search can't find an stealable thread, the idle loop can do a more complete search. Also poll for threads being assigned to this CPU during the search and switch to them instead of continuing the search. This change is responsibile for the majority of the improvement in parallel buildworld times. In sched_balance_group() change the minimum threshold from stealing a thread from 1 to 2. Poaching a newly assigned thread from a CPU that is waking up hasn't yet switched to that thread from idle is likely very rare and is likely to have the same lock race as is seen when stealing threads in the idle loop. Also use tdq_notify() to kick the destintation CPU instead of always sending an IPI. Update a stale comment, the number of transferable threads is not calculated. Reviewed by: kib (earlier version) Comments by: avg, jeff, mav MFC after: 1 month Differential Revision: https://reviews.freebsd.org/D12130
2018-02-23 00:12:51 +00:00
/*
* Steal the thread and switch to it.
*/
if (tdq_move(steal, tdq) != NULL)
break;
/*
* We failed to acquire a thread even though it looked
* like one was available. This could be due to affinity
* restrictions or for other reasons. Loop again after
* removing this CPU from the set. The restart logic
* above does not restore this CPU to the set due to the
* likelyhood of failing here again.
*/
CPU_CLR(cpu, &mask);
tdq_unlock_pair(tdq, steal);
- Add support for CPU groups to ule. All SMT cores on the same physical cpu are added to a group. - Don't place a cpu into the kseq_idle bitmask until all cpus in that group have idled. - Prefer idle groups over idle group members in the new kseq_transfer() function. In this way we will prefer to balance load across full cores rather than add further load a partial core. - Before a cpu goes idle, check the other group members for threads. Since SMT cpus may freely share threads, this is cheap. - SMT cores may be individually pinned and bound to now. This contrasts the old mechanism where binding or pinning would have allowed a thread to run on any available cpu. - Remove some unnecessary logic from sched_switch(). Priority propagation should be properly taken care of in sched_prio() now.
2003-12-11 03:57:10 +00:00
}
Decrease latency by not wrapping the idle loop's potentially lengthy search for a thread to steal inside a critical section. Since this allows the search to be preempted, restart the search if preemption happens since the search results found earlier may no longer be valid. Decrease the latency of starting a thread that may be assigned to this CPU during the search by polling for incoming threads during the search and switching to that thread instead of continuing the search. Test for stale search results and restart the search before going through the expense of calling tdq_lock_pair(). Retry some tests after grabbing the locks since things may have changed while waiting to get both locks. Eliminate special case handling for stealing from an SMT peer that uses 1 as the steal threshold. This can only succeed if a thread has been assigned but our SMT peer has not yet started executing it. This is quite rare and when it happens the other SMT thread is generally waiting for the same tdq lock that we hold. Basically both SMT threads are racing to grab the same spin lock. Add the kern.sched.always_steal knob from a ULE patch by jeff@. Incorporate another idea from Jeff's ULE patch. If the sched_switch() detects that the CPU is about to go idle, try to steal a thread before switching to the idle thread. Since the search for a thread to steal has to be done inside a critical section in this context, limit the impact on latency by adding the knob kern.sched.trysteal_limit to limit the topological distance of the search and don't restart the search if we detect stale results. If this search can't find an stealable thread, the idle loop can do a more complete search. Also poll for threads being assigned to this CPU during the search and switch to them instead of continuing the search. This change is responsibile for the majority of the improvement in parallel buildworld times. In sched_balance_group() change the minimum threshold from stealing a thread from 1 to 2. Poaching a newly assigned thread from a CPU that is waking up hasn't yet switched to that thread from idle is likely very rare and is likely to have the same lock race as is seen when stealing threads in the idle loop. Also use tdq_notify() to kick the destintation CPU instead of always sending an IPI. Update a stale comment, the number of transferable threads is not calculated. Reviewed by: kib (earlier version) Comments by: avg, jeff, mav MFC after: 1 month Differential Revision: https://reviews.freebsd.org/D12130
2018-02-23 00:12:51 +00:00
TDQ_UNLOCK(steal);
mi_switch(SW_VOL | SWT_IDLE, NULL);
thread_unlock(curthread);
return (0);
- Add static to local functions and data where it was missing. - Add an IPI based mechanism for migrating kses. This mechanism is broken down into several components. This is intended to reduce cache thrashing by eliminating most cases where one cpu touches another's run queues. - kseq_notify() appends a kse to a lockless singly linked list and conditionally sends an IPI to the target processor. Right now this is protected by sched_lock but at some point I'd like to get rid of the global lock. This is why I used something more complicated than a standard queue. - kseq_assign() processes our list of kses that have been assigned to us by other processors. This simply calls sched_add() for each item on the list after clearing the new KEF_ASSIGNED flag. This flag is used to indicate that we have been appeneded to the assigned queue but not added to the run queue yet. - In sched_add(), instead of adding a KSE to another processor's queue we use kse_notify() so that we don't touch their queue. Also in sched_add(), if KEF_ASSIGNED is already set return immediately. This can happen if a thread is removed and readded so that the priority is recorded properly. - In sched_rem() return immediately if KEF_ASSIGNED is set. All callers immediately readd simply to adjust priorites etc. - In sched_choose(), if we're running an IDLE task or the per cpu idle thread set our cpumask bit in 'kseq_idle' so that other processors may know that we are idle. Before this, make a single pass through the run queues of other processors so that we may find work more immediately if it is available. - In sched_runnable(), don't scan each processor's run queue, they will IPI us if they have work for us to do. - In sched_add(), if we're adding a thread that can be migrated and we have plenty of work to do, try to migrate the thread to an idle kseq. - Simplify the logic in sched_prio() and take the KEF_ASSIGNED flag into consideration. - No longer use kseq_choose() to steal threads, it can lose it's last argument. - Create a new function runq_steal() which operates like runq_choose() but skips threads based on some criteria. Currently it will not steal PRI_ITHD threads. In the future this will be used for CPU binding. - Create a kseq_steal() that checks each run queue with runq_steal(), use kseq_steal() in the places where we used kseq_choose() to steal with before.
2003-10-31 11:16:04 +00:00
}
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* Notify a remote cpu of new work. Sends an IPI if criteria are met.
*/
- Add static to local functions and data where it was missing. - Add an IPI based mechanism for migrating kses. This mechanism is broken down into several components. This is intended to reduce cache thrashing by eliminating most cases where one cpu touches another's run queues. - kseq_notify() appends a kse to a lockless singly linked list and conditionally sends an IPI to the target processor. Right now this is protected by sched_lock but at some point I'd like to get rid of the global lock. This is why I used something more complicated than a standard queue. - kseq_assign() processes our list of kses that have been assigned to us by other processors. This simply calls sched_add() for each item on the list after clearing the new KEF_ASSIGNED flag. This flag is used to indicate that we have been appeneded to the assigned queue but not added to the run queue yet. - In sched_add(), instead of adding a KSE to another processor's queue we use kse_notify() so that we don't touch their queue. Also in sched_add(), if KEF_ASSIGNED is already set return immediately. This can happen if a thread is removed and readded so that the priority is recorded properly. - In sched_rem() return immediately if KEF_ASSIGNED is set. All callers immediately readd simply to adjust priorites etc. - In sched_choose(), if we're running an IDLE task or the per cpu idle thread set our cpumask bit in 'kseq_idle' so that other processors may know that we are idle. Before this, make a single pass through the run queues of other processors so that we may find work more immediately if it is available. - In sched_runnable(), don't scan each processor's run queue, they will IPI us if they have work for us to do. - In sched_add(), if we're adding a thread that can be migrated and we have plenty of work to do, try to migrate the thread to an idle kseq. - Simplify the logic in sched_prio() and take the KEF_ASSIGNED flag into consideration. - No longer use kseq_choose() to steal threads, it can lose it's last argument. - Create a new function runq_steal() which operates like runq_choose() but skips threads based on some criteria. Currently it will not steal PRI_ITHD threads. In the future this will be used for CPU binding. - Create a kseq_steal() that checks each run queue with runq_steal(), use kseq_steal() in the places where we used kseq_choose() to steal with before.
2003-10-31 11:16:04 +00:00
static void
Revert r313814 and r313816 Something evidently got mangled in my git tree in between testing and review, as an old and broken version of the patch was apparently submitted to svn. Revert this while I work out what went wrong. Reported by: tuexen Pointy hat to: rstone
2017-02-16 21:18:31 +00:00
tdq_notify(struct tdq *tdq, struct thread *td)
- Add static to local functions and data where it was missing. - Add an IPI based mechanism for migrating kses. This mechanism is broken down into several components. This is intended to reduce cache thrashing by eliminating most cases where one cpu touches another's run queues. - kseq_notify() appends a kse to a lockless singly linked list and conditionally sends an IPI to the target processor. Right now this is protected by sched_lock but at some point I'd like to get rid of the global lock. This is why I used something more complicated than a standard queue. - kseq_assign() processes our list of kses that have been assigned to us by other processors. This simply calls sched_add() for each item on the list after clearing the new KEF_ASSIGNED flag. This flag is used to indicate that we have been appeneded to the assigned queue but not added to the run queue yet. - In sched_add(), instead of adding a KSE to another processor's queue we use kse_notify() so that we don't touch their queue. Also in sched_add(), if KEF_ASSIGNED is already set return immediately. This can happen if a thread is removed and readded so that the priority is recorded properly. - In sched_rem() return immediately if KEF_ASSIGNED is set. All callers immediately readd simply to adjust priorites etc. - In sched_choose(), if we're running an IDLE task or the per cpu idle thread set our cpumask bit in 'kseq_idle' so that other processors may know that we are idle. Before this, make a single pass through the run queues of other processors so that we may find work more immediately if it is available. - In sched_runnable(), don't scan each processor's run queue, they will IPI us if they have work for us to do. - In sched_add(), if we're adding a thread that can be migrated and we have plenty of work to do, try to migrate the thread to an idle kseq. - Simplify the logic in sched_prio() and take the KEF_ASSIGNED flag into consideration. - No longer use kseq_choose() to steal threads, it can lose it's last argument. - Create a new function runq_steal() which operates like runq_choose() but skips threads based on some criteria. Currently it will not steal PRI_ITHD threads. In the future this will be used for CPU binding. - Create a kseq_steal() that checks each run queue with runq_steal(), use kseq_steal() in the places where we used kseq_choose() to steal with before.
2003-10-31 11:16:04 +00:00
{
When checking to see if another CPU is running its idle thread, examine the thread running on the other CPU instead of the thread being placed on the run queue. Reported by: Ravi Murty @ Intel Reviewed by: jeff
2008-11-18 05:41:34 +00:00
struct thread *ctd;
Revert r313814 and r313816 Something evidently got mangled in my git tree in between testing and review, as an old and broken version of the patch was apparently submitted to svn. Revert this while I work out what went wrong. Reported by: tuexen Pointy hat to: rstone
2017-02-16 21:18:31 +00:00
int pri;
Major revamp of ULE's cpu load balancing: - Switch back to direct modification of remote CPU run queues. This added a lot of complexity with questionable gain. It's easy enough to reimplement if it's shown to help on huge machines. - Re-implement the old tdq_transfer() call as tdq_pickidle(). Change sched_add() so we have selectable cpu choosers and simplify the logic a bit here. - Implement tdq_pickpri() as the new default cpu chooser. This algorithm is similar to Solaris in that it tries to always run the threads with the best priorities. It is actually slightly more complex than solaris's algorithm because we also tend to favor the local cpu over other cpus which has a boost in latency but also potentially enables cache sharing between the waking thread and the woken thread. - Add a bunch of tunables that can be used to measure effects of different load balancing strategies. Most of these will go away once the algorithm is more definite. - Add a new mechanism to steal threads from busy cpus when we idle. This is enabled with kern.sched.steal_busy and kern.sched.busy_thresh. The threshold is the required length of a tdq's run queue before another cpu will be able to steal runnable threads. This prevents most queue imbalances that contribute the long latencies.
2007-01-19 21:56:08 +00:00
int cpu;
- Add static to local functions and data where it was missing. - Add an IPI based mechanism for migrating kses. This mechanism is broken down into several components. This is intended to reduce cache thrashing by eliminating most cases where one cpu touches another's run queues. - kseq_notify() appends a kse to a lockless singly linked list and conditionally sends an IPI to the target processor. Right now this is protected by sched_lock but at some point I'd like to get rid of the global lock. This is why I used something more complicated than a standard queue. - kseq_assign() processes our list of kses that have been assigned to us by other processors. This simply calls sched_add() for each item on the list after clearing the new KEF_ASSIGNED flag. This flag is used to indicate that we have been appeneded to the assigned queue but not added to the run queue yet. - In sched_add(), instead of adding a KSE to another processor's queue we use kse_notify() so that we don't touch their queue. Also in sched_add(), if KEF_ASSIGNED is already set return immediately. This can happen if a thread is removed and readded so that the priority is recorded properly. - In sched_rem() return immediately if KEF_ASSIGNED is set. All callers immediately readd simply to adjust priorites etc. - In sched_choose(), if we're running an IDLE task or the per cpu idle thread set our cpumask bit in 'kseq_idle' so that other processors may know that we are idle. Before this, make a single pass through the run queues of other processors so that we may find work more immediately if it is available. - In sched_runnable(), don't scan each processor's run queue, they will IPI us if they have work for us to do. - In sched_add(), if we're adding a thread that can be migrated and we have plenty of work to do, try to migrate the thread to an idle kseq. - Simplify the logic in sched_prio() and take the KEF_ASSIGNED flag into consideration. - No longer use kseq_choose() to steal threads, it can lose it's last argument. - Create a new function runq_steal() which operates like runq_choose() but skips threads based on some criteria. Currently it will not steal PRI_ITHD threads. In the future this will be used for CPU binding. - Create a kseq_steal() that checks each run queue with runq_steal(), use kseq_steal() in the places where we used kseq_choose() to steal with before.
2003-10-31 11:16:04 +00:00
- Add an implementation of sched_preempt() that avoids excessive IPIs. - Normalize the preemption/ipi setting code by introducing sched_shouldpreempt() so the logical is identical and not repeated between tdq_notify() and sched_setpreempt(). - In tdq_notify() don't set NEEDRESCHED as we may not actually own the thread lock this could have caused us to lose td_flags settings. - Garbage collect some tunables that are no longer relevant.
2008-03-10 01:32:01 +00:00
if (tdq->tdq_ipipending)
return;
Revert r313814 and r313816 Something evidently got mangled in my git tree in between testing and review, as an old and broken version of the patch was apparently submitted to svn. Revert this while I work out what went wrong. Reported by: tuexen Pointy hat to: rstone
2017-02-16 21:18:31 +00:00
cpu = td_get_sched(td)->ts_cpu;
pri = td->td_priority;
When checking to see if another CPU is running its idle thread, examine the thread running on the other CPU instead of the thread being placed on the run queue. Reported by: Ravi Murty @ Intel Reviewed by: jeff
2008-11-18 05:41:34 +00:00
ctd = pcpu_find(cpu)->pc_curthread;
if (!sched_shouldpreempt(pri, ctd->td_priority, 1))
- Fix a comparison in sched_choose() that caused cpus to be constantly marked idle, thus breaking cpu load balancing. - Change sched_interact_update() to fix cases where the stored history has expanded significantly rather than handling them in the callers. This fixes a case where sched_priority() could compute a bad value. - Add a sysctl to disable the global load balancer for experimentation.
2007-01-05 23:45:38 +00:00
return;
Add comments describing r271604 change. MFC after: 3 days
2014-09-15 11:17:36 +00:00
/*
Reprase r271616 comments. Submitted by: alc MFC after: 1 month
2014-09-17 17:43:32 +00:00
* Make sure that our caller's earlier update to tdq_load is
* globally visible before we read tdq_cpu_idle. Idle thread
Add comments describing r271604 change. MFC after: 3 days
2014-09-15 11:17:36 +00:00
* accesses both of them without locks, and the order is important.
*/
Change the mb() use in the sched_ult tdq_notify() and sched_idletd() to more C11-ish atomic_thread_fence_seq_cst(). Note that on PowerPC, which currently uses lwsync for mb(), the change actually fixes the missed store/load barrier, intended by r271604 [*]. Reviewed by: alc Noted by: alc [*] Sponsored by: The FreeBSD Foundation MFC after: 3 weeks
2015-07-10 08:54:12 +00:00
atomic_thread_fence_seq_cst();
Add comments describing r271604 change. MFC after: 3 days
2014-09-15 11:17:36 +00:00
When checking to see if another CPU is running its idle thread, examine the thread running on the other CPU instead of the thread being placed on the run queue. Reported by: Ravi Murty @ Intel Reviewed by: jeff
2008-11-18 05:41:34 +00:00
if (TD_IS_IDLETHREAD(ctd)) {
- Add an integer argument to idle to indicate how likely we are to wake from idle over the next tick. - Add a new MD routine, cpu_wake_idle() to wakeup idle threads who are suspended in cpu specific states. This function can fail and cause the scheduler to fall back to another mechanism (ipi). - Implement support for mwait in cpu_idle() on i386/amd64 machines that support it. mwait is a higher performance way to synchronize cpus as compared to hlt & ipis. - Allow selecting the idle routine by name via sysctl machdep.idle. This replaces machdep.cpu_idle_hlt. Only idle routines supported by the current machine are permitted. Sponsored by: Nokia
2008-04-25 05:18:50 +00:00
/*
* If the MD code has an idle wakeup routine try that before
* falling back to IPI.
*/
Do not IPI CPU that is already spinning for load. It doubles effect of spining (comparing to MWAIT) on some heavly switching test loads.
2010-09-10 13:24:47 +00:00
if (!tdq->tdq_cpu_idle || cpu_idle_wakeup(cpu))
- Add an integer argument to idle to indicate how likely we are to wake from idle over the next tick. - Add a new MD routine, cpu_wake_idle() to wakeup idle threads who are suspended in cpu specific states. This function can fail and cause the scheduler to fall back to another mechanism (ipi). - Implement support for mwait in cpu_idle() on i386/amd64 machines that support it. mwait is a higher performance way to synchronize cpus as compared to hlt & ipis. - Allow selecting the idle routine by name via sysctl machdep.idle. This replaces machdep.cpu_idle_hlt. Only idle routines supported by the current machine are permitted. Sponsored by: Nokia
2008-04-25 05:18:50 +00:00
return;
- Add a metric to describe how busy a processor has been over the last two ticks by counting the number of switches and the load when sched_clock() is called. - If the busy metric exceeds a threshold allow the idle thread to spin waiting for new work for a brief period to avoid using IPIs. This reduces the cost on the sender and receiver as well as reducing wakeup latency considerably when it works. Sponsored by: Nokia
2008-04-17 09:56:01 +00:00
}
- Add an implementation of sched_preempt() that avoids excessive IPIs. - Normalize the preemption/ipi setting code by introducing sched_shouldpreempt() so the logical is identical and not repeated between tdq_notify() and sched_setpreempt(). - In tdq_notify() don't set NEEDRESCHED as we may not actually own the thread lock this could have caused us to lose td_flags settings. - Garbage collect some tunables that are no longer relevant.
2008-03-10 01:32:01 +00:00
tdq->tdq_ipipending = 1;
Add a new ipi_cpu() function to the MI IPI API that can be used to send an IPI to a specific CPU by its cpuid. Replace calls to ipi_selected() that constructed a mask for a single CPU with calls to ipi_cpu() instead. This will matter more in the future when we transition from cpumask_t to cpuset_t for CPU masks in which case building a CPU mask is more expensive. Submitted by: peter, sbruno Reviewed by: rookie Obtained from: Yahoo! (x86) MFC after: 1 month
2010-08-06 15:36:59 +00:00
ipi_cpu(cpu, IPI_PREEMPT);
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
}
/*
* Steals load from a timeshare queue. Honors the rotating queue head
* index.
*/
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
static struct thread *
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
runq_steal_from(struct runq *rq, int cpu, u_char start)
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
{
struct rqbits *rqb;
struct rqhead *rqh;
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
struct thread *td, *first;
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
int bit;
int i;
rqb = &rq->rq_status;
bit = start & (RQB_BPW -1);
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
first = NULL;
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
again:
for (i = RQB_WORD(start); i < RQB_LEN; bit = 0, i++) {
if (rqb->rqb_bits[i] == 0)
continue;
- Make runq_steal_from more aggressive. Previously it would examine only a single priority queue. If that queue had a thread or threads which could not be migrated we would fail to steal load. This could cause starvation in situations where cores are idle. Submitted by: Doug Kilpatrick <dkilpatrick@isilon.com> Tested by: pho Reviewed by: mav Sponsored by: EMC / Isilon Storage Division
2014-03-08 00:35:06 +00:00
if (bit == 0)
bit = RQB_FFS(rqb->rqb_bits[i]);
for (; bit < RQB_BPW; bit++) {
if ((rqb->rqb_bits[i] & (1ul << bit)) == 0)
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
continue;
- Make runq_steal_from more aggressive. Previously it would examine only a single priority queue. If that queue had a thread or threads which could not be migrated we would fail to steal load. This could cause starvation in situations where cores are idle. Submitted by: Doug Kilpatrick <dkilpatrick@isilon.com> Tested by: pho Reviewed by: mav Sponsored by: EMC / Isilon Storage Division
2014-03-08 00:35:06 +00:00
rqh = &rq->rq_queues[bit + (i << RQB_L2BPW)];
TAILQ_FOREACH(td, rqh, td_runq) {
if (first && THREAD_CAN_MIGRATE(td) &&
THREAD_CAN_SCHED(td, cpu))
return (td);
first = td;
}
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
}
}
if (start != 0) {
start = 0;
goto again;
}
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
if (first && THREAD_CAN_MIGRATE(first) &&
THREAD_CAN_SCHED(first, cpu))
return (first);
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
return (NULL);
- Add static to local functions and data where it was missing. - Add an IPI based mechanism for migrating kses. This mechanism is broken down into several components. This is intended to reduce cache thrashing by eliminating most cases where one cpu touches another's run queues. - kseq_notify() appends a kse to a lockless singly linked list and conditionally sends an IPI to the target processor. Right now this is protected by sched_lock but at some point I'd like to get rid of the global lock. This is why I used something more complicated than a standard queue. - kseq_assign() processes our list of kses that have been assigned to us by other processors. This simply calls sched_add() for each item on the list after clearing the new KEF_ASSIGNED flag. This flag is used to indicate that we have been appeneded to the assigned queue but not added to the run queue yet. - In sched_add(), instead of adding a KSE to another processor's queue we use kse_notify() so that we don't touch their queue. Also in sched_add(), if KEF_ASSIGNED is already set return immediately. This can happen if a thread is removed and readded so that the priority is recorded properly. - In sched_rem() return immediately if KEF_ASSIGNED is set. All callers immediately readd simply to adjust priorites etc. - In sched_choose(), if we're running an IDLE task or the per cpu idle thread set our cpumask bit in 'kseq_idle' so that other processors may know that we are idle. Before this, make a single pass through the run queues of other processors so that we may find work more immediately if it is available. - In sched_runnable(), don't scan each processor's run queue, they will IPI us if they have work for us to do. - In sched_add(), if we're adding a thread that can be migrated and we have plenty of work to do, try to migrate the thread to an idle kseq. - Simplify the logic in sched_prio() and take the KEF_ASSIGNED flag into consideration. - No longer use kseq_choose() to steal threads, it can lose it's last argument. - Create a new function runq_steal() which operates like runq_choose() but skips threads based on some criteria. Currently it will not steal PRI_ITHD threads. In the future this will be used for CPU binding. - Create a kseq_steal() that checks each run queue with runq_steal(), use kseq_steal() in the places where we used kseq_choose() to steal with before.
2003-10-31 11:16:04 +00:00
}
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* Steals load from a standard linear queue.
*/
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
static struct thread *
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
runq_steal(struct runq *rq, int cpu)
- Add static to local functions and data where it was missing. - Add an IPI based mechanism for migrating kses. This mechanism is broken down into several components. This is intended to reduce cache thrashing by eliminating most cases where one cpu touches another's run queues. - kseq_notify() appends a kse to a lockless singly linked list and conditionally sends an IPI to the target processor. Right now this is protected by sched_lock but at some point I'd like to get rid of the global lock. This is why I used something more complicated than a standard queue. - kseq_assign() processes our list of kses that have been assigned to us by other processors. This simply calls sched_add() for each item on the list after clearing the new KEF_ASSIGNED flag. This flag is used to indicate that we have been appeneded to the assigned queue but not added to the run queue yet. - In sched_add(), instead of adding a KSE to another processor's queue we use kse_notify() so that we don't touch their queue. Also in sched_add(), if KEF_ASSIGNED is already set return immediately. This can happen if a thread is removed and readded so that the priority is recorded properly. - In sched_rem() return immediately if KEF_ASSIGNED is set. All callers immediately readd simply to adjust priorites etc. - In sched_choose(), if we're running an IDLE task or the per cpu idle thread set our cpumask bit in 'kseq_idle' so that other processors may know that we are idle. Before this, make a single pass through the run queues of other processors so that we may find work more immediately if it is available. - In sched_runnable(), don't scan each processor's run queue, they will IPI us if they have work for us to do. - In sched_add(), if we're adding a thread that can be migrated and we have plenty of work to do, try to migrate the thread to an idle kseq. - Simplify the logic in sched_prio() and take the KEF_ASSIGNED flag into consideration. - No longer use kseq_choose() to steal threads, it can lose it's last argument. - Create a new function runq_steal() which operates like runq_choose() but skips threads based on some criteria. Currently it will not steal PRI_ITHD threads. In the future this will be used for CPU binding. - Create a kseq_steal() that checks each run queue with runq_steal(), use kseq_steal() in the places where we used kseq_choose() to steal with before.
2003-10-31 11:16:04 +00:00
{
struct rqhead *rqh;
struct rqbits *rqb;
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
struct thread *td;
- Add static to local functions and data where it was missing. - Add an IPI based mechanism for migrating kses. This mechanism is broken down into several components. This is intended to reduce cache thrashing by eliminating most cases where one cpu touches another's run queues. - kseq_notify() appends a kse to a lockless singly linked list and conditionally sends an IPI to the target processor. Right now this is protected by sched_lock but at some point I'd like to get rid of the global lock. This is why I used something more complicated than a standard queue. - kseq_assign() processes our list of kses that have been assigned to us by other processors. This simply calls sched_add() for each item on the list after clearing the new KEF_ASSIGNED flag. This flag is used to indicate that we have been appeneded to the assigned queue but not added to the run queue yet. - In sched_add(), instead of adding a KSE to another processor's queue we use kse_notify() so that we don't touch their queue. Also in sched_add(), if KEF_ASSIGNED is already set return immediately. This can happen if a thread is removed and readded so that the priority is recorded properly. - In sched_rem() return immediately if KEF_ASSIGNED is set. All callers immediately readd simply to adjust priorites etc. - In sched_choose(), if we're running an IDLE task or the per cpu idle thread set our cpumask bit in 'kseq_idle' so that other processors may know that we are idle. Before this, make a single pass through the run queues of other processors so that we may find work more immediately if it is available. - In sched_runnable(), don't scan each processor's run queue, they will IPI us if they have work for us to do. - In sched_add(), if we're adding a thread that can be migrated and we have plenty of work to do, try to migrate the thread to an idle kseq. - Simplify the logic in sched_prio() and take the KEF_ASSIGNED flag into consideration. - No longer use kseq_choose() to steal threads, it can lose it's last argument. - Create a new function runq_steal() which operates like runq_choose() but skips threads based on some criteria. Currently it will not steal PRI_ITHD threads. In the future this will be used for CPU binding. - Create a kseq_steal() that checks each run queue with runq_steal(), use kseq_steal() in the places where we used kseq_choose() to steal with before.
2003-10-31 11:16:04 +00:00
int word;
int bit;
rqb = &rq->rq_status;
for (word = 0; word < RQB_LEN; word++) {
if (rqb->rqb_bits[word] == 0)
continue;
for (bit = 0; bit < RQB_BPW; bit++) {
rqb_bits[] may be an int64_t (eg: on alpha, and recently on amd64). Be sure to shift (long)1 << 33 and higher, not (int)1. Otherwise bad things happen(TM). This is why beast.freebsd.org paniced with ULE. Reviewed by: jeff
2003-12-07 09:57:51 +00:00
if ((rqb->rqb_bits[word] & (1ul << bit)) == 0)
- Add static to local functions and data where it was missing. - Add an IPI based mechanism for migrating kses. This mechanism is broken down into several components. This is intended to reduce cache thrashing by eliminating most cases where one cpu touches another's run queues. - kseq_notify() appends a kse to a lockless singly linked list and conditionally sends an IPI to the target processor. Right now this is protected by sched_lock but at some point I'd like to get rid of the global lock. This is why I used something more complicated than a standard queue. - kseq_assign() processes our list of kses that have been assigned to us by other processors. This simply calls sched_add() for each item on the list after clearing the new KEF_ASSIGNED flag. This flag is used to indicate that we have been appeneded to the assigned queue but not added to the run queue yet. - In sched_add(), instead of adding a KSE to another processor's queue we use kse_notify() so that we don't touch their queue. Also in sched_add(), if KEF_ASSIGNED is already set return immediately. This can happen if a thread is removed and readded so that the priority is recorded properly. - In sched_rem() return immediately if KEF_ASSIGNED is set. All callers immediately readd simply to adjust priorites etc. - In sched_choose(), if we're running an IDLE task or the per cpu idle thread set our cpumask bit in 'kseq_idle' so that other processors may know that we are idle. Before this, make a single pass through the run queues of other processors so that we may find work more immediately if it is available. - In sched_runnable(), don't scan each processor's run queue, they will IPI us if they have work for us to do. - In sched_add(), if we're adding a thread that can be migrated and we have plenty of work to do, try to migrate the thread to an idle kseq. - Simplify the logic in sched_prio() and take the KEF_ASSIGNED flag into consideration. - No longer use kseq_choose() to steal threads, it can lose it's last argument. - Create a new function runq_steal() which operates like runq_choose() but skips threads based on some criteria. Currently it will not steal PRI_ITHD threads. In the future this will be used for CPU binding. - Create a kseq_steal() that checks each run queue with runq_steal(), use kseq_steal() in the places where we used kseq_choose() to steal with before.
2003-10-31 11:16:04 +00:00
continue;
rqh = &rq->rq_queues[bit + (word << RQB_L2BPW)];
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
TAILQ_FOREACH(td, rqh, td_runq)
if (THREAD_CAN_MIGRATE(td) &&
THREAD_CAN_SCHED(td, cpu))
return (td);
- Add static to local functions and data where it was missing. - Add an IPI based mechanism for migrating kses. This mechanism is broken down into several components. This is intended to reduce cache thrashing by eliminating most cases where one cpu touches another's run queues. - kseq_notify() appends a kse to a lockless singly linked list and conditionally sends an IPI to the target processor. Right now this is protected by sched_lock but at some point I'd like to get rid of the global lock. This is why I used something more complicated than a standard queue. - kseq_assign() processes our list of kses that have been assigned to us by other processors. This simply calls sched_add() for each item on the list after clearing the new KEF_ASSIGNED flag. This flag is used to indicate that we have been appeneded to the assigned queue but not added to the run queue yet. - In sched_add(), instead of adding a KSE to another processor's queue we use kse_notify() so that we don't touch their queue. Also in sched_add(), if KEF_ASSIGNED is already set return immediately. This can happen if a thread is removed and readded so that the priority is recorded properly. - In sched_rem() return immediately if KEF_ASSIGNED is set. All callers immediately readd simply to adjust priorites etc. - In sched_choose(), if we're running an IDLE task or the per cpu idle thread set our cpumask bit in 'kseq_idle' so that other processors may know that we are idle. Before this, make a single pass through the run queues of other processors so that we may find work more immediately if it is available. - In sched_runnable(), don't scan each processor's run queue, they will IPI us if they have work for us to do. - In sched_add(), if we're adding a thread that can be migrated and we have plenty of work to do, try to migrate the thread to an idle kseq. - Simplify the logic in sched_prio() and take the KEF_ASSIGNED flag into consideration. - No longer use kseq_choose() to steal threads, it can lose it's last argument. - Create a new function runq_steal() which operates like runq_choose() but skips threads based on some criteria. Currently it will not steal PRI_ITHD threads. In the future this will be used for CPU binding. - Create a kseq_steal() that checks each run queue with runq_steal(), use kseq_steal() in the places where we used kseq_choose() to steal with before.
2003-10-31 11:16:04 +00:00
}
}
return (NULL);
}
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* Attempt to steal a thread in priority order from a thread queue.
*/
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
static struct thread *
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
tdq_steal(struct tdq *tdq, int cpu)
- Add static to local functions and data where it was missing. - Add an IPI based mechanism for migrating kses. This mechanism is broken down into several components. This is intended to reduce cache thrashing by eliminating most cases where one cpu touches another's run queues. - kseq_notify() appends a kse to a lockless singly linked list and conditionally sends an IPI to the target processor. Right now this is protected by sched_lock but at some point I'd like to get rid of the global lock. This is why I used something more complicated than a standard queue. - kseq_assign() processes our list of kses that have been assigned to us by other processors. This simply calls sched_add() for each item on the list after clearing the new KEF_ASSIGNED flag. This flag is used to indicate that we have been appeneded to the assigned queue but not added to the run queue yet. - In sched_add(), instead of adding a KSE to another processor's queue we use kse_notify() so that we don't touch their queue. Also in sched_add(), if KEF_ASSIGNED is already set return immediately. This can happen if a thread is removed and readded so that the priority is recorded properly. - In sched_rem() return immediately if KEF_ASSIGNED is set. All callers immediately readd simply to adjust priorites etc. - In sched_choose(), if we're running an IDLE task or the per cpu idle thread set our cpumask bit in 'kseq_idle' so that other processors may know that we are idle. Before this, make a single pass through the run queues of other processors so that we may find work more immediately if it is available. - In sched_runnable(), don't scan each processor's run queue, they will IPI us if they have work for us to do. - In sched_add(), if we're adding a thread that can be migrated and we have plenty of work to do, try to migrate the thread to an idle kseq. - Simplify the logic in sched_prio() and take the KEF_ASSIGNED flag into consideration. - No longer use kseq_choose() to steal threads, it can lose it's last argument. - Create a new function runq_steal() which operates like runq_choose() but skips threads based on some criteria. Currently it will not steal PRI_ITHD threads. In the future this will be used for CPU binding. - Create a kseq_steal() that checks each run queue with runq_steal(), use kseq_steal() in the places where we used kseq_choose() to steal with before.
2003-10-31 11:16:04 +00:00
{
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
struct thread *td;
- Add static to local functions and data where it was missing. - Add an IPI based mechanism for migrating kses. This mechanism is broken down into several components. This is intended to reduce cache thrashing by eliminating most cases where one cpu touches another's run queues. - kseq_notify() appends a kse to a lockless singly linked list and conditionally sends an IPI to the target processor. Right now this is protected by sched_lock but at some point I'd like to get rid of the global lock. This is why I used something more complicated than a standard queue. - kseq_assign() processes our list of kses that have been assigned to us by other processors. This simply calls sched_add() for each item on the list after clearing the new KEF_ASSIGNED flag. This flag is used to indicate that we have been appeneded to the assigned queue but not added to the run queue yet. - In sched_add(), instead of adding a KSE to another processor's queue we use kse_notify() so that we don't touch their queue. Also in sched_add(), if KEF_ASSIGNED is already set return immediately. This can happen if a thread is removed and readded so that the priority is recorded properly. - In sched_rem() return immediately if KEF_ASSIGNED is set. All callers immediately readd simply to adjust priorites etc. - In sched_choose(), if we're running an IDLE task or the per cpu idle thread set our cpumask bit in 'kseq_idle' so that other processors may know that we are idle. Before this, make a single pass through the run queues of other processors so that we may find work more immediately if it is available. - In sched_runnable(), don't scan each processor's run queue, they will IPI us if they have work for us to do. - In sched_add(), if we're adding a thread that can be migrated and we have plenty of work to do, try to migrate the thread to an idle kseq. - Simplify the logic in sched_prio() and take the KEF_ASSIGNED flag into consideration. - No longer use kseq_choose() to steal threads, it can lose it's last argument. - Create a new function runq_steal() which operates like runq_choose() but skips threads based on some criteria. Currently it will not steal PRI_ITHD threads. In the future this will be used for CPU binding. - Create a kseq_steal() that checks each run queue with runq_steal(), use kseq_steal() in the places where we used kseq_choose() to steal with before.
2003-10-31 11:16:04 +00:00
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
if ((td = runq_steal(&tdq->tdq_realtime, cpu)) != NULL)
return (td);
if ((td = runq_steal_from(&tdq->tdq_timeshare,
cpu, tdq->tdq_ridx)) != NULL)
return (td);
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
return (runq_steal(&tdq->tdq_idle, cpu));
- Add support for CPU groups to ule. All SMT cores on the same physical cpu are added to a group. - Don't place a cpu into the kseq_idle bitmask until all cpus in that group have idled. - Prefer idle groups over idle group members in the new kseq_transfer() function. In this way we will prefer to balance load across full cores rather than add further load a partial core. - Before a cpu goes idle, check the other group members for threads. Since SMT cpus may freely share threads, this is cheap. - SMT cores may be individually pinned and bound to now. This contrasts the old mechanism where binding or pinning would have allowed a thread to run on any available cpu. - Remove some unnecessary logic from sched_switch(). Priority propagation should be properly taken care of in sched_prio() now.
2003-12-11 03:57:10 +00:00
}
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* Sets the thread lock and ts_cpu to match the requested cpu. Unlocks the
- Move the rebalancer back into hardclock to prevent potential softclock starvation caused by unbalanced interrupt loads. - Change the rebalancer to work on stathz ticks but retain randomization. - Simplify locking in tdq_idled() to use the tdq_lock_pair() rather than complex sequences of locks to avoid deadlock. Reported by: kris Approved by: re
2007-10-02 00:36:06 +00:00
* current lock and returns with the assigned queue locked.
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
*/
static inline struct tdq *
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
sched_setcpu(struct thread *td, int cpu, int flags)
- Add support for CPU groups to ule. All SMT cores on the same physical cpu are added to a group. - Don't place a cpu into the kseq_idle bitmask until all cpus in that group have idled. - Prefer idle groups over idle group members in the new kseq_transfer() function. In this way we will prefer to balance load across full cores rather than add further load a partial core. - Before a cpu goes idle, check the other group members for threads. Since SMT cpus may freely share threads, this is cheap. - SMT cores may be individually pinned and bound to now. This contrasts the old mechanism where binding or pinning would have allowed a thread to run on any available cpu. - Remove some unnecessary logic from sched_switch(). Priority propagation should be properly taken care of in sched_prio() now.
2003-12-11 03:57:10 +00:00
{
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
struct tdq *tdq;
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
THREAD_LOCK_ASSERT(td, MA_OWNED);
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
tdq = TDQ_CPU(cpu);
Get rid of struct proc p_sched and struct thread td_sched pointers. p_sched is unused. The struct td_sched is always co-allocated with the struct thread, except for the thread0. Avoid useless indirection, instead calculate td_sched location using simple pointer arithmetic in td_get_sched(9). For thread0, which is statically allocated, create a structure to emulate layout of the dynamic allocation. Reviewed by: jhb (previous version) Sponsored by: The FreeBSD Foundation Differential revision: https://reviews.freebsd.org/D6711
2016-06-05 17:04:03 +00:00
td_get_sched(td)->ts_cpu = cpu;
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
/*
* If the lock matches just return the queue.
*/
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
if (td->td_lock == TDQ_LOCKPTR(tdq))
return (tdq);
#ifdef notyet
Major revamp of ULE's cpu load balancing: - Switch back to direct modification of remote CPU run queues. This added a lot of complexity with questionable gain. It's easy enough to reimplement if it's shown to help on huge machines. - Re-implement the old tdq_transfer() call as tdq_pickidle(). Change sched_add() so we have selectable cpu choosers and simplify the logic a bit here. - Implement tdq_pickpri() as the new default cpu chooser. This algorithm is similar to Solaris in that it tries to always run the threads with the best priorities. It is actually slightly more complex than solaris's algorithm because we also tend to favor the local cpu over other cpus which has a boost in latency but also potentially enables cache sharing between the waking thread and the woken thread. - Add a bunch of tunables that can be used to measure effects of different load balancing strategies. Most of these will go away once the algorithm is more definite. - Add a new mechanism to steal threads from busy cpus when we idle. This is enabled with kern.sched.steal_busy and kern.sched.busy_thresh. The threshold is the required length of a tdq's run queue before another cpu will be able to steal runnable threads. This prevents most queue imbalances that contribute the long latencies.
2007-01-19 21:56:08 +00:00
/*
- Improve grammar. s/it's/its/. - Improve load long-term load balancer by always IPIing exactly once. Previously the delay after rebalancing could cause problems with uneven workloads. - Allow nice to have a linear effect on the interactivity score. This allows negatively niced programs to stay interactive longer. It may be useful with very expensive Xorg servers under high loads. In general it should not be necessary to alter the nice level to improve interactive response. We may also want to consider never allowing positively niced processes to become interactive at all. - Initialize ccpu to 0 rather than 0.0. The decimal point was leftover from when the code was copied from 4bsd. ccpu is 0 in ULE because ULE only exports weighted cpu values. Reported by: Steve Kargl (Load balancing problem) Approved by: re
2007-09-22 02:20:14 +00:00
* If the thread isn't running its lockptr is a
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
* turnstile or a sleepqueue. We can just lock_set without
* blocking.
Major revamp of ULE's cpu load balancing: - Switch back to direct modification of remote CPU run queues. This added a lot of complexity with questionable gain. It's easy enough to reimplement if it's shown to help on huge machines. - Re-implement the old tdq_transfer() call as tdq_pickidle(). Change sched_add() so we have selectable cpu choosers and simplify the logic a bit here. - Implement tdq_pickpri() as the new default cpu chooser. This algorithm is similar to Solaris in that it tries to always run the threads with the best priorities. It is actually slightly more complex than solaris's algorithm because we also tend to favor the local cpu over other cpus which has a boost in latency but also potentially enables cache sharing between the waking thread and the woken thread. - Add a bunch of tunables that can be used to measure effects of different load balancing strategies. Most of these will go away once the algorithm is more definite. - Add a new mechanism to steal threads from busy cpus when we idle. This is enabled with kern.sched.steal_busy and kern.sched.busy_thresh. The threshold is the required length of a tdq's run queue before another cpu will be able to steal runnable threads. This prevents most queue imbalances that contribute the long latencies.
2007-01-19 21:56:08 +00:00
*/
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
if (TD_CAN_RUN(td)) {
TDQ_LOCK(tdq);
thread_lock_set(td, TDQ_LOCKPTR(tdq));
return (tdq);
}
#endif
Major revamp of ULE's cpu load balancing: - Switch back to direct modification of remote CPU run queues. This added a lot of complexity with questionable gain. It's easy enough to reimplement if it's shown to help on huge machines. - Re-implement the old tdq_transfer() call as tdq_pickidle(). Change sched_add() so we have selectable cpu choosers and simplify the logic a bit here. - Implement tdq_pickpri() as the new default cpu chooser. This algorithm is similar to Solaris in that it tries to always run the threads with the best priorities. It is actually slightly more complex than solaris's algorithm because we also tend to favor the local cpu over other cpus which has a boost in latency but also potentially enables cache sharing between the waking thread and the woken thread. - Add a bunch of tunables that can be used to measure effects of different load balancing strategies. Most of these will go away once the algorithm is more definite. - Add a new mechanism to steal threads from busy cpus when we idle. This is enabled with kern.sched.steal_busy and kern.sched.busy_thresh. The threshold is the required length of a tdq's run queue before another cpu will be able to steal runnable threads. This prevents most queue imbalances that contribute the long latencies.
2007-01-19 21:56:08 +00:00
/*
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
* The hard case, migration, we need to block the thread first to
* prevent order reversals with other cpus locks.
Major revamp of ULE's cpu load balancing: - Switch back to direct modification of remote CPU run queues. This added a lot of complexity with questionable gain. It's easy enough to reimplement if it's shown to help on huge machines. - Re-implement the old tdq_transfer() call as tdq_pickidle(). Change sched_add() so we have selectable cpu choosers and simplify the logic a bit here. - Implement tdq_pickpri() as the new default cpu chooser. This algorithm is similar to Solaris in that it tries to always run the threads with the best priorities. It is actually slightly more complex than solaris's algorithm because we also tend to favor the local cpu over other cpus which has a boost in latency but also potentially enables cache sharing between the waking thread and the woken thread. - Add a bunch of tunables that can be used to measure effects of different load balancing strategies. Most of these will go away once the algorithm is more definite. - Add a new mechanism to steal threads from busy cpus when we idle. This is enabled with kern.sched.steal_busy and kern.sched.busy_thresh. The threshold is the required length of a tdq's run queue before another cpu will be able to steal runnable threads. This prevents most queue imbalances that contribute the long latencies.
2007-01-19 21:56:08 +00:00
*/
- Fix a race in sched_switch() of sched_4bsd. In the case of the thread being on a sleepqueue or a turnstile, the sched_lock was acquired (without the aid of the td_lock interface) and the td_lock was dropped. This was going to break locking rules on other threads willing to access to the thread (via the td_lock interface) and modify his flags (allowed as long as the container lock was different by the one used in sched_switch). In order to prevent this situation, while sched_lock is acquired there the td_lock gets blocked. [0] - Merge the ULE's internal function thread_block_switch() into the global thread_lock_block() and make the former semantic as the default for thread_lock_block(). This means that thread_lock_block() will not disable interrupts when called (and consequently thread_unlock_block() will not re-enabled them when called). This should be done manually when necessary. Note, however, that ULE's thread_unblock_switch() is not reaped because it does reflect a difference in semantic due in ULE (the td_lock may not be necessarilly still blocked_lock when calling this). While asymmetric, it does describe a remarkable difference in semantic that is good to keep in mind. [0] Reported by: Kohji Okuno <okuno dot kohji at jp dot panasonic dot com> Tested by: Giovanni Trematerra <giovanni dot trematerra at gmail dot com> MFC: 2 weeks
2010-01-23 15:54:21 +00:00
spinlock_enter();
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
thread_lock_block(td);
TDQ_LOCK(tdq);
- Share scheduler locks between hyper-threaded cores to protect the tdq_group structure. Hyper-threaded cores won't really benefit from seperate locks anyway. - Seperate out the migration case from sched_switch to simplify the main switch code. We only migrate here if called via sched_bind(). - When preempted place the preempted thread back in the same queue at the head. - Improve the cpu group and topology infrastructure. Tested by: many on current@ Approved by: re
2007-08-03 23:38:46 +00:00
thread_lock_unblock(td, TDQ_LOCKPTR(tdq));
- Fix a race in sched_switch() of sched_4bsd. In the case of the thread being on a sleepqueue or a turnstile, the sched_lock was acquired (without the aid of the td_lock interface) and the td_lock was dropped. This was going to break locking rules on other threads willing to access to the thread (via the td_lock interface) and modify his flags (allowed as long as the container lock was different by the one used in sched_switch). In order to prevent this situation, while sched_lock is acquired there the td_lock gets blocked. [0] - Merge the ULE's internal function thread_block_switch() into the global thread_lock_block() and make the former semantic as the default for thread_lock_block(). This means that thread_lock_block() will not disable interrupts when called (and consequently thread_unlock_block() will not re-enabled them when called). This should be done manually when necessary. Note, however, that ULE's thread_unblock_switch() is not reaped because it does reflect a difference in semantic due in ULE (the td_lock may not be necessarilly still blocked_lock when calling this). While asymmetric, it does describe a remarkable difference in semantic that is good to keep in mind. [0] Reported by: Kohji Okuno <okuno dot kohji at jp dot panasonic dot com> Tested by: Giovanni Trematerra <giovanni dot trematerra at gmail dot com> MFC: 2 weeks
2010-01-23 15:54:21 +00:00
spinlock_exit();
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
return (tdq);
Major revamp of ULE's cpu load balancing: - Switch back to direct modification of remote CPU run queues. This added a lot of complexity with questionable gain. It's easy enough to reimplement if it's shown to help on huge machines. - Re-implement the old tdq_transfer() call as tdq_pickidle(). Change sched_add() so we have selectable cpu choosers and simplify the logic a bit here. - Implement tdq_pickpri() as the new default cpu chooser. This algorithm is similar to Solaris in that it tries to always run the threads with the best priorities. It is actually slightly more complex than solaris's algorithm because we also tend to favor the local cpu over other cpus which has a boost in latency but also potentially enables cache sharing between the waking thread and the woken thread. - Add a bunch of tunables that can be used to measure effects of different load balancing strategies. Most of these will go away once the algorithm is more definite. - Add a new mechanism to steal threads from busy cpus when we idle. This is enabled with kern.sched.steal_busy and kern.sched.busy_thresh. The threshold is the required length of a tdq's run queue before another cpu will be able to steal runnable threads. This prevents most queue imbalances that contribute the long latencies.
2007-01-19 21:56:08 +00:00
}
- Make SCHED_STATS more generic by adding a wrapper to create the variables and sysctl nodes. - In reset walk the children of kern_sched_stats and reset the counters via the oid_arg1 pointer. This allows us to add arbitrary counters to the tree and still reset them properly. - Define a set of switch types to be passed with flags to mi_switch(). These types are named SWT_*. These types correspond to SCHED_STATS counters and are automatically handled in this way. - Make the new SWT_ types more specific than the older switch stats. There are now stats for idle switches, remote idle wakeups, remote preemption ithreads idling, etc. - Add switch statistics for ULE's pickcpu algorithm. These stats include how much migration there is, how often affinity was successful, how often threads were migrated to the local cpu on wakeup, etc. Sponsored by: Nokia
2008-04-17 04:20:10 +00:00
SCHED_STAT_DEFINE(pickcpu_intrbind, "Soft interrupt binding");
SCHED_STAT_DEFINE(pickcpu_idle_affinity, "Picked idle cpu based on affinity");
SCHED_STAT_DEFINE(pickcpu_affinity, "Picked cpu based on affinity");
SCHED_STAT_DEFINE(pickcpu_lowest, "Selected lowest load");
SCHED_STAT_DEFINE(pickcpu_local, "Migrated to current cpu");
SCHED_STAT_DEFINE(pickcpu_migration, "Selection may have caused migration");
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
static int
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
sched_pickcpu(struct thread *td, int flags)
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
{
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
struct cpu_group *cg, *ccg;
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
struct td_sched *ts;
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
struct tdq *tdq;
- Use cpuset_t and the CPU_ macros in place of cpumask_t so that ULE supports arbitrary numbers of cpus rather than being limited by cpumask_t to the number of bits in a long.
2009-06-23 22:12:37 +00:00
cpuset_t mask;
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
int cpu, pri, self;
Major revamp of ULE's cpu load balancing: - Switch back to direct modification of remote CPU run queues. This added a lot of complexity with questionable gain. It's easy enough to reimplement if it's shown to help on huge machines. - Re-implement the old tdq_transfer() call as tdq_pickidle(). Change sched_add() so we have selectable cpu choosers and simplify the logic a bit here. - Implement tdq_pickpri() as the new default cpu chooser. This algorithm is similar to Solaris in that it tries to always run the threads with the best priorities. It is actually slightly more complex than solaris's algorithm because we also tend to favor the local cpu over other cpus which has a boost in latency but also potentially enables cache sharing between the waking thread and the woken thread. - Add a bunch of tunables that can be used to measure effects of different load balancing strategies. Most of these will go away once the algorithm is more definite. - Add a new mechanism to steal threads from busy cpus when we idle. This is enabled with kern.sched.steal_busy and kern.sched.busy_thresh. The threshold is the required length of a tdq's run queue before another cpu will be able to steal runnable threads. This prevents most queue imbalances that contribute the long latencies.
2007-01-19 21:56:08 +00:00
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
self = PCPU_GET(cpuid);
Get rid of struct proc p_sched and struct thread td_sched pointers. p_sched is unused. The struct td_sched is always co-allocated with the struct thread, except for the thread0. Avoid useless indirection, instead calculate td_sched location using simple pointer arithmetic in td_get_sched(9). For thread0, which is statically allocated, create a structure to emulate layout of the dynamic allocation. Reviewed by: jhb (previous version) Sponsored by: The FreeBSD Foundation Differential revision: https://reviews.freebsd.org/D6711
2016-06-05 17:04:03 +00:00
ts = td_get_sched(td);
Remove some, but not all, assumptions that the BSP is CPU 0 and that CPUs are numbered densely from there to n_cpus. MFC after: 1 month
2017-11-25 23:41:05 +00:00
KASSERT(!CPU_ABSENT(ts->ts_cpu), ("sched_pickcpu: Start scheduler on "
"absent CPU %d for thread %s.", ts->ts_cpu, td->td_name));
Major revamp of ULE's cpu load balancing: - Switch back to direct modification of remote CPU run queues. This added a lot of complexity with questionable gain. It's easy enough to reimplement if it's shown to help on huge machines. - Re-implement the old tdq_transfer() call as tdq_pickidle(). Change sched_add() so we have selectable cpu choosers and simplify the logic a bit here. - Implement tdq_pickpri() as the new default cpu chooser. This algorithm is similar to Solaris in that it tries to always run the threads with the best priorities. It is actually slightly more complex than solaris's algorithm because we also tend to favor the local cpu over other cpus which has a boost in latency but also potentially enables cache sharing between the waking thread and the woken thread. - Add a bunch of tunables that can be used to measure effects of different load balancing strategies. Most of these will go away once the algorithm is more definite. - Add a new mechanism to steal threads from busy cpus when we idle. This is enabled with kern.sched.steal_busy and kern.sched.busy_thresh. The threshold is the required length of a tdq's run queue before another cpu will be able to steal runnable threads. This prevents most queue imbalances that contribute the long latencies.
2007-01-19 21:56:08 +00:00
if (smp_started == 0)
return (self);
- Refine the load balancer to improve buildkernel times on dual core machines. - Leave the long-term load balancer running by default once per second. - Enable stealing load from the idle thread only when the remote processor has more than two transferable tasks. Setting this to one further improves buildworld. Setting it higher improves mysql. - Remove the bogus pick_zero option. I had not intended to commit this. - Entirely disallow migration for threads with SRQ_YIELDING set. This balances out the extra migration allowed for with the load balancers. It also makes pick_pri perform better as I had anticipated. Tested by: Dmitry Morozovsky <marck@rinet.ru> Approved by: re
2007-07-19 20:03:15 +00:00
/*
* Don't migrate a running thread from sched_switch().
*/
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
if ((flags & SRQ_OURSELF) || !THREAD_CAN_MIGRATE(td))
return (ts->ts_cpu);
Major revamp of ULE's cpu load balancing: - Switch back to direct modification of remote CPU run queues. This added a lot of complexity with questionable gain. It's easy enough to reimplement if it's shown to help on huge machines. - Re-implement the old tdq_transfer() call as tdq_pickidle(). Change sched_add() so we have selectable cpu choosers and simplify the logic a bit here. - Implement tdq_pickpri() as the new default cpu chooser. This algorithm is similar to Solaris in that it tries to always run the threads with the best priorities. It is actually slightly more complex than solaris's algorithm because we also tend to favor the local cpu over other cpus which has a boost in latency but also potentially enables cache sharing between the waking thread and the woken thread. - Add a bunch of tunables that can be used to measure effects of different load balancing strategies. Most of these will go away once the algorithm is more definite. - Add a new mechanism to steal threads from busy cpus when we idle. This is enabled with kern.sched.steal_busy and kern.sched.busy_thresh. The threshold is the required length of a tdq's run queue before another cpu will be able to steal runnable threads. This prevents most queue imbalances that contribute the long latencies.
2007-01-19 21:56:08 +00:00
/*
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
* Prefer to run interrupt threads on the processors that generate
* the interrupt.
Major revamp of ULE's cpu load balancing: - Switch back to direct modification of remote CPU run queues. This added a lot of complexity with questionable gain. It's easy enough to reimplement if it's shown to help on huge machines. - Re-implement the old tdq_transfer() call as tdq_pickidle(). Change sched_add() so we have selectable cpu choosers and simplify the logic a bit here. - Implement tdq_pickpri() as the new default cpu chooser. This algorithm is similar to Solaris in that it tries to always run the threads with the best priorities. It is actually slightly more complex than solaris's algorithm because we also tend to favor the local cpu over other cpus which has a boost in latency but also potentially enables cache sharing between the waking thread and the woken thread. - Add a bunch of tunables that can be used to measure effects of different load balancing strategies. Most of these will go away once the algorithm is more definite. - Add a new mechanism to steal threads from busy cpus when we idle. This is enabled with kern.sched.steal_busy and kern.sched.busy_thresh. The threshold is the required length of a tdq's run queue before another cpu will be able to steal runnable threads. This prevents most queue imbalances that contribute the long latencies.
2007-01-19 21:56:08 +00:00
*/
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
pri = td->td_priority;
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
if (td->td_priority <= PRI_MAX_ITHD && THREAD_CAN_SCHED(td, self) &&
- Make SCHED_STATS more generic by adding a wrapper to create the variables and sysctl nodes. - In reset walk the children of kern_sched_stats and reset the counters via the oid_arg1 pointer. This allows us to add arbitrary counters to the tree and still reset them properly. - Define a set of switch types to be passed with flags to mi_switch(). These types are named SWT_*. These types correspond to SCHED_STATS counters and are automatically handled in this way. - Make the new SWT_ types more specific than the older switch stats. There are now stats for idle switches, remote idle wakeups, remote preemption ithreads idling, etc. - Add switch statistics for ULE's pickcpu algorithm. These stats include how much migration there is, how often affinity was successful, how often threads were migrated to the local cpu on wakeup, etc. Sponsored by: Nokia
2008-04-17 04:20:10 +00:00
curthread->td_intr_nesting_level && ts->ts_cpu != self) {
SCHED_STAT_INC(pickcpu_intrbind);
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
ts->ts_cpu = self;
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
if (TDQ_CPU(self)->tdq_lowpri > pri) {
SCHED_STAT_INC(pickcpu_affinity);
return (ts->ts_cpu);
}
- Make SCHED_STATS more generic by adding a wrapper to create the variables and sysctl nodes. - In reset walk the children of kern_sched_stats and reset the counters via the oid_arg1 pointer. This allows us to add arbitrary counters to the tree and still reset them properly. - Define a set of switch types to be passed with flags to mi_switch(). These types are named SWT_*. These types correspond to SCHED_STATS counters and are automatically handled in this way. - Make the new SWT_ types more specific than the older switch stats. There are now stats for idle switches, remote idle wakeups, remote preemption ithreads idling, etc. - Add switch statistics for ULE's pickcpu algorithm. These stats include how much migration there is, how often affinity was successful, how often threads were migrated to the local cpu on wakeup, etc. Sponsored by: Nokia
2008-04-17 04:20:10 +00:00
}
Major revamp of ULE's cpu load balancing: - Switch back to direct modification of remote CPU run queues. This added a lot of complexity with questionable gain. It's easy enough to reimplement if it's shown to help on huge machines. - Re-implement the old tdq_transfer() call as tdq_pickidle(). Change sched_add() so we have selectable cpu choosers and simplify the logic a bit here. - Implement tdq_pickpri() as the new default cpu chooser. This algorithm is similar to Solaris in that it tries to always run the threads with the best priorities. It is actually slightly more complex than solaris's algorithm because we also tend to favor the local cpu over other cpus which has a boost in latency but also potentially enables cache sharing between the waking thread and the woken thread. - Add a bunch of tunables that can be used to measure effects of different load balancing strategies. Most of these will go away once the algorithm is more definite. - Add a new mechanism to steal threads from busy cpus when we idle. This is enabled with kern.sched.steal_busy and kern.sched.busy_thresh. The threshold is the required length of a tdq's run queue before another cpu will be able to steal runnable threads. This prevents most queue imbalances that contribute the long latencies.
2007-01-19 21:56:08 +00:00
/*
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
* If the thread can run on the last cpu and the affinity has not
sched_ule: update a comment to reflect reality MFC after: 3 days Sponsored by: Dell EMC
2018-02-22 17:09:26 +00:00
* expired and it is idle, run it there.
Major revamp of ULE's cpu load balancing: - Switch back to direct modification of remote CPU run queues. This added a lot of complexity with questionable gain. It's easy enough to reimplement if it's shown to help on huge machines. - Re-implement the old tdq_transfer() call as tdq_pickidle(). Change sched_add() so we have selectable cpu choosers and simplify the logic a bit here. - Implement tdq_pickpri() as the new default cpu chooser. This algorithm is similar to Solaris in that it tries to always run the threads with the best priorities. It is actually slightly more complex than solaris's algorithm because we also tend to favor the local cpu over other cpus which has a boost in latency but also potentially enables cache sharing between the waking thread and the woken thread. - Add a bunch of tunables that can be used to measure effects of different load balancing strategies. Most of these will go away once the algorithm is more definite. - Add a new mechanism to steal threads from busy cpus when we idle. This is enabled with kern.sched.steal_busy and kern.sched.busy_thresh. The threshold is the required length of a tdq's run queue before another cpu will be able to steal runnable threads. This prevents most queue imbalances that contribute the long latencies.
2007-01-19 21:56:08 +00:00
*/
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
tdq = TDQ_CPU(ts->ts_cpu);
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
cg = tdq->tdq_cg;
if (THREAD_CAN_SCHED(td, ts->ts_cpu) &&
tdq->tdq_lowpri >= PRI_MIN_IDLE &&
SCHED_AFFINITY(ts, CG_SHARE_L2)) {
if (cg->cg_flags & CG_FLAG_THREAD) {
CPUSET_FOREACH(cpu, cg->cg_mask) {
if (TDQ_CPU(cpu)->tdq_lowpri < PRI_MIN_IDLE)
break;
}
} else
cpu = INT_MAX;
if (cpu > mp_maxid) {
- Make SCHED_STATS more generic by adding a wrapper to create the variables and sysctl nodes. - In reset walk the children of kern_sched_stats and reset the counters via the oid_arg1 pointer. This allows us to add arbitrary counters to the tree and still reset them properly. - Define a set of switch types to be passed with flags to mi_switch(). These types are named SWT_*. These types correspond to SCHED_STATS counters and are automatically handled in this way. - Make the new SWT_ types more specific than the older switch stats. There are now stats for idle switches, remote idle wakeups, remote preemption ithreads idling, etc. - Add switch statistics for ULE's pickcpu algorithm. These stats include how much migration there is, how often affinity was successful, how often threads were migrated to the local cpu on wakeup, etc. Sponsored by: Nokia
2008-04-17 04:20:10 +00:00
SCHED_STAT_INC(pickcpu_idle_affinity);
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
return (ts->ts_cpu);
- Make SCHED_STATS more generic by adding a wrapper to create the variables and sysctl nodes. - In reset walk the children of kern_sched_stats and reset the counters via the oid_arg1 pointer. This allows us to add arbitrary counters to the tree and still reset them properly. - Define a set of switch types to be passed with flags to mi_switch(). These types are named SWT_*. These types correspond to SCHED_STATS counters and are automatically handled in this way. - Make the new SWT_ types more specific than the older switch stats. There are now stats for idle switches, remote idle wakeups, remote preemption ithreads idling, etc. - Add switch statistics for ULE's pickcpu algorithm. These stats include how much migration there is, how often affinity was successful, how often threads were migrated to the local cpu on wakeup, etc. Sponsored by: Nokia
2008-04-17 04:20:10 +00:00
}
- Fix a long standing problem where an ithread would not honor sched_pin(). - Remove the sched_add wrapper that used sched_add_internal() as a backend. Its only purpose was to interpret one flag and turn it into an int. Do the right thing and interpret the flag in sched_add() instead. - Pass the flag argument to sched_add() to kseq_runq_add() so that we can get the SRQ_PREEMPT optimization too. - Add a KEF_INTERNAL flag. If KEF_INTERNAL is set we don't adjust the SLOT counts, otherwise the slot counts are adjusted as soon as we enter sched_add() or sched_rem() rather than when the thread is actually placed on the run queue. This greatly simplifies the handling of slots. - Remove the explicit prevention of migration for ithreads on non-x86 platforms. This was never shown to have any real benefit. - Remove the unused class argument to KSE_CAN_MIGRATE(). - Add ktr points for thread migration events. - Fix a long standing bug on platforms which don't initialize the cpu topology. The ksg_maxid variable was never correctly set on these platforms which caused the long term load balancer to never inspect more than the first group or processor. - Fix another bug which prevented the long term load balancer from working properly. If stathz != hz we can't expect sched_clock() to be called on the exact tick count that we're anticipating. - Rearrange sched_switch() a bit to reduce indentation levels.
2004-12-26 22:56:08 +00:00
}
- Add support for CPU groups to ule. All SMT cores on the same physical cpu are added to a group. - Don't place a cpu into the kseq_idle bitmask until all cpus in that group have idled. - Prefer idle groups over idle group members in the new kseq_transfer() function. In this way we will prefer to balance load across full cores rather than add further load a partial core. - Before a cpu goes idle, check the other group members for threads. Since SMT cpus may freely share threads, this is cheap. - SMT cores may be individually pinned and bound to now. This contrasts the old mechanism where binding or pinning would have allowed a thread to run on any available cpu. - Remove some unnecessary logic from sched_switch(). Priority propagation should be properly taken care of in sched_prio() now.
2003-12-11 03:57:10 +00:00
/*
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
* Search for the last level cache CPU group in the tree.
* Skip caches with expired affinity time and SMT groups.
* Affinity to higher level caches will be handled less aggressively.
- Add support for CPU groups to ule. All SMT cores on the same physical cpu are added to a group. - Don't place a cpu into the kseq_idle bitmask until all cpus in that group have idled. - Prefer idle groups over idle group members in the new kseq_transfer() function. In this way we will prefer to balance load across full cores rather than add further load a partial core. - Before a cpu goes idle, check the other group members for threads. Since SMT cpus may freely share threads, this is cheap. - SMT cores may be individually pinned and bound to now. This contrasts the old mechanism where binding or pinning would have allowed a thread to run on any available cpu. - Remove some unnecessary logic from sched_switch(). Priority propagation should be properly taken care of in sched_prio() now.
2003-12-11 03:57:10 +00:00
*/
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
for (ccg = NULL; cg != NULL; cg = cg->cg_parent) {
if (cg->cg_flags & CG_FLAG_THREAD)
continue;
if (!SCHED_AFFINITY(ts, cg->cg_level))
continue;
ccg = cg;
}
if (ccg != NULL)
cg = ccg;
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
cpu = -1;
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
/* Search the group for the less loaded idle CPU we can run now. */
- Use cpuset_t and the CPU_ macros in place of cpumask_t so that ULE supports arbitrary numbers of cpus rather than being limited by cpumask_t to the number of bits in a long.
2009-06-23 22:12:37 +00:00
mask = td->td_cpuset->cs_mask;
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
if (cg != NULL && cg != cpu_top &&
CPU_CMP(&cg->cg_mask, &cpu_top->cg_mask) != 0)
cpu = sched_lowest(cg, mask, max(pri, PRI_MAX_TIMESHARE),
INT_MAX, ts->ts_cpu);
/* Search globally for the less loaded CPU we can run now. */
if (cpu == -1)
cpu = sched_lowest(cpu_top, mask, pri, INT_MAX, ts->ts_cpu);
/* Search globally for the less loaded CPU. */
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
if (cpu == -1)
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
cpu = sched_lowest(cpu_top, mask, -1, INT_MAX, ts->ts_cpu);
Fix bug of r232207, when cpu_search() could prefer CPU group with best load, but with no CPU matching given limitations. It caused kernel panics in some cases when thread was bound to specific CPUs with cpuset(1).
2012-03-03 11:50:48 +00:00
KASSERT(cpu != -1, ("sched_pickcpu: Failed to find a cpu."));
Remove some, but not all, assumptions that the BSP is CPU 0 and that CPUs are numbered densely from there to n_cpus. MFC after: 1 month
2017-11-25 23:41:05 +00:00
KASSERT(!CPU_ABSENT(cpu), ("sched_pickcpu: Picked absent CPU %d.", cpu));
- Refine the load balancer to improve buildkernel times on dual core machines. - Leave the long-term load balancer running by default once per second. - Enable stealing load from the idle thread only when the remote processor has more than two transferable tasks. Setting this to one further improves buildworld. Setting it higher improves mysql. - Remove the bogus pick_zero option. I had not intended to commit this. - Entirely disallow migration for threads with SRQ_YIELDING set. This balances out the extra migration allowed for with the load balancers. It also makes pick_pri perform better as I had anticipated. Tested by: Dmitry Morozovsky <marck@rinet.ru> Approved by: re
2007-07-19 20:03:15 +00:00
/*
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
* Compare the lowest loaded cpu to current cpu.
- Refine the load balancer to improve buildkernel times on dual core machines. - Leave the long-term load balancer running by default once per second. - Enable stealing load from the idle thread only when the remote processor has more than two transferable tasks. Setting this to one further improves buildworld. Setting it higher improves mysql. - Remove the bogus pick_zero option. I had not intended to commit this. - Entirely disallow migration for threads with SRQ_YIELDING set. This balances out the extra migration allowed for with the load balancers. It also makes pick_pri perform better as I had anticipated. Tested by: Dmitry Morozovsky <marck@rinet.ru> Approved by: re
2007-07-19 20:03:15 +00:00
*/
- Add an implementation of sched_preempt() that avoids excessive IPIs. - Normalize the preemption/ipi setting code by introducing sched_shouldpreempt() so the logical is identical and not repeated between tdq_notify() and sched_setpreempt(). - In tdq_notify() don't set NEEDRESCHED as we may not actually own the thread lock this could have caused us to lose td_flags settings. - Garbage collect some tunables that are no longer relevant.
2008-03-10 01:32:01 +00:00
if (THREAD_CAN_SCHED(td, self) && TDQ_CPU(self)->tdq_lowpri > pri &&
Rework CPU load balancing in SCHED_ULE: - In sched_pickcpu() be more careful taking previous CPU on SMT systems. Do it only if all other logical CPUs of that physical one are idle to avoid extra resource sharing. - In sched_pickcpu() change general logic of CPU selection. First look for idle CPU, sharing last level cache with previously used one, skipping SMT CPU groups. If none found, search all CPUs for the least loaded one, where the thread with its priority can run now. If none found, search just for the least loaded CPU. - Make cpu_search() compare lowest/highest CPU load when comparing CPU groups with equal load. That allows to differentiate 1+1 and 2+0 loads. - Make cpu_search() to prefer specified (previous) CPU or group if load is equal. This improves cache affinity for more complicated topologies. - Randomize CPU selection if above factors are equal. Previous code tend to prefer CPUs with lower IDs, causing unneeded collisions. - Rework periodic balancer in sched_balance_group(). With cpu_search() more intelligent now, make balansing process flat, removing recursion over the topology tree. That fixes double swap problem and makes load distribution more even and predictable. All together this gives 10-15% performance improvement in many tests on CPUs with SMT, such as Core i7, for number of threads is less then number of logical CPUs. In some tests it also gives positive effect to systems without SMT. Reviewed by: jeff Tested by: flo, hackers@ MFC after: 1 month Sponsored by: iXsystems, Inc.
2012-02-27 10:31:54 +00:00
TDQ_CPU(cpu)->tdq_lowpri < PRI_MIN_IDLE &&
TDQ_CPU(self)->tdq_load <= TDQ_CPU(cpu)->tdq_load + 1) {
- Make SCHED_STATS more generic by adding a wrapper to create the variables and sysctl nodes. - In reset walk the children of kern_sched_stats and reset the counters via the oid_arg1 pointer. This allows us to add arbitrary counters to the tree and still reset them properly. - Define a set of switch types to be passed with flags to mi_switch(). These types are named SWT_*. These types correspond to SCHED_STATS counters and are automatically handled in this way. - Make the new SWT_ types more specific than the older switch stats. There are now stats for idle switches, remote idle wakeups, remote preemption ithreads idling, etc. - Add switch statistics for ULE's pickcpu algorithm. These stats include how much migration there is, how often affinity was successful, how often threads were migrated to the local cpu on wakeup, etc. Sponsored by: Nokia
2008-04-17 04:20:10 +00:00
SCHED_STAT_INC(pickcpu_local);
- Add an implementation of sched_preempt() that avoids excessive IPIs. - Normalize the preemption/ipi setting code by introducing sched_shouldpreempt() so the logical is identical and not repeated between tdq_notify() and sched_setpreempt(). - In tdq_notify() don't set NEEDRESCHED as we may not actually own the thread lock this could have caused us to lose td_flags settings. - Garbage collect some tunables that are no longer relevant.
2008-03-10 01:32:01 +00:00
cpu = self;
- Make SCHED_STATS more generic by adding a wrapper to create the variables and sysctl nodes. - In reset walk the children of kern_sched_stats and reset the counters via the oid_arg1 pointer. This allows us to add arbitrary counters to the tree and still reset them properly. - Define a set of switch types to be passed with flags to mi_switch(). These types are named SWT_*. These types correspond to SCHED_STATS counters and are automatically handled in this way. - Make the new SWT_ types more specific than the older switch stats. There are now stats for idle switches, remote idle wakeups, remote preemption ithreads idling, etc. - Add switch statistics for ULE's pickcpu algorithm. These stats include how much migration there is, how often affinity was successful, how often threads were migrated to the local cpu on wakeup, etc. Sponsored by: Nokia
2008-04-17 04:20:10 +00:00
} else
SCHED_STAT_INC(pickcpu_lowest);
if (cpu != ts->ts_cpu)
SCHED_STAT_INC(pickcpu_migration);
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
return (cpu);
- Add static to local functions and data where it was missing. - Add an IPI based mechanism for migrating kses. This mechanism is broken down into several components. This is intended to reduce cache thrashing by eliminating most cases where one cpu touches another's run queues. - kseq_notify() appends a kse to a lockless singly linked list and conditionally sends an IPI to the target processor. Right now this is protected by sched_lock but at some point I'd like to get rid of the global lock. This is why I used something more complicated than a standard queue. - kseq_assign() processes our list of kses that have been assigned to us by other processors. This simply calls sched_add() for each item on the list after clearing the new KEF_ASSIGNED flag. This flag is used to indicate that we have been appeneded to the assigned queue but not added to the run queue yet. - In sched_add(), instead of adding a KSE to another processor's queue we use kse_notify() so that we don't touch their queue. Also in sched_add(), if KEF_ASSIGNED is already set return immediately. This can happen if a thread is removed and readded so that the priority is recorded properly. - In sched_rem() return immediately if KEF_ASSIGNED is set. All callers immediately readd simply to adjust priorites etc. - In sched_choose(), if we're running an IDLE task or the per cpu idle thread set our cpumask bit in 'kseq_idle' so that other processors may know that we are idle. Before this, make a single pass through the run queues of other processors so that we may find work more immediately if it is available. - In sched_runnable(), don't scan each processor's run queue, they will IPI us if they have work for us to do. - In sched_add(), if we're adding a thread that can be migrated and we have plenty of work to do, try to migrate the thread to an idle kseq. - Simplify the logic in sched_prio() and take the KEF_ASSIGNED flag into consideration. - No longer use kseq_choose() to steal threads, it can lose it's last argument. - Create a new function runq_steal() which operates like runq_choose() but skips threads based on some criteria. Currently it will not steal PRI_ITHD threads. In the future this will be used for CPU binding. - Create a kseq_steal() that checks each run queue with runq_steal(), use kseq_steal() in the places where we used kseq_choose() to steal with before.
2003-10-31 11:16:04 +00:00
}
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
#endif
- Make some context switches conditional on SCHED_STRICT_RESCHED. This may have some negative effect on interactivity but it yields great perf. gains. This also brings the conditions under which ULE context switches inline with SCHED_4BSD. - Define some new kseq_* functions for manipulating the run queue. - Add a new kseq member ksq_rslices and ksq_bload. rslices is the sum of the slices of runnable kses. This will be used for push load balance decisions. bload is the number of threads blocked waiting on IO.
2003-02-03 05:30:07 +00:00
- When stealing a kse in kseq_move() ignore the current kseq's min nice value. We want to steal any thread, even one that is not given a slice on its current queue.
2003-07-08 06:19:40 +00:00
/*
- Add static to local functions and data where it was missing. - Add an IPI based mechanism for migrating kses. This mechanism is broken down into several components. This is intended to reduce cache thrashing by eliminating most cases where one cpu touches another's run queues. - kseq_notify() appends a kse to a lockless singly linked list and conditionally sends an IPI to the target processor. Right now this is protected by sched_lock but at some point I'd like to get rid of the global lock. This is why I used something more complicated than a standard queue. - kseq_assign() processes our list of kses that have been assigned to us by other processors. This simply calls sched_add() for each item on the list after clearing the new KEF_ASSIGNED flag. This flag is used to indicate that we have been appeneded to the assigned queue but not added to the run queue yet. - In sched_add(), instead of adding a KSE to another processor's queue we use kse_notify() so that we don't touch their queue. Also in sched_add(), if KEF_ASSIGNED is already set return immediately. This can happen if a thread is removed and readded so that the priority is recorded properly. - In sched_rem() return immediately if KEF_ASSIGNED is set. All callers immediately readd simply to adjust priorites etc. - In sched_choose(), if we're running an IDLE task or the per cpu idle thread set our cpumask bit in 'kseq_idle' so that other processors may know that we are idle. Before this, make a single pass through the run queues of other processors so that we may find work more immediately if it is available. - In sched_runnable(), don't scan each processor's run queue, they will IPI us if they have work for us to do. - In sched_add(), if we're adding a thread that can be migrated and we have plenty of work to do, try to migrate the thread to an idle kseq. - Simplify the logic in sched_prio() and take the KEF_ASSIGNED flag into consideration. - No longer use kseq_choose() to steal threads, it can lose it's last argument. - Create a new function runq_steal() which operates like runq_choose() but skips threads based on some criteria. Currently it will not steal PRI_ITHD threads. In the future this will be used for CPU binding. - Create a kseq_steal() that checks each run queue with runq_steal(), use kseq_steal() in the places where we used kseq_choose() to steal with before.
2003-10-31 11:16:04 +00:00
* Pick the highest priority task we have and return it.
- When stealing a kse in kseq_move() ignore the current kseq's min nice value. We want to steal any thread, even one that is not given a slice on its current queue.
2003-07-08 06:19:40 +00:00
*/
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
static struct thread *
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
tdq_choose(struct tdq *tdq)
- Make some context switches conditional on SCHED_STRICT_RESCHED. This may have some negative effect on interactivity but it yields great perf. gains. This also brings the conditions under which ULE context switches inline with SCHED_4BSD. - Define some new kseq_* functions for manipulating the run queue. - Add a new kseq member ksq_rslices and ksq_bload. rslices is the sum of the slices of runnable kses. This will be used for push load balance decisions. bload is the number of threads blocked waiting on IO.
2003-02-03 05:30:07 +00:00
{
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
struct thread *td;
- Make some context switches conditional on SCHED_STRICT_RESCHED. This may have some negative effect on interactivity but it yields great perf. gains. This also brings the conditions under which ULE context switches inline with SCHED_4BSD. - Define some new kseq_* functions for manipulating the run queue. - Add a new kseq member ksq_rslices and ksq_bload. rslices is the sum of the slices of runnable kses. This will be used for push load balance decisions. bload is the number of threads blocked waiting on IO.
2003-02-03 05:30:07 +00:00
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
td = runq_choose(&tdq->tdq_realtime);
if (td != NULL)
return (td);
td = runq_choose_from(&tdq->tdq_timeshare, tdq->tdq_ridx);
if (td != NULL) {
Introduce two new helper macros to define the priority ranges used for interactive timeshare threads (PRI_*_INTERACTIVE) and non-interactive timeshare threads (PRI_*_BATCH) and use these instead of PRI_*_REALTIME and PRI_*_TIMESHARE. No functional change. Reviewed by: jeff
2011-01-13 14:22:27 +00:00
KASSERT(td->td_priority >= PRI_MIN_BATCH,
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
("tdq_choose: Invalid priority on timeshare queue %d",
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
td->td_priority));
return (td);
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
}
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
td = runq_choose(&tdq->tdq_idle);
if (td != NULL) {
KASSERT(td->td_priority >= PRI_MIN_IDLE,
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
("tdq_choose: Invalid priority on idle queue %d",
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
td->td_priority));
return (td);
- Make some context switches conditional on SCHED_STRICT_RESCHED. This may have some negative effect on interactivity but it yields great perf. gains. This also brings the conditions under which ULE context switches inline with SCHED_4BSD. - Define some new kseq_* functions for manipulating the run queue. - Add a new kseq member ksq_rslices and ksq_bload. rslices is the sum of the slices of runnable kses. This will be used for push load balance decisions. bload is the number of threads blocked waiting on IO.
2003-02-03 05:30:07 +00:00
}
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
return (NULL);
- Add in support for KSEs with 0 slice values on the run queue. If we try to select a KSE with a slice of 0 we will update its slice and insert it onto the next queue. - Pass the KSE instead of the ksegrp into sched_slice(). This more accurately reflects the behavior of the code. Slices are granted to kses. - Add a function kseq_nice_min() which finds the smallest nice value assigned to the kseg of any KSE on the queue. - Rewrite the logic in sched_slice(). Add a large comment describing the new slice selection scheme. To summarize, slices are assigned based on the nice value. Priorities are still calculated based on the nice and interactivity of a process. Slice sizes of 0 may be granted for KSEs whos nice is 20 or futher away from the lowest nice on the run queue. Other nice values are scaled across the range [min, min+20]. This fixes ULEs bad behavior with positively niced processes.
2003-04-02 06:46:43 +00:00
}
- Use ksq_load as the authoritive count of kses on the pair of kseqs for sched_runnable() et all. - Remove some dead code in sched_clock(). - Define two macros KSEQ_SELF() and KSEQ_CPU() for getting the kseq of the current cpu or some alternate cpu. - Start introducing kseq_() functions, such as kseq_choose() and kseq_setup().
2003-01-29 07:00:51 +00:00
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* Initialize a thread queue.
*/
- Use ksq_load as the authoritive count of kses on the pair of kseqs for sched_runnable() et all. - Remove some dead code in sched_clock(). - Define two macros KSEQ_SELF() and KSEQ_CPU() for getting the kseq of the current cpu or some alternate cpu. - Start introducing kseq_() functions, such as kseq_choose() and kseq_setup().
2003-01-29 07:00:51 +00:00
static void
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
tdq_setup(struct tdq *tdq)
- Use ksq_load as the authoritive count of kses on the pair of kseqs for sched_runnable() et all. - Remove some dead code in sched_clock(). - Define two macros KSEQ_SELF() and KSEQ_CPU() for getting the kseq of the current cpu or some alternate cpu. - Start introducing kseq_() functions, such as kseq_choose() and kseq_setup().
2003-01-29 07:00:51 +00:00
{
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
- Share scheduler locks between hyper-threaded cores to protect the tdq_group structure. Hyper-threaded cores won't really benefit from seperate locks anyway. - Seperate out the migration case from sched_switch to simplify the main switch code. We only migrate here if called via sched_bind(). - When preempted place the preempted thread back in the same queue at the head. - Improve the cpu group and topology infrastructure. Tested by: many on current@ Approved by: re
2007-08-03 23:38:46 +00:00
if (bootverbose)
printf("ULE: setup cpu %d\n", TDQ_ID(tdq));
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
runq_init(&tdq->tdq_realtime);
runq_init(&tdq->tdq_timeshare);
- Clean up a bit after the most recent KSE restructuring.
2006-12-29 10:37:07 +00:00
runq_init(&tdq->tdq_idle);
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
snprintf(tdq->tdq_name, sizeof(tdq->tdq_name),
"sched lock %d", (int)TDQ_ID(tdq));
mtx_init(&tdq->tdq_lock, tdq->tdq_name, "sched lock",
- Share scheduler locks between hyper-threaded cores to protect the tdq_group structure. Hyper-threaded cores won't really benefit from seperate locks anyway. - Seperate out the migration case from sched_switch to simplify the main switch code. We only migrate here if called via sched_bind(). - When preempted place the preempted thread back in the same queue at the head. - Improve the cpu group and topology infrastructure. Tested by: many on current@ Approved by: re
2007-08-03 23:38:46 +00:00
MTX_SPIN | MTX_RECURSE);
- Implement generic macros for producing KTR records that are compatible with src/tools/sched/schedgraph.py. This allows developers to quickly create a graphical view of ktr data for any resource in the system. - Add sched_tdname() and the pcpu field 'name' for quickly and uniformly identifying records associated with a thread or cpu. - Reimplement the KTR_SCHED traces using the new generic facility. Obtained from: attilio Discussed with: jhb Sponsored by: Nokia
2009-01-17 07:17:57 +00:00
#ifdef KTR
snprintf(tdq->tdq_loadname, sizeof(tdq->tdq_loadname),
"CPU %d load", (int)TDQ_ID(tdq));
#endif
- Share scheduler locks between hyper-threaded cores to protect the tdq_group structure. Hyper-threaded cores won't really benefit from seperate locks anyway. - Seperate out the migration case from sched_switch to simplify the main switch code. We only migrate here if called via sched_bind(). - When preempted place the preempted thread back in the same queue at the head. - Improve the cpu group and topology infrastructure. Tested by: many on current@ Approved by: re
2007-08-03 23:38:46 +00:00
}
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
#ifdef SMP
- Share scheduler locks between hyper-threaded cores to protect the tdq_group structure. Hyper-threaded cores won't really benefit from seperate locks anyway. - Seperate out the migration case from sched_switch to simplify the main switch code. We only migrate here if called via sched_bind(). - When preempted place the preempted thread back in the same queue at the head. - Improve the cpu group and topology infrastructure. Tested by: many on current@ Approved by: re
2007-08-03 23:38:46 +00:00
static void
sched_setup_smp(void)
{
struct tdq *tdq;
int i;
- Add a SYSCTL node for the ule scheduler. - Allow user adjustable min and max time slices (suggested by hiten). - Change the SLP_RUN_MAX to 100ms from 2 seconds so that we learn whether a process is interactive or not much more quickly. - Place a process on the current run queue if it is interactive or if it is running at an interrupt thread priority due to priority prop. - Use the 'current' timeshare queue for interrupt threads, realtime threads, and idle threads that are running at higher priority due to priority prop. This fixes problems where priorities would have been elevated but we would not check the timeshare run queue until other lower priority tasks were no longer runnable. - Keep an array of loads indexed by the priority class as well as a global load. - Keep an bucket of nice values with a count of the number of kses currently runnable with that nice value. - Keep track of the minimum nice value of any running thread. - Remove the unused short term sleep accounting. I was attempting to use this for load balancing but it didn't work out. - Define a kseq_print() for use with debugging. - Add KTR debugging at useful places so we can easily debug slice and priority assignment. - Decouple the runq assignment from the kseq assignment. kseq_add now keeps track of statistics. This is done so that the nice and load is still tracked for the currently running process. Previously if a niced process was added while a non nice process was running the niced process would still get a slice since it was not aware of the unnice process. - Make adjustments for the sched api changes.
2003-04-11 03:47:14 +00:00
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
cpu_top = smp_topo();
Update several places that iterate over CPUs to use CPU_FOREACH().
2010-06-11 18:46:34 +00:00
CPU_FOREACH(i) {
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
tdq = TDQ_CPU(i);
- Share scheduler locks between hyper-threaded cores to protect the tdq_group structure. Hyper-threaded cores won't really benefit from seperate locks anyway. - Seperate out the migration case from sched_switch to simplify the main switch code. We only migrate here if called via sched_bind(). - When preempted place the preempted thread back in the same queue at the head. - Improve the cpu group and topology infrastructure. Tested by: many on current@ Approved by: re
2007-08-03 23:38:46 +00:00
tdq_setup(tdq);
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
tdq->tdq_cg = smp_topo_find(cpu_top, i);
if (tdq->tdq_cg == NULL)
panic("Can't find cpu group for %d\n", i);
- Parse the cpu topology map in sched_setup(). - Associate logical CPUs on the same physical core with the same kseq. - Adjust code that assumed there would only be one running thread in any kseq. - Wrap the HTT code with a ULE_HTT_EXPERIMENTAL ifdef. This is a start towards HyperThreading support but it isn't quite there yet.
2003-07-04 19:59:00 +00:00
}
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
balance_tdq = TDQ_SELF();
sched_balance();
- Share scheduler locks between hyper-threaded cores to protect the tdq_group structure. Hyper-threaded cores won't really benefit from seperate locks anyway. - Seperate out the migration case from sched_switch to simplify the main switch code. We only migrate here if called via sched_bind(). - When preempted place the preempted thread back in the same queue at the head. - Improve the cpu group and topology infrastructure. Tested by: many on current@ Approved by: re
2007-08-03 23:38:46 +00:00
}
#endif
/*
* Setup the thread queues and initialize the topology based on MD
* information.
*/
static void
sched_setup(void *dummy)
{
struct tdq *tdq;
tdq = TDQ_SELF();
#ifdef SMP
- Remove the old smp cpu topology specification with a new, more flexible tree structure that encodes the level of cache sharing and other properties. - Provide several convenience functions for creating one and two level cpu trees as well as a default flat topology. The system now always has some topology. - On i386 and amd64 create a seperate level in the hierarchy for HTT and multi-core cpus. This will allow the scheduler to intelligently load balance non-uniform cores. Presently we don't detect what level of the cache hierarchy is shared at each level in the topology. - Add a mechanism for testing common topologies that have more information than the MD code is able to provide via the kern.smp.topology tunable. This should be considered a debugging tool only and not a stable api. Sponsored by: Nokia
2008-03-02 07:58:42 +00:00
sched_setup_smp();
- Parse the cpu topology map in sched_setup(). - Associate logical CPUs on the same physical core with the same kseq. - Adjust code that assumed there would only be one running thread in any kseq. - Wrap the HTT code with a ULE_HTT_EXPERIMENTAL ifdef. This is a start towards HyperThreading support but it isn't quite there yet.
2003-07-04 19:59:00 +00:00
#else
- Share scheduler locks between hyper-threaded cores to protect the tdq_group structure. Hyper-threaded cores won't really benefit from seperate locks anyway. - Seperate out the migration case from sched_switch to simplify the main switch code. We only migrate here if called via sched_bind(). - When preempted place the preempted thread back in the same queue at the head. - Improve the cpu group and topology infrastructure. Tested by: many on current@ Approved by: re
2007-08-03 23:38:46 +00:00
tdq_setup(tdq);
- Add a simple CPU load balancing algorithm. This works by executing once a second and equalizing the load between the two most imbalanced CPU. This is intended to clear up long term load imbalances that would not be handled by the 'pull' method in sched_choose(). - Pull out some bits of sched_choose() into a kseq_move() function that moves an arbitrary thread from one kseq to another.
2003-06-09 00:39:09 +00:00
#endif
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/* Add thread0's load since it's running. */
TDQ_LOCK(tdq);
- Share scheduler locks between hyper-threaded cores to protect the tdq_group structure. Hyper-threaded cores won't really benefit from seperate locks anyway. - Seperate out the migration case from sched_switch to simplify the main switch code. We only migrate here if called via sched_bind(). - When preempted place the preempted thread back in the same queue at the head. - Improve the cpu group and topology infrastructure. Tested by: many on current@ Approved by: re
2007-08-03 23:38:46 +00:00
thread0.td_lock = TDQ_LOCKPTR(TDQ_SELF());
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
tdq_load_add(tdq, &thread0);
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
tdq->tdq_lowpri = thread0.td_priority;
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
TDQ_UNLOCK(tdq);
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
}
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
Some minor tunings/cleanups inspired by bde@ after previous commits: - remove extra dynamic variable initializations; - restore (4BSD) and implement (ULE) hogticks variable setting; - make sched_rr_interval() more tolerant to options; - restore (4BSD) and implement (ULE) kern.sched.quantum sysctl, a more user-friendly wrapper for sched_slice; - tune some sysctl descriptions; - make some style fixes.
2012-08-10 19:02:49 +00:00
* This routine determines time constants after stathz and hz are setup.
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
*/
Fix a bug in slice calculation code, current code uses hz but sched_clock() is called by state clock. Submitted by: taku at tackymt dot homeip dot net
2005-12-19 08:26:09 +00:00
/* ARGSUSED */
static void
sched_initticks(void *dummy)
{
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
int incr;
Fix a bug in slice calculation code, current code uses hz but sched_clock() is called by state clock. Submitted by: taku at tackymt dot homeip dot net
2005-12-19 08:26:09 +00:00
realstathz = stathz ? stathz : hz;
- Change ULE to use dynamic slice sizes for the timeshare queue in order to further reduce latency for threads in this queue. This should help as threads transition from realtime to timeshare. The latency is bound to a max of sched_slice until we have more than sched_slice / 6 threads runnable. Then the min slice is allotted to all threads and latency becomes (nthreads - 1) * min_slice. Discussed with: mav
2012-11-08 01:46:47 +00:00
sched_slice = realstathz / SCHED_SLICE_DEFAULT_DIVISOR;
sched_slice_min = sched_slice / SCHED_SLICE_MIN_DIVISOR;
Some more minor tunings inspired by bde@.
2012-08-11 20:24:39 +00:00
hogticks = imax(1, (2 * hz * sched_slice + realstathz / 2) /
realstathz);
Fix a bug in slice calculation code, current code uses hz but sched_clock() is called by state clock. Submitted by: taku at tackymt dot homeip dot net
2005-12-19 08:26:09 +00:00
/*
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
* tickincr is shifted out by 10 to avoid rounding errors due to
- Only allow the tdq_idx to increase by one each tick rather than up to the most recently chosen index. This significantly improves nice behavior. This allows a lower priority thread to run some multiple of times before the higher priority thread makes it to the front of the queue. A nice +20 cpu hog now only gets ~5% of the cpu when running with a nice 0 cpu hog and about 1.5% with a nice -20 hog. A nice difference of 1 makes a 4% difference in cpu usage between two hogs. - Track a seperate insert and removal index. When the removal index is empty it is updated to point at the current insert index. - Don't remove and re-add a thread to the runq when it is being adjusted down in priority. - Pull some conditional code out of sched_tick(). It's looking a bit large now.
2007-01-04 12:16:19 +00:00
* hz not being evenly divisible by stathz on all platforms.
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
*/
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
incr = (hz << SCHED_TICK_SHIFT) / realstathz;
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
/*
* This does not work for values of stathz that are more than
* 1 << SCHED_TICK_SHIFT * hz. In practice this does not happen.
Fix a bug in slice calculation code, current code uses hz but sched_clock() is called by state clock. Submitted by: taku at tackymt dot homeip dot net
2005-12-19 08:26:09 +00:00
*/
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
if (incr == 0)
incr = 1;
tickincr = incr;
Major revamp of ULE's cpu load balancing: - Switch back to direct modification of remote CPU run queues. This added a lot of complexity with questionable gain. It's easy enough to reimplement if it's shown to help on huge machines. - Re-implement the old tdq_transfer() call as tdq_pickidle(). Change sched_add() so we have selectable cpu choosers and simplify the logic a bit here. - Implement tdq_pickpri() as the new default cpu chooser. This algorithm is similar to Solaris in that it tries to always run the threads with the best priorities. It is actually slightly more complex than solaris's algorithm because we also tend to favor the local cpu over other cpus which has a boost in latency but also potentially enables cache sharing between the waking thread and the woken thread. - Add a bunch of tunables that can be used to measure effects of different load balancing strategies. Most of these will go away once the algorithm is more definite. - Add a new mechanism to steal threads from busy cpus when we idle. This is enabled with kern.sched.steal_busy and kern.sched.busy_thresh. The threshold is the required length of a tdq's run queue before another cpu will be able to steal runnable threads. This prevents most queue imbalances that contribute the long latencies.
2007-01-19 21:56:08 +00:00
#ifdef SMP
- Move the rebalancer back into hardclock to prevent potential softclock starvation caused by unbalanced interrupt loads. - Change the rebalancer to work on stathz ticks but retain randomization. - Simplify locking in tdq_idled() to use the tdq_lock_pair() rather than complex sequences of locks to avoid deadlock. Reported by: kris Approved by: re
2007-10-02 00:36:06 +00:00
/*
* Set the default balance interval now that we know
* what realstathz is.
*/
balance_interval = realstathz;
Major revamp of ULE's cpu load balancing: - Switch back to direct modification of remote CPU run queues. This added a lot of complexity with questionable gain. It's easy enough to reimplement if it's shown to help on huge machines. - Re-implement the old tdq_transfer() call as tdq_pickidle(). Change sched_add() so we have selectable cpu choosers and simplify the logic a bit here. - Implement tdq_pickpri() as the new default cpu chooser. This algorithm is similar to Solaris in that it tries to always run the threads with the best priorities. It is actually slightly more complex than solaris's algorithm because we also tend to favor the local cpu over other cpus which has a boost in latency but also potentially enables cache sharing between the waking thread and the woken thread. - Add a bunch of tunables that can be used to measure effects of different load balancing strategies. Most of these will go away once the algorithm is more definite. - Add a new mechanism to steal threads from busy cpus when we idle. This is enabled with kern.sched.steal_busy and kern.sched.busy_thresh. The threshold is the required length of a tdq's run queue before another cpu will be able to steal runnable threads. This prevents most queue imbalances that contribute the long latencies.
2007-01-19 21:56:08 +00:00
affinity = SCHED_AFFINITY_DEFAULT;
#endif
Make kern.sched.idlespinthresh default value adaptive depending of HZ. Otherwise with HZ above 8000 CPU may never skip timer ticks on idle.
2012-03-09 19:09:08 +00:00
if (sched_idlespinthresh < 0)
Several optimizations to sched_idletd(): - Do not try to steal load from other CPUs if there was no contest switches on this CPU (i.e. it was idle all the time and woke up just for bus mastering or TLB shutdown). If current CPU was idle, then it is quite unlikely that some other CPU has load to steal. Under high I/O rate, when TLB shutdowns cause numerous CPU wakeups, on 24-CPU system load stealing code may consume up to 25% of all CPU time without giving any benefits. - Change code that implements spinning for load to restart spin in case of context switch. Previous code periodically called cpu_idle() even under high interrupt/context switch rate. - Rise spinning threshold to 10KHz, where it gives at least some effect that may worth consumed power. Reviewed by: jeff@
2012-11-10 07:02:57 +00:00
sched_idlespinthresh = 2 * max(10000, 6 * hz) / realstathz;
Fix a bug in slice calculation code, current code uses hz but sched_clock() is called by state clock. Submitted by: taku at tackymt dot homeip dot net
2005-12-19 08:26:09 +00:00
}
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* This is the core of the interactivity algorithm. Determines a score based
* on past behavior. It is the ratio of sleep time to run time scaled to
* a [0, 100] integer. This is the voluntary sleep time of a process, which
* differs from the cpu usage because it does not account for time spent
* waiting on a run-queue. Would be prettier if we had floating point.
Summary: Add the interactivity equations to the header comment for our interactivity calculation routine. Suggested by: rwatson
2015-08-26 16:36:41 +00:00
*
* When a thread's sleep time is greater than its run time the
* calculation is:
*
* scaling factor
* interactivity score = ---------------------
* sleep time / run time
*
*
* When a thread's run time is greater than its sleep time the
* calculation is:
*
* scaling factor
* interactivity score = --------------------- + scaling factor
* run time / sleep time
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
*/
static int
sched_interact_score(struct thread *td)
{
struct td_sched *ts;
int div;
Get rid of struct proc p_sched and struct thread td_sched pointers. p_sched is unused. The struct td_sched is always co-allocated with the struct thread, except for the thread0. Avoid useless indirection, instead calculate td_sched location using simple pointer arithmetic in td_get_sched(9). For thread0, which is statically allocated, create a structure to emulate layout of the dynamic allocation. Reviewed by: jhb (previous version) Sponsored by: The FreeBSD Foundation Differential revision: https://reviews.freebsd.org/D6711
2016-06-05 17:04:03 +00:00
ts = td_get_sched(td);
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* The score is only needed if this is likely to be an interactive
* task. Don't go through the expense of computing it if there's
* no chance.
*/
if (sched_interact <= SCHED_INTERACT_HALF &&
ts->ts_runtime >= ts->ts_slptime)
return (SCHED_INTERACT_HALF);
if (ts->ts_runtime > ts->ts_slptime) {
div = max(1, ts->ts_runtime / SCHED_INTERACT_HALF);
return (SCHED_INTERACT_HALF +
(SCHED_INTERACT_HALF - (ts->ts_slptime / div)));
}
if (ts->ts_slptime > ts->ts_runtime) {
div = max(1, ts->ts_slptime / SCHED_INTERACT_HALF);
return (ts->ts_runtime / div);
}
/* runtime == slptime */
if (ts->ts_runtime)
return (SCHED_INTERACT_HALF);
/*
* This can happen if slptime and runtime are 0.
*/
return (0);
}
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
/*
* Scale the scheduling priority according to the "interactivity" of this
* process.
*/
- Add a SYSCTL node for the ule scheduler. - Allow user adjustable min and max time slices (suggested by hiten). - Change the SLP_RUN_MAX to 100ms from 2 seconds so that we learn whether a process is interactive or not much more quickly. - Place a process on the current run queue if it is interactive or if it is running at an interrupt thread priority due to priority prop. - Use the 'current' timeshare queue for interrupt threads, realtime threads, and idle threads that are running at higher priority due to priority prop. This fixes problems where priorities would have been elevated but we would not check the timeshare run queue until other lower priority tasks were no longer runnable. - Keep an array of loads indexed by the priority class as well as a global load. - Keep an bucket of nice values with a count of the number of kses currently runnable with that nice value. - Keep track of the minimum nice value of any running thread. - Remove the unused short term sleep accounting. I was attempting to use this for load balancing but it didn't work out. - Define a kseq_print() for use with debugging. - Add KTR debugging at useful places so we can easily debug slice and priority assignment. - Decouple the runq assignment from the kseq assignment. kseq_add now keeps track of statistics. This is done so that the nice and load is still tracked for the currently running process. Previously if a niced process was added while a non nice process was running the niced process would still get a slice since it was not aware of the unnice process. - Make adjustments for the sched api changes.
2003-04-11 03:47:14 +00:00
static void
Make KSE a kernel option, turned on by default in all GENERIC kernel configs except sun4v (which doesn't process signals properly with KSE). Reviewed by: davidxu@
2006-10-26 21:42:22 +00:00
sched_priority(struct thread *td)
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
{
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
int score;
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
int pri;
Always use PRI_BASE() when checking the base type of a thread's priority class. MFC after: 2 weeks
2011-01-11 22:13:19 +00:00
if (PRI_BASE(td->td_pri_class) != PRI_TIMESHARE)
- Add a SYSCTL node for the ule scheduler. - Allow user adjustable min and max time slices (suggested by hiten). - Change the SLP_RUN_MAX to 100ms from 2 seconds so that we learn whether a process is interactive or not much more quickly. - Place a process on the current run queue if it is interactive or if it is running at an interrupt thread priority due to priority prop. - Use the 'current' timeshare queue for interrupt threads, realtime threads, and idle threads that are running at higher priority due to priority prop. This fixes problems where priorities would have been elevated but we would not check the timeshare run queue until other lower priority tasks were no longer runnable. - Keep an array of loads indexed by the priority class as well as a global load. - Keep an bucket of nice values with a count of the number of kses currently runnable with that nice value. - Keep track of the minimum nice value of any running thread. - Remove the unused short term sleep accounting. I was attempting to use this for load balancing but it didn't work out. - Define a kseq_print() for use with debugging. - Add KTR debugging at useful places so we can easily debug slice and priority assignment. - Decouple the runq assignment from the kseq assignment. kseq_add now keeps track of statistics. This is done so that the nice and load is still tracked for the currently running process. Previously if a niced process was added while a non nice process was running the niced process would still get a slice since it was not aware of the unnice process. - Make adjustments for the sched api changes.
2003-04-11 03:47:14 +00:00
return;
- Add in support for KSEs with 0 slice values on the run queue. If we try to select a KSE with a slice of 0 we will update its slice and insert it onto the next queue. - Pass the KSE instead of the ksegrp into sched_slice(). This more accurately reflects the behavior of the code. Slices are granted to kses. - Add a function kseq_nice_min() which finds the smallest nice value assigned to the kseg of any KSE on the queue. - Rewrite the logic in sched_slice(). Add a large comment describing the new slice selection scheme. To summarize, slices are assigned based on the nice value. Priorities are still calculated based on the nice and interactivity of a process. Slice sizes of 0 may be granted for KSEs whos nice is 20 or futher away from the lowest nice on the run queue. Other nice values are scaled across the range [min, min+20]. This fixes ULEs bad behavior with positively niced processes.
2003-04-02 06:46:43 +00:00
/*
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
* If the score is interactive we place the thread in the realtime
* queue with a priority that is less than kernel and interrupt
* priorities. These threads are not subject to nice restrictions.
- Add in support for KSEs with 0 slice values on the run queue. If we try to select a KSE with a slice of 0 we will update its slice and insert it onto the next queue. - Pass the KSE instead of the ksegrp into sched_slice(). This more accurately reflects the behavior of the code. Slices are granted to kses. - Add a function kseq_nice_min() which finds the smallest nice value assigned to the kseg of any KSE on the queue. - Rewrite the logic in sched_slice(). Add a large comment describing the new slice selection scheme. To summarize, slices are assigned based on the nice value. Priorities are still calculated based on the nice and interactivity of a process. Slice sizes of 0 may be granted for KSEs whos nice is 20 or futher away from the lowest nice on the run queue. Other nice values are scaled across the range [min, min+20]. This fixes ULEs bad behavior with positively niced processes.
2003-04-02 06:46:43 +00:00
*
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
* Scores greater than this are placed on the normal timeshare queue
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
* where the priority is partially decided by the most recent cpu
* utilization and the rest is decided by nice value.
- Improve grammar. s/it's/its/. - Improve load long-term load balancer by always IPIing exactly once. Previously the delay after rebalancing could cause problems with uneven workloads. - Allow nice to have a linear effect on the interactivity score. This allows negatively niced programs to stay interactive longer. It may be useful with very expensive Xorg servers under high loads. In general it should not be necessary to alter the nice level to improve interactive response. We may also want to consider never allowing positively niced processes to become interactive at all. - Initialize ccpu to 0 rather than 0.0. The decimal point was leftover from when the code was copied from 4bsd. ccpu is 0 in ULE because ULE only exports weighted cpu values. Reported by: Steve Kargl (Load balancing problem) Approved by: re
2007-09-22 02:20:14 +00:00
*
* The nice value of the process has a linear effect on the calculated
* score. Negative nice values make it easier for a thread to be
* considered interactive.
- Add in support for KSEs with 0 slice values on the run queue. If we try to select a KSE with a slice of 0 we will update its slice and insert it onto the next queue. - Pass the KSE instead of the ksegrp into sched_slice(). This more accurately reflects the behavior of the code. Slices are granted to kses. - Add a function kseq_nice_min() which finds the smallest nice value assigned to the kseg of any KSE on the queue. - Rewrite the logic in sched_slice(). Add a large comment describing the new slice selection scheme. To summarize, slices are assigned based on the nice value. Priorities are still calculated based on the nice and interactivity of a process. Slice sizes of 0 may be granted for KSEs whos nice is 20 or futher away from the lowest nice on the run queue. Other nice values are scaled across the range [min, min+20]. This fixes ULEs bad behavior with positively niced processes.
2003-04-02 06:46:43 +00:00
*/
Fix a sign bug in the handling of nice priorities when computing the interactive score for a thread. Submitted by: Taku YAMAMOTO taku of tackymt.homeip.net Reviewed by: jeff MFC after: 3 days
2009-10-15 11:41:12 +00:00
score = imax(0, sched_interact_score(td) + td->td_proc->p_nice);
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
if (score < sched_interact) {
Introduce two new helper macros to define the priority ranges used for interactive timeshare threads (PRI_*_INTERACTIVE) and non-interactive timeshare threads (PRI_*_BATCH) and use these instead of PRI_*_REALTIME and PRI_*_TIMESHARE. No functional change. Reviewed by: jeff
2011-01-13 14:22:27 +00:00
pri = PRI_MIN_INTERACT;
pri += ((PRI_MAX_INTERACT - PRI_MIN_INTERACT + 1) /
Fix two harmless off-by-one errors. Reviewed by: jeff MFC after: 2 weeks
2011-01-10 20:48:10 +00:00
sched_interact) * score;
Introduce two new helper macros to define the priority ranges used for interactive timeshare threads (PRI_*_INTERACTIVE) and non-interactive timeshare threads (PRI_*_BATCH) and use these instead of PRI_*_REALTIME and PRI_*_TIMESHARE. No functional change. Reviewed by: jeff
2011-01-13 14:22:27 +00:00
KASSERT(pri >= PRI_MIN_INTERACT && pri <= PRI_MAX_INTERACT,
- With a sleep time over 2097 seconds hzticks and slptime could end up negative. Use unsigned integers for sleep and run time so this doesn't disturb sched_interact_score(). This should fix the invalid interactive priority panics reported by several users.
2007-01-24 18:18:43 +00:00
("sched_priority: invalid interactive priority %d score %d",
pri, score));
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
} else {
pri = SCHED_PRI_MIN;
Get rid of struct proc p_sched and struct thread td_sched pointers. p_sched is unused. The struct td_sched is always co-allocated with the struct thread, except for the thread0. Avoid useless indirection, instead calculate td_sched location using simple pointer arithmetic in td_get_sched(9). For thread0, which is statically allocated, create a structure to emulate layout of the dynamic allocation. Reviewed by: jhb (previous version) Sponsored by: The FreeBSD Foundation Differential revision: https://reviews.freebsd.org/D6711
2016-06-05 17:04:03 +00:00
if (td_get_sched(td)->ts_ticks)
pri += min(SCHED_PRI_TICKS(td_get_sched(td)),
Fix an off-by-one error in r228960. The maximum priority delta provided by SCHED_PRI_TICKS should be SCHED_PRI_RANGE - 1 so that the resulting priority value (before nice adjustment) is between SCHED_PRI_MIN and SCHED_PRI_MAX, inclusive. Submitted by: kib Reported by: pho MFC after: 1 week
2013-12-03 14:50:12 +00:00
SCHED_PRI_RANGE - 1);
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
pri += SCHED_PRI_NICE(td->td_proc->p_nice);
Introduce two new helper macros to define the priority ranges used for interactive timeshare threads (PRI_*_INTERACTIVE) and non-interactive timeshare threads (PRI_*_BATCH) and use these instead of PRI_*_REALTIME and PRI_*_TIMESHARE. No functional change. Reviewed by: jeff
2011-01-13 14:22:27 +00:00
KASSERT(pri >= PRI_MIN_BATCH && pri <= PRI_MAX_BATCH,
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
("sched_priority: invalid priority %d: nice %d, "
"ticks %d ftick %d ltick %d tick pri %d",
Get rid of struct proc p_sched and struct thread td_sched pointers. p_sched is unused. The struct td_sched is always co-allocated with the struct thread, except for the thread0. Avoid useless indirection, instead calculate td_sched location using simple pointer arithmetic in td_get_sched(9). For thread0, which is statically allocated, create a structure to emulate layout of the dynamic allocation. Reviewed by: jhb (previous version) Sponsored by: The FreeBSD Foundation Differential revision: https://reviews.freebsd.org/D6711
2016-06-05 17:04:03 +00:00
pri, td->td_proc->p_nice, td_get_sched(td)->ts_ticks,
td_get_sched(td)->ts_ftick, td_get_sched(td)->ts_ltick,
SCHED_PRI_TICKS(td_get_sched(td))));
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
}
sched_user_prio(td, pri);
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
- Add in support for KSEs with 0 slice values on the run queue. If we try to select a KSE with a slice of 0 we will update its slice and insert it onto the next queue. - Pass the KSE instead of the ksegrp into sched_slice(). This more accurately reflects the behavior of the code. Slices are granted to kses. - Add a function kseq_nice_min() which finds the smallest nice value assigned to the kseg of any KSE on the queue. - Rewrite the logic in sched_slice(). Add a large comment describing the new slice selection scheme. To summarize, slices are assigned based on the nice value. Priorities are still calculated based on the nice and interactivity of a process. Slice sizes of 0 may be granted for KSEs whos nice is 20 or futher away from the lowest nice on the run queue. Other nice values are scaled across the range [min, min+20]. This fixes ULEs bad behavior with positively niced processes.
2003-04-02 06:46:43 +00:00
return;
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
}
- Change sched_interact_update() to only accept slp+runtime values between 0 and SCHED_SLP_RUN_MAX * 2. This allows us to simplify the algorithm quite a bit. Before, it dealt with arbitrary values which required us to do nasty integer division tricks that didn't quite work out correctly. - Chnage sched_wakeup() to detect conditions where the slp+runtime could exceed SCHED_SLP_RUN_MAX * 2. This can happen if we go to sleep for longer than 6 seconds. In this case, we'll just clear the runtime and set the sleep time to the max. - Define a new function, sched_interact_fork() which updates the slp+runtime of a newly forked thread. We want to limit the amount of history retained from the parent so that we learn the child's behavior quickly. We don't, however want to decay it to nothing. Previously, we would simply divide each parameter by 100 whenever we forked. After a few forks the values would reach 0 and tasks would not be considered interactive. - Add another KTR entry, cleanup some existing entries. - Remove a useless sched_interact_update() from sched_priority(). This is already done by the callers that require it.
2003-11-02 03:36:33 +00:00
/*
* This routine enforces a maximum limit on the amount of scheduling history
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
* kept. It is called after either the slptime or runtime is adjusted. This
* function is ugly due to integer math.
- Change sched_interact_update() to only accept slp+runtime values between 0 and SCHED_SLP_RUN_MAX * 2. This allows us to simplify the algorithm quite a bit. Before, it dealt with arbitrary values which required us to do nasty integer division tricks that didn't quite work out correctly. - Chnage sched_wakeup() to detect conditions where the slp+runtime could exceed SCHED_SLP_RUN_MAX * 2. This can happen if we go to sleep for longer than 6 seconds. In this case, we'll just clear the runtime and set the sleep time to the max. - Define a new function, sched_interact_fork() which updates the slp+runtime of a newly forked thread. We want to limit the amount of history retained from the parent so that we learn the child's behavior quickly. We don't, however want to decay it to nothing. Previously, we would simply divide each parameter by 100 whenever we forked. After a few forks the values would reach 0 and tasks would not be considered interactive. - Add another KTR entry, cleanup some existing entries. - Remove a useless sched_interact_update() from sched_priority(). This is already done by the callers that require it.
2003-11-02 03:36:33 +00:00
*/
- Add a new function "sched_interact_update()" that scales back the sleep and run time. - Scale the sleep and run time back via sched_interact_update() in more places. This is to keep the statistic more accurate. - Charge a parent one tick for forking a child. - Add only the run time and not the sleep time to the parents kg when a thread exits. This allows us to give a penalty for having an expensive thread exit but does not give a bonus for having an interactive thread exit. - Change the SLP_RUN_THROTTLE to limit us to 4/5th and not 1/2. - Change the SLP_RUN_MAX to two seconds. This keeps bursty interactive applications like mozilla and openoffice in the interactive range even through expensive tasks. - Recalculate the slice after every sleep. This ensures that once a task has been marked interactive it only has a slice of 1 at the risk of giving tasks that sleep for a very brief period a longer time slice.
2003-06-17 06:39:51 +00:00
static void
Make KSE a kernel option, turned on by default in all GENERIC kernel configs except sun4v (which doesn't process signals properly with KSE). Reviewed by: davidxu@
2006-10-26 21:42:22 +00:00
sched_interact_update(struct thread *td)
- Add a new function "sched_interact_update()" that scales back the sleep and run time. - Scale the sleep and run time back via sched_interact_update() in more places. This is to keep the statistic more accurate. - Charge a parent one tick for forking a child. - Add only the run time and not the sleep time to the parents kg when a thread exits. This allows us to give a penalty for having an expensive thread exit but does not give a bonus for having an interactive thread exit. - Change the SLP_RUN_THROTTLE to limit us to 4/5th and not 1/2. - Change the SLP_RUN_MAX to two seconds. This keeps bursty interactive applications like mozilla and openoffice in the interactive range even through expensive tasks. - Recalculate the slice after every sleep. This ensures that once a task has been marked interactive it only has a slice of 1 at the risk of giving tasks that sleep for a very brief period a longer time slice.
2003-06-17 06:39:51 +00:00
{
- Fix a comparison in sched_choose() that caused cpus to be constantly marked idle, thus breaking cpu load balancing. - Change sched_interact_update() to fix cases where the stored history has expanded significantly rather than handling them in the callers. This fixes a case where sched_priority() could compute a bad value. - Add a sysctl to disable the global load balancer for experimentation.
2007-01-05 23:45:38 +00:00
struct td_sched *ts;
- With a sleep time over 2097 seconds hzticks and slptime could end up negative. Use unsigned integers for sleep and run time so this doesn't disturb sched_interact_score(). This should fix the invalid interactive priority panics reported by several users.
2007-01-24 18:18:43 +00:00
u_int sum;
- Change sched_interact_update() to only accept slp+runtime values between 0 and SCHED_SLP_RUN_MAX * 2. This allows us to simplify the algorithm quite a bit. Before, it dealt with arbitrary values which required us to do nasty integer division tricks that didn't quite work out correctly. - Chnage sched_wakeup() to detect conditions where the slp+runtime could exceed SCHED_SLP_RUN_MAX * 2. This can happen if we go to sleep for longer than 6 seconds. In this case, we'll just clear the runtime and set the sleep time to the max. - Define a new function, sched_interact_fork() which updates the slp+runtime of a newly forked thread. We want to limit the amount of history retained from the parent so that we learn the child's behavior quickly. We don't, however want to decay it to nothing. Previously, we would simply divide each parameter by 100 whenever we forked. After a few forks the values would reach 0 and tasks would not be considered interactive. - Add another KTR entry, cleanup some existing entries. - Remove a useless sched_interact_update() from sched_priority(). This is already done by the callers that require it.
2003-11-02 03:36:33 +00:00
Get rid of struct proc p_sched and struct thread td_sched pointers. p_sched is unused. The struct td_sched is always co-allocated with the struct thread, except for the thread0. Avoid useless indirection, instead calculate td_sched location using simple pointer arithmetic in td_get_sched(9). For thread0, which is statically allocated, create a structure to emulate layout of the dynamic allocation. Reviewed by: jhb (previous version) Sponsored by: The FreeBSD Foundation Differential revision: https://reviews.freebsd.org/D6711
2016-06-05 17:04:03 +00:00
ts = td_get_sched(td);
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
sum = ts->ts_runtime + ts->ts_slptime;
- Change sched_interact_update() to only accept slp+runtime values between 0 and SCHED_SLP_RUN_MAX * 2. This allows us to simplify the algorithm quite a bit. Before, it dealt with arbitrary values which required us to do nasty integer division tricks that didn't quite work out correctly. - Chnage sched_wakeup() to detect conditions where the slp+runtime could exceed SCHED_SLP_RUN_MAX * 2. This can happen if we go to sleep for longer than 6 seconds. In this case, we'll just clear the runtime and set the sleep time to the max. - Define a new function, sched_interact_fork() which updates the slp+runtime of a newly forked thread. We want to limit the amount of history retained from the parent so that we learn the child's behavior quickly. We don't, however want to decay it to nothing. Previously, we would simply divide each parameter by 100 whenever we forked. After a few forks the values would reach 0 and tasks would not be considered interactive. - Add another KTR entry, cleanup some existing entries. - Remove a useless sched_interact_update() from sched_priority(). This is already done by the callers that require it.
2003-11-02 03:36:33 +00:00
if (sum < SCHED_SLP_RUN_MAX)
return;
- Fix a comparison in sched_choose() that caused cpus to be constantly marked idle, thus breaking cpu load balancing. - Change sched_interact_update() to fix cases where the stored history has expanded significantly rather than handling them in the callers. This fixes a case where sched_priority() could compute a bad value. - Add a sysctl to disable the global load balancer for experimentation.
2007-01-05 23:45:38 +00:00
/*
* This only happens from two places:
* 1) We have added an unusual amount of run time from fork_exit.
* 2) We have added an unusual amount of sleep time from sched_sleep().
*/
if (sum > SCHED_SLP_RUN_MAX * 2) {
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
if (ts->ts_runtime > ts->ts_slptime) {
ts->ts_runtime = SCHED_SLP_RUN_MAX;
ts->ts_slptime = 1;
- Fix a comparison in sched_choose() that caused cpus to be constantly marked idle, thus breaking cpu load balancing. - Change sched_interact_update() to fix cases where the stored history has expanded significantly rather than handling them in the callers. This fixes a case where sched_priority() could compute a bad value. - Add a sysctl to disable the global load balancer for experimentation.
2007-01-05 23:45:38 +00:00
} else {
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
ts->ts_slptime = SCHED_SLP_RUN_MAX;
ts->ts_runtime = 1;
- Fix a comparison in sched_choose() that caused cpus to be constantly marked idle, thus breaking cpu load balancing. - Change sched_interact_update() to fix cases where the stored history has expanded significantly rather than handling them in the callers. This fixes a case where sched_priority() could compute a bad value. - Add a sysctl to disable the global load balancer for experimentation.
2007-01-05 23:45:38 +00:00
}
return;
}
- Change sched_interact_update() to only accept slp+runtime values between 0 and SCHED_SLP_RUN_MAX * 2. This allows us to simplify the algorithm quite a bit. Before, it dealt with arbitrary values which required us to do nasty integer division tricks that didn't quite work out correctly. - Chnage sched_wakeup() to detect conditions where the slp+runtime could exceed SCHED_SLP_RUN_MAX * 2. This can happen if we go to sleep for longer than 6 seconds. In this case, we'll just clear the runtime and set the sleep time to the max. - Define a new function, sched_interact_fork() which updates the slp+runtime of a newly forked thread. We want to limit the amount of history retained from the parent so that we learn the child's behavior quickly. We don't, however want to decay it to nothing. Previously, we would simply divide each parameter by 100 whenever we forked. After a few forks the values would reach 0 and tasks would not be considered interactive. - Add another KTR entry, cleanup some existing entries. - Remove a useless sched_interact_update() from sched_priority(). This is already done by the callers that require it.
2003-11-02 03:36:33 +00:00
/*
* If we have exceeded by more than 1/5th then the algorithm below
* will not bring us back into range. Dividing by two here forces
- Use a new flag, KEF_XFERABLE, to record with certainty that this kse had contributed to the transferable load count. This prevents any potential problems with sched_pin() being used around calls to setrunqueue(). - Change the sched_add() load balancing algorithm to try to migrate on wakeup. This attempts to place threads that communicate with each other on the same CPU. - Don't clear the idle counts in kseq_transfer(), let the cpus do that when they call sched_add() from kseq_assign(). - Correct a few out of date comments. - Make sure the ke_cpu field is correct when we preempt. - Call kseq_assign() from sched_clock() to catch any assignments that were done without IPI. Presently all assignments are done with an IPI, but I'm trying a patch that limits that. - Don't migrate a thread if it is still runnable in sched_add(). Previously, this could only happen for KSE threads, but due to changes to sched_switch() all threads went through this path. - Remove some code that was added with preemption but is not necessary.
2004-08-10 07:52:21 +00:00
* us into the range of [4/5 * SCHED_INTERACT_MAX, SCHED_INTERACT_MAX]
- Change sched_interact_update() to only accept slp+runtime values between 0 and SCHED_SLP_RUN_MAX * 2. This allows us to simplify the algorithm quite a bit. Before, it dealt with arbitrary values which required us to do nasty integer division tricks that didn't quite work out correctly. - Chnage sched_wakeup() to detect conditions where the slp+runtime could exceed SCHED_SLP_RUN_MAX * 2. This can happen if we go to sleep for longer than 6 seconds. In this case, we'll just clear the runtime and set the sleep time to the max. - Define a new function, sched_interact_fork() which updates the slp+runtime of a newly forked thread. We want to limit the amount of history retained from the parent so that we learn the child's behavior quickly. We don't, however want to decay it to nothing. Previously, we would simply divide each parameter by 100 whenever we forked. After a few forks the values would reach 0 and tasks would not be considered interactive. - Add another KTR entry, cleanup some existing entries. - Remove a useless sched_interact_update() from sched_priority(). This is already done by the callers that require it.
2003-11-02 03:36:33 +00:00
*/
- Use the proper constant in sched_interact_update(). Previously, SCHED_INTERACT_MAX was used where SCHED_SLP_RUN_MAX was needed. This was causing the interactivity scaler to lose history at a more dramatic rate than intended.
2004-04-04 19:12:56 +00:00
if (sum > (SCHED_SLP_RUN_MAX / 5) * 6) {
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
ts->ts_runtime /= 2;
ts->ts_slptime /= 2;
- Change sched_interact_update() to only accept slp+runtime values between 0 and SCHED_SLP_RUN_MAX * 2. This allows us to simplify the algorithm quite a bit. Before, it dealt with arbitrary values which required us to do nasty integer division tricks that didn't quite work out correctly. - Chnage sched_wakeup() to detect conditions where the slp+runtime could exceed SCHED_SLP_RUN_MAX * 2. This can happen if we go to sleep for longer than 6 seconds. In this case, we'll just clear the runtime and set the sleep time to the max. - Define a new function, sched_interact_fork() which updates the slp+runtime of a newly forked thread. We want to limit the amount of history retained from the parent so that we learn the child's behavior quickly. We don't, however want to decay it to nothing. Previously, we would simply divide each parameter by 100 whenever we forked. After a few forks the values would reach 0 and tasks would not be considered interactive. - Add another KTR entry, cleanup some existing entries. - Remove a useless sched_interact_update() from sched_priority(). This is already done by the callers that require it.
2003-11-02 03:36:33 +00:00
return;
}
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
ts->ts_runtime = (ts->ts_runtime / 5) * 4;
ts->ts_slptime = (ts->ts_slptime / 5) * 4;
- Change sched_interact_update() to only accept slp+runtime values between 0 and SCHED_SLP_RUN_MAX * 2. This allows us to simplify the algorithm quite a bit. Before, it dealt with arbitrary values which required us to do nasty integer division tricks that didn't quite work out correctly. - Chnage sched_wakeup() to detect conditions where the slp+runtime could exceed SCHED_SLP_RUN_MAX * 2. This can happen if we go to sleep for longer than 6 seconds. In this case, we'll just clear the runtime and set the sleep time to the max. - Define a new function, sched_interact_fork() which updates the slp+runtime of a newly forked thread. We want to limit the amount of history retained from the parent so that we learn the child's behavior quickly. We don't, however want to decay it to nothing. Previously, we would simply divide each parameter by 100 whenever we forked. After a few forks the values would reach 0 and tasks would not be considered interactive. - Add another KTR entry, cleanup some existing entries. - Remove a useless sched_interact_update() from sched_priority(). This is already done by the callers that require it.
2003-11-02 03:36:33 +00:00
}
- Use a better algorithm in sched_pctcpu_update() Contributed by: Thomaswuerfl@gmx.de - In sched_prio(), adjust the run queue for threads which may need to move to the current queue due to priority propagation . - In sched_switch(), fix style bug introduced when the KSE support went in. Columns are 80 chars wide, not 90. - In sched_switch(), Fix the comparison in the idle case and explicitly re-initialize the runq in the not propagated case. - Remove dead code in sched_clock(). - In sched_clock(), If we're an IDLE class td set NEEDRESCHED so that threads that have become runnable will get a chance to. - In sched_runnable(), if we're not the IDLETD, we should not consider curthread when examining the load. This mimics the 4BSD behavior of returning 0 when the only runnable thread is running. - In sched_userret(), remove the code for setting NEEDRESCHED entirely. This is not necessary and is not implemented in 4BSD. - Use the correct comparison in sched_add() when checking to see if an idle prio task has had it's priority temporarily elevated.
2003-10-27 06:47:05 +00:00
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* Scale back the interactivity history when a child thread is created. The
* history is inherited from the parent but the thread may behave totally
* differently. For example, a shell spawning a compiler process. We want
* to learn that the compiler is behaving badly very quickly.
*/
- Change sched_interact_update() to only accept slp+runtime values between 0 and SCHED_SLP_RUN_MAX * 2. This allows us to simplify the algorithm quite a bit. Before, it dealt with arbitrary values which required us to do nasty integer division tricks that didn't quite work out correctly. - Chnage sched_wakeup() to detect conditions where the slp+runtime could exceed SCHED_SLP_RUN_MAX * 2. This can happen if we go to sleep for longer than 6 seconds. In this case, we'll just clear the runtime and set the sleep time to the max. - Define a new function, sched_interact_fork() which updates the slp+runtime of a newly forked thread. We want to limit the amount of history retained from the parent so that we learn the child's behavior quickly. We don't, however want to decay it to nothing. Previously, we would simply divide each parameter by 100 whenever we forked. After a few forks the values would reach 0 and tasks would not be considered interactive. - Add another KTR entry, cleanup some existing entries. - Remove a useless sched_interact_update() from sched_priority(). This is already done by the callers that require it.
2003-11-02 03:36:33 +00:00
static void
Make KSE a kernel option, turned on by default in all GENERIC kernel configs except sun4v (which doesn't process signals properly with KSE). Reviewed by: davidxu@
2006-10-26 21:42:22 +00:00
sched_interact_fork(struct thread *td)
- Change sched_interact_update() to only accept slp+runtime values between 0 and SCHED_SLP_RUN_MAX * 2. This allows us to simplify the algorithm quite a bit. Before, it dealt with arbitrary values which required us to do nasty integer division tricks that didn't quite work out correctly. - Chnage sched_wakeup() to detect conditions where the slp+runtime could exceed SCHED_SLP_RUN_MAX * 2. This can happen if we go to sleep for longer than 6 seconds. In this case, we'll just clear the runtime and set the sleep time to the max. - Define a new function, sched_interact_fork() which updates the slp+runtime of a newly forked thread. We want to limit the amount of history retained from the parent so that we learn the child's behavior quickly. We don't, however want to decay it to nothing. Previously, we would simply divide each parameter by 100 whenever we forked. After a few forks the values would reach 0 and tasks would not be considered interactive. - Add another KTR entry, cleanup some existing entries. - Remove a useless sched_interact_update() from sched_priority(). This is already done by the callers that require it.
2003-11-02 03:36:33 +00:00
{
Get rid of struct proc p_sched and struct thread td_sched pointers. p_sched is unused. The struct td_sched is always co-allocated with the struct thread, except for the thread0. Avoid useless indirection, instead calculate td_sched location using simple pointer arithmetic in td_get_sched(9). For thread0, which is statically allocated, create a structure to emulate layout of the dynamic allocation. Reviewed by: jhb (previous version) Sponsored by: The FreeBSD Foundation Differential revision: https://reviews.freebsd.org/D6711
2016-06-05 17:04:03 +00:00
struct td_sched *ts;
- Change sched_interact_update() to only accept slp+runtime values between 0 and SCHED_SLP_RUN_MAX * 2. This allows us to simplify the algorithm quite a bit. Before, it dealt with arbitrary values which required us to do nasty integer division tricks that didn't quite work out correctly. - Chnage sched_wakeup() to detect conditions where the slp+runtime could exceed SCHED_SLP_RUN_MAX * 2. This can happen if we go to sleep for longer than 6 seconds. In this case, we'll just clear the runtime and set the sleep time to the max. - Define a new function, sched_interact_fork() which updates the slp+runtime of a newly forked thread. We want to limit the amount of history retained from the parent so that we learn the child's behavior quickly. We don't, however want to decay it to nothing. Previously, we would simply divide each parameter by 100 whenever we forked. After a few forks the values would reach 0 and tasks would not be considered interactive. - Add another KTR entry, cleanup some existing entries. - Remove a useless sched_interact_update() from sched_priority(). This is already done by the callers that require it.
2003-11-02 03:36:33 +00:00
int ratio;
int sum;
Get rid of struct proc p_sched and struct thread td_sched pointers. p_sched is unused. The struct td_sched is always co-allocated with the struct thread, except for the thread0. Avoid useless indirection, instead calculate td_sched location using simple pointer arithmetic in td_get_sched(9). For thread0, which is statically allocated, create a structure to emulate layout of the dynamic allocation. Reviewed by: jhb (previous version) Sponsored by: The FreeBSD Foundation Differential revision: https://reviews.freebsd.org/D6711
2016-06-05 17:04:03 +00:00
ts = td_get_sched(td);
sum = ts->ts_runtime + ts->ts_slptime;
- Change sched_interact_update() to only accept slp+runtime values between 0 and SCHED_SLP_RUN_MAX * 2. This allows us to simplify the algorithm quite a bit. Before, it dealt with arbitrary values which required us to do nasty integer division tricks that didn't quite work out correctly. - Chnage sched_wakeup() to detect conditions where the slp+runtime could exceed SCHED_SLP_RUN_MAX * 2. This can happen if we go to sleep for longer than 6 seconds. In this case, we'll just clear the runtime and set the sleep time to the max. - Define a new function, sched_interact_fork() which updates the slp+runtime of a newly forked thread. We want to limit the amount of history retained from the parent so that we learn the child's behavior quickly. We don't, however want to decay it to nothing. Previously, we would simply divide each parameter by 100 whenever we forked. After a few forks the values would reach 0 and tasks would not be considered interactive. - Add another KTR entry, cleanup some existing entries. - Remove a useless sched_interact_update() from sched_priority(). This is already done by the callers that require it.
2003-11-02 03:36:33 +00:00
if (sum > SCHED_SLP_RUN_FORK) {
ratio = sum / SCHED_SLP_RUN_FORK;
Get rid of struct proc p_sched and struct thread td_sched pointers. p_sched is unused. The struct td_sched is always co-allocated with the struct thread, except for the thread0. Avoid useless indirection, instead calculate td_sched location using simple pointer arithmetic in td_get_sched(9). For thread0, which is statically allocated, create a structure to emulate layout of the dynamic allocation. Reviewed by: jhb (previous version) Sponsored by: The FreeBSD Foundation Differential revision: https://reviews.freebsd.org/D6711
2016-06-05 17:04:03 +00:00
ts->ts_runtime /= ratio;
ts->ts_slptime /= ratio;
- Add a new function "sched_interact_update()" that scales back the sleep and run time. - Scale the sleep and run time back via sched_interact_update() in more places. This is to keep the statistic more accurate. - Charge a parent one tick for forking a child. - Add only the run time and not the sleep time to the parents kg when a thread exits. This allows us to give a penalty for having an expensive thread exit but does not give a bonus for having an interactive thread exit. - Change the SLP_RUN_THROTTLE to limit us to 4/5th and not 1/2. - Change the SLP_RUN_MAX to two seconds. This keeps bursty interactive applications like mozilla and openoffice in the interactive range even through expensive tasks. - Recalculate the slice after every sleep. This ensures that once a task has been marked interactive it only has a slice of 1 at the risk of giving tasks that sleep for a very brief period a longer time slice.
2003-06-17 06:39:51 +00:00
}
}
Refactor a bunch of scheduler code to give basically the same behaviour but with slightly cleaned up interfaces. The KSE structure has become the same as the "per thread scheduler private data" structure. In order to not make the diffs too great one is #defined as the other at this time. The KSE (or td_sched) structure is now allocated per thread and has no allocation code of its own. Concurrency for a KSEGRP is now kept track of via a simple pair of counters rather than using KSE structures as tokens. Since the KSE structure is different in each scheduler, kern_switch.c is now included at the end of each scheduler. Nothing outside the scheduler knows the contents of the KSE (aka td_sched) structure. The fields in the ksegrp structure that are to do with the scheduler's queueing mechanisms are now moved to the kg_sched structure. (per ksegrp scheduler private data structure). In other words how the scheduler queues and keeps track of threads is no-one's business except the scheduler's. This should allow people to write experimental schedulers with completely different internal structuring. A scheduler call sched_set_concurrency(kg, N) has been added that notifies teh scheduler that no more than N threads from that ksegrp should be allowed to be on concurrently scheduled. This is also used to enforce 'fainess' at this time so that a ksegrp with 10000 threads can not swamp a the run queue and force out a process with 1 thread, since the current code will not set the concurrency above NCPU, and both schedulers will not allow more than that many onto the system run queue at a time. Each scheduler should eventualy develop their own methods to do this now that they are effectively separated. Rejig libthr's kernel interface to follow the same code paths as linkse for scope system threads. This has slightly hurt libthr's performance but I will work to recover as much of it as I can. Thread exit code has been cleaned up greatly. exit and exec code now transitions a process back to 'standard non-threaded mode' before taking the next step. Reviewed by: scottl, peter MFC after: 1 week
2004-09-05 02:09:54 +00:00
/*
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
* Called from proc0_init() to setup the scheduler fields.
Refactor a bunch of scheduler code to give basically the same behaviour but with slightly cleaned up interfaces. The KSE structure has become the same as the "per thread scheduler private data" structure. In order to not make the diffs too great one is #defined as the other at this time. The KSE (or td_sched) structure is now allocated per thread and has no allocation code of its own. Concurrency for a KSEGRP is now kept track of via a simple pair of counters rather than using KSE structures as tokens. Since the KSE structure is different in each scheduler, kern_switch.c is now included at the end of each scheduler. Nothing outside the scheduler knows the contents of the KSE (aka td_sched) structure. The fields in the ksegrp structure that are to do with the scheduler's queueing mechanisms are now moved to the kg_sched structure. (per ksegrp scheduler private data structure). In other words how the scheduler queues and keeps track of threads is no-one's business except the scheduler's. This should allow people to write experimental schedulers with completely different internal structuring. A scheduler call sched_set_concurrency(kg, N) has been added that notifies teh scheduler that no more than N threads from that ksegrp should be allowed to be on concurrently scheduled. This is also used to enforce 'fainess' at this time so that a ksegrp with 10000 threads can not swamp a the run queue and force out a process with 1 thread, since the current code will not set the concurrency above NCPU, and both schedulers will not allow more than that many onto the system run queue at a time. Each scheduler should eventualy develop their own methods to do this now that they are effectively separated. Rejig libthr's kernel interface to follow the same code paths as linkse for scope system threads. This has slightly hurt libthr's performance but I will work to recover as much of it as I can. Thread exit code has been cleaned up greatly. exit and exec code now transitions a process back to 'standard non-threaded mode' before taking the next step. Reviewed by: scottl, peter MFC after: 1 week
2004-09-05 02:09:54 +00:00
*/
void
schedinit(void)
{
Get rid of struct proc p_sched and struct thread td_sched pointers. p_sched is unused. The struct td_sched is always co-allocated with the struct thread, except for the thread0. Avoid useless indirection, instead calculate td_sched location using simple pointer arithmetic in td_get_sched(9). For thread0, which is statically allocated, create a structure to emulate layout of the dynamic allocation. Reviewed by: jhb (previous version) Sponsored by: The FreeBSD Foundation Differential revision: https://reviews.freebsd.org/D6711
2016-06-05 17:04:03 +00:00
struct td_sched *ts0;
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
Refactor a bunch of scheduler code to give basically the same behaviour but with slightly cleaned up interfaces. The KSE structure has become the same as the "per thread scheduler private data" structure. In order to not make the diffs too great one is #defined as the other at this time. The KSE (or td_sched) structure is now allocated per thread and has no allocation code of its own. Concurrency for a KSEGRP is now kept track of via a simple pair of counters rather than using KSE structures as tokens. Since the KSE structure is different in each scheduler, kern_switch.c is now included at the end of each scheduler. Nothing outside the scheduler knows the contents of the KSE (aka td_sched) structure. The fields in the ksegrp structure that are to do with the scheduler's queueing mechanisms are now moved to the kg_sched structure. (per ksegrp scheduler private data structure). In other words how the scheduler queues and keeps track of threads is no-one's business except the scheduler's. This should allow people to write experimental schedulers with completely different internal structuring. A scheduler call sched_set_concurrency(kg, N) has been added that notifies teh scheduler that no more than N threads from that ksegrp should be allowed to be on concurrently scheduled. This is also used to enforce 'fainess' at this time so that a ksegrp with 10000 threads can not swamp a the run queue and force out a process with 1 thread, since the current code will not set the concurrency above NCPU, and both schedulers will not allow more than that many onto the system run queue at a time. Each scheduler should eventualy develop their own methods to do this now that they are effectively separated. Rejig libthr's kernel interface to follow the same code paths as linkse for scope system threads. This has slightly hurt libthr's performance but I will work to recover as much of it as I can. Thread exit code has been cleaned up greatly. exit and exec code now transitions a process back to 'standard non-threaded mode' before taking the next step. Reviewed by: scottl, peter MFC after: 1 week
2004-09-05 02:09:54 +00:00
/*
Get rid of struct proc p_sched and struct thread td_sched pointers. p_sched is unused. The struct td_sched is always co-allocated with the struct thread, except for the thread0. Avoid useless indirection, instead calculate td_sched location using simple pointer arithmetic in td_get_sched(9). For thread0, which is statically allocated, create a structure to emulate layout of the dynamic allocation. Reviewed by: jhb (previous version) Sponsored by: The FreeBSD Foundation Differential revision: https://reviews.freebsd.org/D6711
2016-06-05 17:04:03 +00:00
* Set up the scheduler specific parts of thread0.
Refactor a bunch of scheduler code to give basically the same behaviour but with slightly cleaned up interfaces. The KSE structure has become the same as the "per thread scheduler private data" structure. In order to not make the diffs too great one is #defined as the other at this time. The KSE (or td_sched) structure is now allocated per thread and has no allocation code of its own. Concurrency for a KSEGRP is now kept track of via a simple pair of counters rather than using KSE structures as tokens. Since the KSE structure is different in each scheduler, kern_switch.c is now included at the end of each scheduler. Nothing outside the scheduler knows the contents of the KSE (aka td_sched) structure. The fields in the ksegrp structure that are to do with the scheduler's queueing mechanisms are now moved to the kg_sched structure. (per ksegrp scheduler private data structure). In other words how the scheduler queues and keeps track of threads is no-one's business except the scheduler's. This should allow people to write experimental schedulers with completely different internal structuring. A scheduler call sched_set_concurrency(kg, N) has been added that notifies teh scheduler that no more than N threads from that ksegrp should be allowed to be on concurrently scheduled. This is also used to enforce 'fainess' at this time so that a ksegrp with 10000 threads can not swamp a the run queue and force out a process with 1 thread, since the current code will not set the concurrency above NCPU, and both schedulers will not allow more than that many onto the system run queue at a time. Each scheduler should eventualy develop their own methods to do this now that they are effectively separated. Rejig libthr's kernel interface to follow the same code paths as linkse for scope system threads. This has slightly hurt libthr's performance but I will work to recover as much of it as I can. Thread exit code has been cleaned up greatly. exit and exec code now transitions a process back to 'standard non-threaded mode' before taking the next step. Reviewed by: scottl, peter MFC after: 1 week
2004-09-05 02:09:54 +00:00
*/
Get rid of struct proc p_sched and struct thread td_sched pointers. p_sched is unused. The struct td_sched is always co-allocated with the struct thread, except for the thread0. Avoid useless indirection, instead calculate td_sched location using simple pointer arithmetic in td_get_sched(9). For thread0, which is statically allocated, create a structure to emulate layout of the dynamic allocation. Reviewed by: jhb (previous version) Sponsored by: The FreeBSD Foundation Differential revision: https://reviews.freebsd.org/D6711
2016-06-05 17:04:03 +00:00
ts0 = td_get_sched(&thread0);
ts0->ts_ltick = ticks;
ts0->ts_ftick = ticks;
ts0->ts_slice = 0;
The sched_add() function is not only used when the thread is initially started, but also by the turnstiles to mark a thread as runnable for all locks, for instance sleepqueues do: setrunnable()->sched_wakeup()->sched_add() In r326218 code was added to allow booting from non-zero CPU numbers by setting the ts_cpu field inside the ULE scheduler's sched_add() function. This had an undesired side-effect that prior sched_pin() and sched_bind() calls got disregarded. This patch fixes the initialization of the ts_cpu field for the ULE scheduler to only happen once when the initial thread is constructed during system init. Forking will then later on ensure that a valid ts_cpu value gets copied to all children. Reviewed by: jhb, kib Discussed with: nwhitehorn MFC after: 1 month Differential revision: https://reviews.freebsd.org/D13298 Sponsored by: Mellanox Technologies
2017-11-29 23:28:40 +00:00
ts0->ts_cpu = curcpu; /* set valid CPU number */
Refactor a bunch of scheduler code to give basically the same behaviour but with slightly cleaned up interfaces. The KSE structure has become the same as the "per thread scheduler private data" structure. In order to not make the diffs too great one is #defined as the other at this time. The KSE (or td_sched) structure is now allocated per thread and has no allocation code of its own. Concurrency for a KSEGRP is now kept track of via a simple pair of counters rather than using KSE structures as tokens. Since the KSE structure is different in each scheduler, kern_switch.c is now included at the end of each scheduler. Nothing outside the scheduler knows the contents of the KSE (aka td_sched) structure. The fields in the ksegrp structure that are to do with the scheduler's queueing mechanisms are now moved to the kg_sched structure. (per ksegrp scheduler private data structure). In other words how the scheduler queues and keeps track of threads is no-one's business except the scheduler's. This should allow people to write experimental schedulers with completely different internal structuring. A scheduler call sched_set_concurrency(kg, N) has been added that notifies teh scheduler that no more than N threads from that ksegrp should be allowed to be on concurrently scheduled. This is also used to enforce 'fainess' at this time so that a ksegrp with 10000 threads can not swamp a the run queue and force out a process with 1 thread, since the current code will not set the concurrency above NCPU, and both schedulers will not allow more than that many onto the system run queue at a time. Each scheduler should eventualy develop their own methods to do this now that they are effectively separated. Rejig libthr's kernel interface to follow the same code paths as linkse for scope system threads. This has slightly hurt libthr's performance but I will work to recover as much of it as I can. Thread exit code has been cleaned up greatly. exit and exec code now transitions a process back to 'standard non-threaded mode' before taking the next step. Reviewed by: scottl, peter MFC after: 1 week
2004-09-05 02:09:54 +00:00
}
- Add a SYSCTL node for the ule scheduler. - Allow user adjustable min and max time slices (suggested by hiten). - Change the SLP_RUN_MAX to 100ms from 2 seconds so that we learn whether a process is interactive or not much more quickly. - Place a process on the current run queue if it is interactive or if it is running at an interrupt thread priority due to priority prop. - Use the 'current' timeshare queue for interrupt threads, realtime threads, and idle threads that are running at higher priority due to priority prop. This fixes problems where priorities would have been elevated but we would not check the timeshare run queue until other lower priority tasks were no longer runnable. - Keep an array of loads indexed by the priority class as well as a global load. - Keep an bucket of nice values with a count of the number of kses currently runnable with that nice value. - Keep track of the minimum nice value of any running thread. - Remove the unused short term sleep accounting. I was attempting to use this for load balancing but it didn't work out. - Define a kseq_print() for use with debugging. - Add KTR debugging at useful places so we can easily debug slice and priority assignment. - Decouple the runq assignment from the kseq assignment. kseq_add now keeps track of statistics. This is done so that the nice and load is still tracked for the currently running process. Previously if a niced process was added while a non nice process was running the niced process would still get a slice since it was not aware of the unnice process. - Make adjustments for the sched api changes.
2003-04-11 03:47:14 +00:00
/*
* This is only somewhat accurate since given many processes of the same
* priority they will switch when their slices run out, which will be
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
* at most sched_slice stathz ticks.
- Add a SYSCTL node for the ule scheduler. - Allow user adjustable min and max time slices (suggested by hiten). - Change the SLP_RUN_MAX to 100ms from 2 seconds so that we learn whether a process is interactive or not much more quickly. - Place a process on the current run queue if it is interactive or if it is running at an interrupt thread priority due to priority prop. - Use the 'current' timeshare queue for interrupt threads, realtime threads, and idle threads that are running at higher priority due to priority prop. This fixes problems where priorities would have been elevated but we would not check the timeshare run queue until other lower priority tasks were no longer runnable. - Keep an array of loads indexed by the priority class as well as a global load. - Keep an bucket of nice values with a count of the number of kses currently runnable with that nice value. - Keep track of the minimum nice value of any running thread. - Remove the unused short term sleep accounting. I was attempting to use this for load balancing but it didn't work out. - Define a kseq_print() for use with debugging. - Add KTR debugging at useful places so we can easily debug slice and priority assignment. - Decouple the runq assignment from the kseq assignment. kseq_add now keeps track of statistics. This is done so that the nice and load is still tracked for the currently running process. Previously if a niced process was added while a non nice process was running the niced process would still get a slice since it was not aware of the unnice process. - Make adjustments for the sched api changes.
2003-04-11 03:47:14 +00:00
*/
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
int
sched_rr_interval(void)
{
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
Some minor tunings/cleanups inspired by bde@ after previous commits: - remove extra dynamic variable initializations; - restore (4BSD) and implement (ULE) hogticks variable setting; - make sched_rr_interval() more tolerant to options; - restore (4BSD) and implement (ULE) kern.sched.quantum sysctl, a more user-friendly wrapper for sched_slice; - tune some sysctl descriptions; - make some style fixes.
2012-08-10 19:02:49 +00:00
/* Convert sched_slice from stathz to hz. */
Some more minor tunings inspired by bde@.
2012-08-11 20:24:39 +00:00
return (imax(1, (sched_slice * hz + realstathz / 2) / realstathz));
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
}
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* Update the percent cpu tracking information when it is requested or
* the total history exceeds the maximum. We keep a sliding history of
* tick counts that slowly decays. This is less precise than the 4BSD
* mechanism since it happens with less regular and frequent events.
*/
- Add static to local functions and data where it was missing. - Add an IPI based mechanism for migrating kses. This mechanism is broken down into several components. This is intended to reduce cache thrashing by eliminating most cases where one cpu touches another's run queues. - kseq_notify() appends a kse to a lockless singly linked list and conditionally sends an IPI to the target processor. Right now this is protected by sched_lock but at some point I'd like to get rid of the global lock. This is why I used something more complicated than a standard queue. - kseq_assign() processes our list of kses that have been assigned to us by other processors. This simply calls sched_add() for each item on the list after clearing the new KEF_ASSIGNED flag. This flag is used to indicate that we have been appeneded to the assigned queue but not added to the run queue yet. - In sched_add(), instead of adding a KSE to another processor's queue we use kse_notify() so that we don't touch their queue. Also in sched_add(), if KEF_ASSIGNED is already set return immediately. This can happen if a thread is removed and readded so that the priority is recorded properly. - In sched_rem() return immediately if KEF_ASSIGNED is set. All callers immediately readd simply to adjust priorites etc. - In sched_choose(), if we're running an IDLE task or the per cpu idle thread set our cpumask bit in 'kseq_idle' so that other processors may know that we are idle. Before this, make a single pass through the run queues of other processors so that we may find work more immediately if it is available. - In sched_runnable(), don't scan each processor's run queue, they will IPI us if they have work for us to do. - In sched_add(), if we're adding a thread that can be migrated and we have plenty of work to do, try to migrate the thread to an idle kseq. - Simplify the logic in sched_prio() and take the KEF_ASSIGNED flag into consideration. - No longer use kseq_choose() to steal threads, it can lose it's last argument. - Create a new function runq_steal() which operates like runq_choose() but skips threads based on some criteria. Currently it will not steal PRI_ITHD threads. In the future this will be used for CPU binding. - Create a kseq_steal() that checks each run queue with runq_steal(), use kseq_steal() in the places where we used kseq_choose() to steal with before.
2003-10-31 11:16:04 +00:00
static void
Rewrite thread CPU usage percentage math to not depend on periodic calls with HZ rate through the sched_tick() calls from hardclock(). Potentially it can be used to improve precision, but now it is just minus one more reason to call hardclock() for every HZ tick on every active CPU. SCHED_4BSD never used sched_tick(), but keep it in place for now, as at least SCHED_FBFS existing in patches out of the tree depends on it. MFC after: 1 month
2012-03-13 08:18:54 +00:00
sched_pctcpu_update(struct td_sched *ts, int run)
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
{
Rewrite thread CPU usage percentage math to not depend on periodic calls with HZ rate through the sched_tick() calls from hardclock(). Potentially it can be used to improve precision, but now it is just minus one more reason to call hardclock() for every HZ tick on every active CPU. SCHED_4BSD never used sched_tick(), but keep it in place for now, as at least SCHED_FBFS existing in patches out of the tree depends on it. MFC after: 1 month
2012-03-13 08:18:54 +00:00
int t = ticks;
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
Fix a ticks comparison in sched_pctcpu_update(). We may fail to reset the %CPU tracking window if a thread does not run for over half of the ticks rollover period, resulting in a bogus %CPU value for the thread until ticks fully rolls over. Handle this by comparing the unsigned difference ticks - ts_ltick with SCHED_TICK_TARG instead. Reviewed by: cem, jeff MFC after: 1 week Sponsored by: Dell EMC Isilon
2017-03-03 20:57:40 +00:00
/*
* The signed difference may be negative if the thread hasn't run for
* over half of the ticks rollover period.
*/
if ((u_int)(t - ts->ts_ltick) >= SCHED_TICK_TARG) {
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
ts->ts_ticks = 0;
Rewrite thread CPU usage percentage math to not depend on periodic calls with HZ rate through the sched_tick() calls from hardclock(). Potentially it can be used to improve precision, but now it is just minus one more reason to call hardclock() for every HZ tick on every active CPU. SCHED_4BSD never used sched_tick(), but keep it in place for now, as at least SCHED_FBFS existing in patches out of the tree depends on it. MFC after: 1 month
2012-03-13 08:18:54 +00:00
ts->ts_ftick = t - SCHED_TICK_TARG;
} else if (t - ts->ts_ftick >= SCHED_TICK_MAX) {
ts->ts_ticks = (ts->ts_ticks / (ts->ts_ltick - ts->ts_ftick)) *
(ts->ts_ltick - (t - SCHED_TICK_TARG));
ts->ts_ftick = t - SCHED_TICK_TARG;
}
if (run)
ts->ts_ticks += (t - ts->ts_ltick) << SCHED_TICK_SHIFT;
ts->ts_ltick = t;
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
}
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* Adjust the priority of a thread. Move it to the appropriate run-queue
* if necessary. This is the back-end for several priority related
* functions.
*/
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
static void
Rework the interface between priority propagation (lending) and the schedulers a bit to ensure more correct handling of priorities and fewer priority inversions: - Add two functions to the sched(9) API to handle priority lending: sched_lend_prio() and sched_unlend_prio(). The turnstile code uses these functions to ask the scheduler to lend a thread a set priority and to tell the scheduler when it thinks it is ok for a thread to stop borrowing priority. The unlend case is slightly complex in that the turnstile code tells the scheduler what the minimum priority of the thread needs to be to satisfy the requirements of any other threads blocked on locks owned by the thread in question. The scheduler then decides where the thread can go back to normal mode (if it's normal priority is high enough to satisfy the pending lock requests) or it it should continue to use the priority specified to the sched_unlend_prio() call. This involves adding a new per-thread flag TDF_BORROWING that replaces the ULE-only kse flag for priority elevation. - Schedulers now refuse to lower the priority of a thread that is currently borrowing another therad's priority. - If a scheduler changes the priority of a thread that is currently sitting on a turnstile, it will call a new function turnstile_adjust() to inform the turnstile code of the change. This function resorts the thread on the priority list of the turnstile if needed, and if the thread ends up at the head of the list (due to having the highest priority) and its priority was raised, then it will propagate that new priority to the owner of the lock it is blocked on. Some additional fixes specific to the 4BSD scheduler include: - Common code for updating the priority of a thread when the user priority of its associated kse group has been consolidated in a new static function resetpriority_thread(). One change to this function is that it will now only adjust the priority of a thread if it already has a time sharing priority, thus preserving any boosts from a tsleep() until the thread returns to userland. Also, resetpriority() no longer calls maybe_resched() on each thread in the group. Instead, the code calling resetpriority() is responsible for calling resetpriority_thread() on any threads that need to be updated. - schedcpu() now uses resetpriority_thread() instead of just calling sched_prio() directly after it updates a kse group's user priority. - sched_clock() now uses resetpriority_thread() rather than writing directly to td_priority. - sched_nice() now updates all the priorities of the threads after the group priority has been adjusted. Discussed with: bde Reviewed by: ups, jeffr Tested on: 4bsd, ule Tested on: i386, alpha, sparc64
2004-12-30 20:52:44 +00:00
sched_thread_priority(struct thread *td, u_char prio)
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
{
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
struct td_sched *ts;
Reduce ULE context switch time by over 25%. - Only calculate timeshare priorities once per tick or when a thread is woken from sleeping. - Keep the ts_runq pointer valid after all priority changes. - Call tdq_runq_add() directly from sched_switch() without passing in via tdq_add(). We don't need to adjust loads or runqs anymore. - Sort tdq and ts_sched according to utilization to improve cache behavior. Sponsored by: Nokia
2008-03-10 03:15:19 +00:00
struct tdq *tdq;
int oldpri;
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
- Implement generic macros for producing KTR records that are compatible with src/tools/sched/schedgraph.py. This allows developers to quickly create a graphical view of ktr data for any resource in the system. - Add sched_tdname() and the pcpu field 'name' for quickly and uniformly identifying records associated with a thread or cpu. - Reimplement the KTR_SCHED traces using the new generic facility. Obtained from: attilio Discussed with: jhb Sponsored by: Nokia
2009-01-17 07:17:57 +00:00
KTR_POINT3(KTR_SCHED, "thread", sched_tdname(td), "prio",
"prio:%d", td->td_priority, "new prio:%d", prio,
KTR_ATTR_LINKED, sched_tdname(curthread));
dtrace sdt: remove the ugly sname parameter of SDT_PROBE_DEFINE In its stead use the Solaris / illumos approach of emulating '-' (dash) in probe names with '__' (two consecutive underscores). Reviewed by: markj MFC after: 3 weeks
2013-11-26 08:46:27 +00:00
SDT_PROBE3(sched, , , change__pri, td, td->td_proc, prio);
sched_ule: fix inverted condition in reporting of priority lending via ktr Reviewed by: kan MFC after: 1 week
2012-09-14 19:55:28 +00:00
if (td != curthread && prio < td->td_priority) {
- Implement generic macros for producing KTR records that are compatible with src/tools/sched/schedgraph.py. This allows developers to quickly create a graphical view of ktr data for any resource in the system. - Add sched_tdname() and the pcpu field 'name' for quickly and uniformly identifying records associated with a thread or cpu. - Reimplement the KTR_SCHED traces using the new generic facility. Obtained from: attilio Discussed with: jhb Sponsored by: Nokia
2009-01-17 07:17:57 +00:00
KTR_POINT3(KTR_SCHED, "thread", sched_tdname(curthread),
"lend prio", "prio:%d", td->td_priority, "new prio:%d",
prio, KTR_ATTR_LINKED, sched_tdname(td));
dtrace sdt: remove the ugly sname parameter of SDT_PROBE_DEFINE In its stead use the Solaris / illumos approach of emulating '-' (dash) in probe names with '__' (two consecutive underscores). Reviewed by: markj MFC after: 3 weeks
2013-11-26 08:46:27 +00:00
SDT_PROBE4(sched, , , lend__pri, td, td->td_proc, prio,
Implement the DTrace sched provider. This implementation aims to be compatible with the sched provider implemented by Solaris and its open- source derivatives. Full documentation of the sched provider can be found on Oracle's DTrace wiki pages. Note that for compatibility with scripts originally written for Solaris, serveral probes are defined that will never fire. These probes are defined to fire when Solaris-specific features perform certain actions. As these features are not present in FreeBSD, the probes can never fire. Also, I have added a two probes that are not defined in Solaris, lend-pri and load-change. These probes have been added to make it possible to collect schedgraph data with DTrace. Finally, a few probes are defined in Solaris to take a cpuinfo_t * argument. As it was not immediately clear to me how to translate that to FreeBSD, currently those probes are passed NULL in place of a cpuinfo_t *. Sponsored by: Sandvine Incorporated MFC after: 2 weeks
2012-05-15 01:30:25 +00:00
curthread);
- Implement generic macros for producing KTR records that are compatible with src/tools/sched/schedgraph.py. This allows developers to quickly create a graphical view of ktr data for any resource in the system. - Add sched_tdname() and the pcpu field 'name' for quickly and uniformly identifying records associated with a thread or cpu. - Reimplement the KTR_SCHED traces using the new generic facility. Obtained from: attilio Discussed with: jhb Sponsored by: Nokia
2009-01-17 07:17:57 +00:00
}
Get rid of struct proc p_sched and struct thread td_sched pointers. p_sched is unused. The struct td_sched is always co-allocated with the struct thread, except for the thread0. Avoid useless indirection, instead calculate td_sched location using simple pointer arithmetic in td_get_sched(9). For thread0, which is statically allocated, create a structure to emulate layout of the dynamic allocation. Reviewed by: jhb (previous version) Sponsored by: The FreeBSD Foundation Differential revision: https://reviews.freebsd.org/D6711
2016-06-05 17:04:03 +00:00
ts = td_get_sched(td);
Commit 1/14 of sched_lock decomposition. - Move all scheduler locking into the schedulers utilizing a technique similar to solaris's container locking. - A per-process spinlock is now used to protect the queue of threads, thread count, suspension count, p_sflags, and other process related scheduling fields. - The new thread lock is actually a pointer to a spinlock for the container that the thread is currently owned by. The container may be a turnstile, sleepqueue, or run queue. - thread_lock() is now used to protect access to thread related scheduling fields. thread_unlock() unlocks the lock and thread_set_lock() implements the transition from one lock to another. - A new "blocked_lock" is used in cases where it is not safe to hold the actual thread's lock yet we must prevent access to the thread. - sched_throw() and sched_fork_exit() are introduced to allow the schedulers to fix-up locking at these points. - Add some minor infrastructure for optionally exporting scheduler statistics that were invaluable in solving performance problems with this patch. Generally these statistics allow you to differentiate between different causes of context switches. Tested by: kris, current@ Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc. Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:50:30 +00:00
THREAD_LOCK_ASSERT(td, MA_OWNED);
Rework the interface between priority propagation (lending) and the schedulers a bit to ensure more correct handling of priorities and fewer priority inversions: - Add two functions to the sched(9) API to handle priority lending: sched_lend_prio() and sched_unlend_prio(). The turnstile code uses these functions to ask the scheduler to lend a thread a set priority and to tell the scheduler when it thinks it is ok for a thread to stop borrowing priority. The unlend case is slightly complex in that the turnstile code tells the scheduler what the minimum priority of the thread needs to be to satisfy the requirements of any other threads blocked on locks owned by the thread in question. The scheduler then decides where the thread can go back to normal mode (if it's normal priority is high enough to satisfy the pending lock requests) or it it should continue to use the priority specified to the sched_unlend_prio() call. This involves adding a new per-thread flag TDF_BORROWING that replaces the ULE-only kse flag for priority elevation. - Schedulers now refuse to lower the priority of a thread that is currently borrowing another therad's priority. - If a scheduler changes the priority of a thread that is currently sitting on a turnstile, it will call a new function turnstile_adjust() to inform the turnstile code of the change. This function resorts the thread on the priority list of the turnstile if needed, and if the thread ends up at the head of the list (due to having the highest priority) and its priority was raised, then it will propagate that new priority to the owner of the lock it is blocked on. Some additional fixes specific to the 4BSD scheduler include: - Common code for updating the priority of a thread when the user priority of its associated kse group has been consolidated in a new static function resetpriority_thread(). One change to this function is that it will now only adjust the priority of a thread if it already has a time sharing priority, thus preserving any boosts from a tsleep() until the thread returns to userland. Also, resetpriority() no longer calls maybe_resched() on each thread in the group. Instead, the code calling resetpriority() is responsible for calling resetpriority_thread() on any threads that need to be updated. - schedcpu() now uses resetpriority_thread() instead of just calling sched_prio() directly after it updates a kse group's user priority. - sched_clock() now uses resetpriority_thread() rather than writing directly to td_priority. - sched_nice() now updates all the priorities of the threads after the group priority has been adjusted. Discussed with: bde Reviewed by: ups, jeffr Tested on: 4bsd, ule Tested on: i386, alpha, sparc64
2004-12-30 20:52:44 +00:00
if (td->td_priority == prio)
return;
- Remove some dead code and comments related to KSE. - Don't set tdq_lowpri on every switch, it should be precisely maintained now. - Add some comments to sched_thread_priority().
2008-03-19 07:36:37 +00:00
/*
* If the priority has been elevated due to priority
* propagation, we may have to move ourselves to a new
* queue. This could be optimized to not re-add in some
* cases.
*/
- Only allow the tdq_idx to increase by one each tick rather than up to the most recently chosen index. This significantly improves nice behavior. This allows a lower priority thread to run some multiple of times before the higher priority thread makes it to the front of the queue. A nice +20 cpu hog now only gets ~5% of the cpu when running with a nice 0 cpu hog and about 1.5% with a nice -20 hog. A nice difference of 1 makes a 4% difference in cpu usage between two hogs. - Track a seperate insert and removal index. When the removal index is empty it is updated to point at the current insert index. - Don't remove and re-add a thread to the runq when it is being adjusted down in priority. - Pull some conditional code out of sched_tick(). It's looking a bit large now.
2007-01-04 12:16:19 +00:00
if (TD_ON_RUNQ(td) && prio < td->td_priority) {
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
sched_rem(td);
td->td_priority = prio;
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
sched_add(td, SRQ_BORROWING);
Reduce ULE context switch time by over 25%. - Only calculate timeshare priorities once per tick or when a thread is woken from sleeping. - Keep the ts_runq pointer valid after all priority changes. - Call tdq_runq_add() directly from sched_switch() without passing in via tdq_add(). We don't need to adjust loads or runqs anymore. - Sort tdq and ts_sched according to utilization to improve cache behavior. Sponsored by: Nokia
2008-03-10 03:15:19 +00:00
return;
}
- Remove some dead code and comments related to KSE. - Don't set tdq_lowpri on every switch, it should be precisely maintained now. - Add some comments to sched_thread_priority().
2008-03-19 07:36:37 +00:00
/*
* If the thread is currently running we may have to adjust the lowpri
* information so other cpus are aware of our current priority.
*/
Reduce ULE context switch time by over 25%. - Only calculate timeshare priorities once per tick or when a thread is woken from sleeping. - Keep the ts_runq pointer valid after all priority changes. - Call tdq_runq_add() directly from sched_switch() without passing in via tdq_add(). We don't need to adjust loads or runqs anymore. - Sort tdq and ts_sched according to utilization to improve cache behavior. Sponsored by: Nokia
2008-03-10 03:15:19 +00:00
if (TD_IS_RUNNING(td)) {
- Remove some dead code and comments related to KSE. - Don't set tdq_lowpri on every switch, it should be precisely maintained now. - Add some comments to sched_thread_priority().
2008-03-19 07:36:37 +00:00
tdq = TDQ_CPU(ts->ts_cpu);
oldpri = td->td_priority;
td->td_priority = prio;
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
if (prio < tdq->tdq_lowpri)
tdq->tdq_lowpri = prio;
else if (tdq->tdq_lowpri == oldpri)
tdq_setlowpri(tdq, td);
- Remove some dead code and comments related to KSE. - Don't set tdq_lowpri on every switch, it should be precisely maintained now. - Add some comments to sched_thread_priority().
2008-03-19 07:36:37 +00:00
return;
Reduce ULE context switch time by over 25%. - Only calculate timeshare priorities once per tick or when a thread is woken from sleeping. - Keep the ts_runq pointer valid after all priority changes. - Call tdq_runq_add() directly from sched_switch() without passing in via tdq_add(). We don't need to adjust loads or runqs anymore. - Sort tdq and ts_sched according to utilization to improve cache behavior. Sponsored by: Nokia
2008-03-10 03:15:19 +00:00
}
- Remove some dead code and comments related to KSE. - Don't set tdq_lowpri on every switch, it should be precisely maintained now. - Add some comments to sched_thread_priority().
2008-03-19 07:36:37 +00:00
td->td_priority = prio;
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
}
Rework the interface between priority propagation (lending) and the schedulers a bit to ensure more correct handling of priorities and fewer priority inversions: - Add two functions to the sched(9) API to handle priority lending: sched_lend_prio() and sched_unlend_prio(). The turnstile code uses these functions to ask the scheduler to lend a thread a set priority and to tell the scheduler when it thinks it is ok for a thread to stop borrowing priority. The unlend case is slightly complex in that the turnstile code tells the scheduler what the minimum priority of the thread needs to be to satisfy the requirements of any other threads blocked on locks owned by the thread in question. The scheduler then decides where the thread can go back to normal mode (if it's normal priority is high enough to satisfy the pending lock requests) or it it should continue to use the priority specified to the sched_unlend_prio() call. This involves adding a new per-thread flag TDF_BORROWING that replaces the ULE-only kse flag for priority elevation. - Schedulers now refuse to lower the priority of a thread that is currently borrowing another therad's priority. - If a scheduler changes the priority of a thread that is currently sitting on a turnstile, it will call a new function turnstile_adjust() to inform the turnstile code of the change. This function resorts the thread on the priority list of the turnstile if needed, and if the thread ends up at the head of the list (due to having the highest priority) and its priority was raised, then it will propagate that new priority to the owner of the lock it is blocked on. Some additional fixes specific to the 4BSD scheduler include: - Common code for updating the priority of a thread when the user priority of its associated kse group has been consolidated in a new static function resetpriority_thread(). One change to this function is that it will now only adjust the priority of a thread if it already has a time sharing priority, thus preserving any boosts from a tsleep() until the thread returns to userland. Also, resetpriority() no longer calls maybe_resched() on each thread in the group. Instead, the code calling resetpriority() is responsible for calling resetpriority_thread() on any threads that need to be updated. - schedcpu() now uses resetpriority_thread() instead of just calling sched_prio() directly after it updates a kse group's user priority. - sched_clock() now uses resetpriority_thread() rather than writing directly to td_priority. - sched_nice() now updates all the priorities of the threads after the group priority has been adjusted. Discussed with: bde Reviewed by: ups, jeffr Tested on: 4bsd, ule Tested on: i386, alpha, sparc64
2004-12-30 20:52:44 +00:00
/*
* Update a thread's priority when it is lent another thread's
* priority.
*/
void
sched_lend_prio(struct thread *td, u_char prio)
{
td->td_flags |= TDF_BORROWING;
sched_thread_priority(td, prio);
}
/*
* Restore a thread's priority when priority propagation is
* over. The prio argument is the minimum priority the thread
* needs to have to satisfy other possible priority lending
* requests. If the thread's regular priority is less
* important than prio, the thread will keep a priority boost
* of prio.
*/
void
sched_unlend_prio(struct thread *td, u_char prio)
{
u_char base_pri;
if (td->td_base_pri >= PRI_MIN_TIMESHARE &&
td->td_base_pri <= PRI_MAX_TIMESHARE)
Make KSE a kernel option, turned on by default in all GENERIC kernel configs except sun4v (which doesn't process signals properly with KSE). Reviewed by: davidxu@
2006-10-26 21:42:22 +00:00
base_pri = td->td_user_pri;
Rework the interface between priority propagation (lending) and the schedulers a bit to ensure more correct handling of priorities and fewer priority inversions: - Add two functions to the sched(9) API to handle priority lending: sched_lend_prio() and sched_unlend_prio(). The turnstile code uses these functions to ask the scheduler to lend a thread a set priority and to tell the scheduler when it thinks it is ok for a thread to stop borrowing priority. The unlend case is slightly complex in that the turnstile code tells the scheduler what the minimum priority of the thread needs to be to satisfy the requirements of any other threads blocked on locks owned by the thread in question. The scheduler then decides where the thread can go back to normal mode (if it's normal priority is high enough to satisfy the pending lock requests) or it it should continue to use the priority specified to the sched_unlend_prio() call. This involves adding a new per-thread flag TDF_BORROWING that replaces the ULE-only kse flag for priority elevation. - Schedulers now refuse to lower the priority of a thread that is currently borrowing another therad's priority. - If a scheduler changes the priority of a thread that is currently sitting on a turnstile, it will call a new function turnstile_adjust() to inform the turnstile code of the change. This function resorts the thread on the priority list of the turnstile if needed, and if the thread ends up at the head of the list (due to having the highest priority) and its priority was raised, then it will propagate that new priority to the owner of the lock it is blocked on. Some additional fixes specific to the 4BSD scheduler include: - Common code for updating the priority of a thread when the user priority of its associated kse group has been consolidated in a new static function resetpriority_thread(). One change to this function is that it will now only adjust the priority of a thread if it already has a time sharing priority, thus preserving any boosts from a tsleep() until the thread returns to userland. Also, resetpriority() no longer calls maybe_resched() on each thread in the group. Instead, the code calling resetpriority() is responsible for calling resetpriority_thread() on any threads that need to be updated. - schedcpu() now uses resetpriority_thread() instead of just calling sched_prio() directly after it updates a kse group's user priority. - sched_clock() now uses resetpriority_thread() rather than writing directly to td_priority. - sched_nice() now updates all the priorities of the threads after the group priority has been adjusted. Discussed with: bde Reviewed by: ups, jeffr Tested on: 4bsd, ule Tested on: i386, alpha, sparc64
2004-12-30 20:52:44 +00:00
else
base_pri = td->td_base_pri;
if (prio >= base_pri) {
Fix a typo and two whitespace nits.
2004-12-30 22:17:00 +00:00
td->td_flags &= ~TDF_BORROWING;
Rework the interface between priority propagation (lending) and the schedulers a bit to ensure more correct handling of priorities and fewer priority inversions: - Add two functions to the sched(9) API to handle priority lending: sched_lend_prio() and sched_unlend_prio(). The turnstile code uses these functions to ask the scheduler to lend a thread a set priority and to tell the scheduler when it thinks it is ok for a thread to stop borrowing priority. The unlend case is slightly complex in that the turnstile code tells the scheduler what the minimum priority of the thread needs to be to satisfy the requirements of any other threads blocked on locks owned by the thread in question. The scheduler then decides where the thread can go back to normal mode (if it's normal priority is high enough to satisfy the pending lock requests) or it it should continue to use the priority specified to the sched_unlend_prio() call. This involves adding a new per-thread flag TDF_BORROWING that replaces the ULE-only kse flag for priority elevation. - Schedulers now refuse to lower the priority of a thread that is currently borrowing another therad's priority. - If a scheduler changes the priority of a thread that is currently sitting on a turnstile, it will call a new function turnstile_adjust() to inform the turnstile code of the change. This function resorts the thread on the priority list of the turnstile if needed, and if the thread ends up at the head of the list (due to having the highest priority) and its priority was raised, then it will propagate that new priority to the owner of the lock it is blocked on. Some additional fixes specific to the 4BSD scheduler include: - Common code for updating the priority of a thread when the user priority of its associated kse group has been consolidated in a new static function resetpriority_thread(). One change to this function is that it will now only adjust the priority of a thread if it already has a time sharing priority, thus preserving any boosts from a tsleep() until the thread returns to userland. Also, resetpriority() no longer calls maybe_resched() on each thread in the group. Instead, the code calling resetpriority() is responsible for calling resetpriority_thread() on any threads that need to be updated. - schedcpu() now uses resetpriority_thread() instead of just calling sched_prio() directly after it updates a kse group's user priority. - sched_clock() now uses resetpriority_thread() rather than writing directly to td_priority. - sched_nice() now updates all the priorities of the threads after the group priority has been adjusted. Discussed with: bde Reviewed by: ups, jeffr Tested on: 4bsd, ule Tested on: i386, alpha, sparc64
2004-12-30 20:52:44 +00:00
sched_thread_priority(td, base_pri);
} else
sched_lend_prio(td, prio);
}
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* Standard entry for setting the priority to an absolute value.
*/
Rework the interface between priority propagation (lending) and the schedulers a bit to ensure more correct handling of priorities and fewer priority inversions: - Add two functions to the sched(9) API to handle priority lending: sched_lend_prio() and sched_unlend_prio(). The turnstile code uses these functions to ask the scheduler to lend a thread a set priority and to tell the scheduler when it thinks it is ok for a thread to stop borrowing priority. The unlend case is slightly complex in that the turnstile code tells the scheduler what the minimum priority of the thread needs to be to satisfy the requirements of any other threads blocked on locks owned by the thread in question. The scheduler then decides where the thread can go back to normal mode (if it's normal priority is high enough to satisfy the pending lock requests) or it it should continue to use the priority specified to the sched_unlend_prio() call. This involves adding a new per-thread flag TDF_BORROWING that replaces the ULE-only kse flag for priority elevation. - Schedulers now refuse to lower the priority of a thread that is currently borrowing another therad's priority. - If a scheduler changes the priority of a thread that is currently sitting on a turnstile, it will call a new function turnstile_adjust() to inform the turnstile code of the change. This function resorts the thread on the priority list of the turnstile if needed, and if the thread ends up at the head of the list (due to having the highest priority) and its priority was raised, then it will propagate that new priority to the owner of the lock it is blocked on. Some additional fixes specific to the 4BSD scheduler include: - Common code for updating the priority of a thread when the user priority of its associated kse group has been consolidated in a new static function resetpriority_thread(). One change to this function is that it will now only adjust the priority of a thread if it already has a time sharing priority, thus preserving any boosts from a tsleep() until the thread returns to userland. Also, resetpriority() no longer calls maybe_resched() on each thread in the group. Instead, the code calling resetpriority() is responsible for calling resetpriority_thread() on any threads that need to be updated. - schedcpu() now uses resetpriority_thread() instead of just calling sched_prio() directly after it updates a kse group's user priority. - sched_clock() now uses resetpriority_thread() rather than writing directly to td_priority. - sched_nice() now updates all the priorities of the threads after the group priority has been adjusted. Discussed with: bde Reviewed by: ups, jeffr Tested on: 4bsd, ule Tested on: i386, alpha, sparc64
2004-12-30 20:52:44 +00:00
void
sched_prio(struct thread *td, u_char prio)
{
u_char oldprio;
/* First, update the base priority. */
td->td_base_pri = prio;
/*
Fix a typo and two whitespace nits.
2004-12-30 22:17:00 +00:00
* If the thread is borrowing another thread's priority, don't
Rework the interface between priority propagation (lending) and the schedulers a bit to ensure more correct handling of priorities and fewer priority inversions: - Add two functions to the sched(9) API to handle priority lending: sched_lend_prio() and sched_unlend_prio(). The turnstile code uses these functions to ask the scheduler to lend a thread a set priority and to tell the scheduler when it thinks it is ok for a thread to stop borrowing priority. The unlend case is slightly complex in that the turnstile code tells the scheduler what the minimum priority of the thread needs to be to satisfy the requirements of any other threads blocked on locks owned by the thread in question. The scheduler then decides where the thread can go back to normal mode (if it's normal priority is high enough to satisfy the pending lock requests) or it it should continue to use the priority specified to the sched_unlend_prio() call. This involves adding a new per-thread flag TDF_BORROWING that replaces the ULE-only kse flag for priority elevation. - Schedulers now refuse to lower the priority of a thread that is currently borrowing another therad's priority. - If a scheduler changes the priority of a thread that is currently sitting on a turnstile, it will call a new function turnstile_adjust() to inform the turnstile code of the change. This function resorts the thread on the priority list of the turnstile if needed, and if the thread ends up at the head of the list (due to having the highest priority) and its priority was raised, then it will propagate that new priority to the owner of the lock it is blocked on. Some additional fixes specific to the 4BSD scheduler include: - Common code for updating the priority of a thread when the user priority of its associated kse group has been consolidated in a new static function resetpriority_thread(). One change to this function is that it will now only adjust the priority of a thread if it already has a time sharing priority, thus preserving any boosts from a tsleep() until the thread returns to userland. Also, resetpriority() no longer calls maybe_resched() on each thread in the group. Instead, the code calling resetpriority() is responsible for calling resetpriority_thread() on any threads that need to be updated. - schedcpu() now uses resetpriority_thread() instead of just calling sched_prio() directly after it updates a kse group's user priority. - sched_clock() now uses resetpriority_thread() rather than writing directly to td_priority. - sched_nice() now updates all the priorities of the threads after the group priority has been adjusted. Discussed with: bde Reviewed by: ups, jeffr Tested on: 4bsd, ule Tested on: i386, alpha, sparc64
2004-12-30 20:52:44 +00:00
* ever lower the priority.
*/
if (td->td_flags & TDF_BORROWING && td->td_priority < prio)
return;
/* Change the real priority. */
oldprio = td->td_priority;
sched_thread_priority(td, prio);
/*
* If the thread is on a turnstile, then let the turnstile update
* its state.
*/
if (TD_ON_LOCK(td) && oldprio != prio)
turnstile_adjust(td, oldprio);
}
Fix a typo and two whitespace nits.
2004-12-30 22:17:00 +00:00
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* Set the base user priority, does not effect current running priority.
*/
Add user priority loaning code to support priority propagation for 1:1 threading's POSIX priority mutexes, the code is no-op unless priority-aware umtx code is committed.
2006-08-25 06:12:53 +00:00
void
Make KSE a kernel option, turned on by default in all GENERIC kernel configs except sun4v (which doesn't process signals properly with KSE). Reviewed by: davidxu@
2006-10-26 21:42:22 +00:00
sched_user_prio(struct thread *td, u_char prio)
Add user priority loaning code to support priority propagation for 1:1 threading's POSIX priority mutexes, the code is no-op unless priority-aware umtx code is committed.
2006-08-25 06:12:53 +00:00
{
Make KSE a kernel option, turned on by default in all GENERIC kernel configs except sun4v (which doesn't process signals properly with KSE). Reviewed by: davidxu@
2006-10-26 21:42:22 +00:00
td->td_base_user_pri = prio;
MFp4: It is possible a lower priority thread lending priority to higher priority thread, in old code, it is ignored, however the lending should always be recorded, add field td_lend_user_pri to fix the problem, if a thread does not have borrowed priority, its value is PRI_MAX. MFC after: 1 week
2010-12-09 02:42:02 +00:00
if (td->td_lend_user_pri <= prio)
return;
Make KSE a kernel option, turned on by default in all GENERIC kernel configs except sun4v (which doesn't process signals properly with KSE). Reviewed by: davidxu@
2006-10-26 21:42:22 +00:00
td->td_user_pri = prio;
Add user priority loaning code to support priority propagation for 1:1 threading's POSIX priority mutexes, the code is no-op unless priority-aware umtx code is committed.
2006-08-25 06:12:53 +00:00
}
void
sched_lend_user_prio(struct thread *td, u_char prio)
{
Fix LOR of thread lock and umtx's priority propagation mutex due to the reworking of scheduler lock. MFC: after 3 days
2007-12-11 08:25:36 +00:00
THREAD_LOCK_ASSERT(td, MA_OWNED);
MFp4: It is possible a lower priority thread lending priority to higher priority thread, in old code, it is ignored, however the lending should always be recorded, add field td_lend_user_pri to fix the problem, if a thread does not have borrowed priority, its value is PRI_MAX. MFC after: 1 week
2010-12-09 02:42:02 +00:00
td->td_lend_user_pri = prio;
- Follow r216313, the sched_unlend_user_prio is no longer needed, always use sched_lend_user_prio to set lent priority. - Improve pthread priority-inherit mutex, when a contender's priority is lowered, repropagete priorities, this may cause mutex owner's priority to be lowerd, in old code, mutex owner's priority is rise-only.
2010-12-29 09:26:46 +00:00
td->td_user_pri = min(prio, td->td_base_user_pri);
if (td->td_priority > td->td_user_pri)
sched_prio(td, td->td_user_pri);
else if (td->td_priority != td->td_user_pri)
td->td_flags |= TDF_NEEDRESCHED;
Add user priority loaning code to support priority propagation for 1:1 threading's POSIX priority mutexes, the code is no-op unless priority-aware umtx code is committed.
2006-08-25 06:12:53 +00:00
}
Restore UP build. Reviewed by: truckman Sponsored by: The FreeBSD Foundation
2018-02-23 18:26:31 +00:00
#ifdef SMP
Decrease latency by not wrapping the idle loop's potentially lengthy search for a thread to steal inside a critical section. Since this allows the search to be preempted, restart the search if preemption happens since the search results found earlier may no longer be valid. Decrease the latency of starting a thread that may be assigned to this CPU during the search by polling for incoming threads during the search and switching to that thread instead of continuing the search. Test for stale search results and restart the search before going through the expense of calling tdq_lock_pair(). Retry some tests after grabbing the locks since things may have changed while waiting to get both locks. Eliminate special case handling for stealing from an SMT peer that uses 1 as the steal threshold. This can only succeed if a thread has been assigned but our SMT peer has not yet started executing it. This is quite rare and when it happens the other SMT thread is generally waiting for the same tdq lock that we hold. Basically both SMT threads are racing to grab the same spin lock. Add the kern.sched.always_steal knob from a ULE patch by jeff@. Incorporate another idea from Jeff's ULE patch. If the sched_switch() detects that the CPU is about to go idle, try to steal a thread before switching to the idle thread. Since the search for a thread to steal has to be done inside a critical section in this context, limit the impact on latency by adding the knob kern.sched.trysteal_limit to limit the topological distance of the search and don't restart the search if we detect stale results. If this search can't find an stealable thread, the idle loop can do a more complete search. Also poll for threads being assigned to this CPU during the search and switch to them instead of continuing the search. This change is responsibile for the majority of the improvement in parallel buildworld times. In sched_balance_group() change the minimum threshold from stealing a thread from 1 to 2. Poaching a newly assigned thread from a CPU that is waking up hasn't yet switched to that thread from idle is likely very rare and is likely to have the same lock race as is seen when stealing threads in the idle loop. Also use tdq_notify() to kick the destintation CPU instead of always sending an IPI. Update a stale comment, the number of transferable threads is not calculated. Reviewed by: kib (earlier version) Comments by: avg, jeff, mav MFC after: 1 month Differential Revision: https://reviews.freebsd.org/D12130
2018-02-23 00:12:51 +00:00
/*
* This tdq is about to idle. Try to steal a thread from another CPU before
* choosing the idle thread.
*/
static void
tdq_trysteal(struct tdq *tdq)
{
struct cpu_group *cg;
struct tdq *steal;
cpuset_t mask;
int cpu, i;
if (smp_started == 0 || trysteal_limit == 0 || tdq->tdq_cg == NULL)
return;
CPU_FILL(&mask);
CPU_CLR(PCPU_GET(cpuid), &mask);
/* We don't want to be preempted while we're iterating. */
spinlock_enter();
TDQ_UNLOCK(tdq);
for (i = 1, cg = tdq->tdq_cg; ; ) {
cpu = sched_highest(cg, mask, steal_thresh);
/*
* If a thread was added while interrupts were disabled don't
* steal one here.
*/
if (tdq->tdq_load > 0) {
TDQ_LOCK(tdq);
break;
}
if (cpu == -1) {
i++;
cg = cg->cg_parent;
if (cg == NULL || i > trysteal_limit) {
TDQ_LOCK(tdq);
break;
}
continue;
}
steal = TDQ_CPU(cpu);
/*
* The data returned by sched_highest() is stale and
* the chosen CPU no longer has an eligible thread.
*/
if (steal->tdq_load < steal_thresh ||
steal->tdq_transferable == 0)
continue;
tdq_lock_pair(tdq, steal);
/*
* If we get to this point, unconditonally exit the loop
* to bound the time spent in the critcal section.
*
* If a thread was added while interrupts were disabled don't
* steal one here.
*/
if (tdq->tdq_load > 0) {
TDQ_UNLOCK(steal);
break;
}
/*
* The data returned by sched_highest() is stale and
* the chosen CPU no longer has an eligible thread.
*/
if (steal->tdq_load < steal_thresh ||
steal->tdq_transferable == 0) {
TDQ_UNLOCK(steal);
break;
}
/*
* If we fail to acquire one due to affinity restrictions,
* bail out and let the idle thread to a more complete search
* outside of a critical section.
*/
if (tdq_move(steal, tdq) == NULL) {
TDQ_UNLOCK(steal);
break;
}
TDQ_UNLOCK(steal);
break;
}
spinlock_exit();
}
Restore UP build. Reviewed by: truckman Sponsored by: The FreeBSD Foundation
2018-02-23 18:26:31 +00:00
#endif
Decrease latency by not wrapping the idle loop's potentially lengthy search for a thread to steal inside a critical section. Since this allows the search to be preempted, restart the search if preemption happens since the search results found earlier may no longer be valid. Decrease the latency of starting a thread that may be assigned to this CPU during the search by polling for incoming threads during the search and switching to that thread instead of continuing the search. Test for stale search results and restart the search before going through the expense of calling tdq_lock_pair(). Retry some tests after grabbing the locks since things may have changed while waiting to get both locks. Eliminate special case handling for stealing from an SMT peer that uses 1 as the steal threshold. This can only succeed if a thread has been assigned but our SMT peer has not yet started executing it. This is quite rare and when it happens the other SMT thread is generally waiting for the same tdq lock that we hold. Basically both SMT threads are racing to grab the same spin lock. Add the kern.sched.always_steal knob from a ULE patch by jeff@. Incorporate another idea from Jeff's ULE patch. If the sched_switch() detects that the CPU is about to go idle, try to steal a thread before switching to the idle thread. Since the search for a thread to steal has to be done inside a critical section in this context, limit the impact on latency by adding the knob kern.sched.trysteal_limit to limit the topological distance of the search and don't restart the search if we detect stale results. If this search can't find an stealable thread, the idle loop can do a more complete search. Also poll for threads being assigned to this CPU during the search and switch to them instead of continuing the search. This change is responsibile for the majority of the improvement in parallel buildworld times. In sched_balance_group() change the minimum threshold from stealing a thread from 1 to 2. Poaching a newly assigned thread from a CPU that is waking up hasn't yet switched to that thread from idle is likely very rare and is likely to have the same lock race as is seen when stealing threads in the idle loop. Also use tdq_notify() to kick the destintation CPU instead of always sending an IPI. Update a stale comment, the number of transferable threads is not calculated. Reviewed by: kib (earlier version) Comments by: avg, jeff, mav MFC after: 1 month Differential Revision: https://reviews.freebsd.org/D12130
2018-02-23 00:12:51 +00:00
- Share scheduler locks between hyper-threaded cores to protect the tdq_group structure. Hyper-threaded cores won't really benefit from seperate locks anyway. - Seperate out the migration case from sched_switch to simplify the main switch code. We only migrate here if called via sched_bind(). - When preempted place the preempted thread back in the same queue at the head. - Improve the cpu group and topology infrastructure. Tested by: many on current@ Approved by: re
2007-08-03 23:38:46 +00:00
/*
* Handle migration from sched_switch(). This happens only for
* cpu binding.
*/
static struct mtx *
sched_switch_migrate(struct tdq *tdq, struct thread *td, int flags)
{
struct tdq *tdn;
Remove some, but not all, assumptions that the BSP is CPU 0 and that CPUs are numbered densely from there to n_cpus. MFC after: 1 month
2017-11-25 23:41:05 +00:00
KASSERT(!CPU_ABSENT(td_get_sched(td)->ts_cpu), ("sched_switch_migrate: "
"thread %s queued on absent CPU %d.", td->td_name,
td_get_sched(td)->ts_cpu));
Get rid of struct proc p_sched and struct thread td_sched pointers. p_sched is unused. The struct td_sched is always co-allocated with the struct thread, except for the thread0. Avoid useless indirection, instead calculate td_sched location using simple pointer arithmetic in td_get_sched(9). For thread0, which is statically allocated, create a structure to emulate layout of the dynamic allocation. Reviewed by: jhb (previous version) Sponsored by: The FreeBSD Foundation Differential revision: https://reviews.freebsd.org/D6711
2016-06-05 17:04:03 +00:00
tdn = TDQ_CPU(td_get_sched(td)->ts_cpu);
- Share scheduler locks between hyper-threaded cores to protect the tdq_group structure. Hyper-threaded cores won't really benefit from seperate locks anyway. - Seperate out the migration case from sched_switch to simplify the main switch code. We only migrate here if called via sched_bind(). - When preempted place the preempted thread back in the same queue at the head. - Improve the cpu group and topology infrastructure. Tested by: many on current@ Approved by: re
2007-08-03 23:38:46 +00:00
#ifdef SMP
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
tdq_load_rem(tdq, td);
- Share scheduler locks between hyper-threaded cores to protect the tdq_group structure. Hyper-threaded cores won't really benefit from seperate locks anyway. - Seperate out the migration case from sched_switch to simplify the main switch code. We only migrate here if called via sched_bind(). - When preempted place the preempted thread back in the same queue at the head. - Improve the cpu group and topology infrastructure. Tested by: many on current@ Approved by: re
2007-08-03 23:38:46 +00:00
/*
* Do the lock dance required to avoid LOR. We grab an extra
* spinlock nesting to prevent preemption while we're
* not holding either run-queue lock.
*/
spinlock_enter();
- Fix a race in sched_switch() of sched_4bsd. In the case of the thread being on a sleepqueue or a turnstile, the sched_lock was acquired (without the aid of the td_lock interface) and the td_lock was dropped. This was going to break locking rules on other threads willing to access to the thread (via the td_lock interface) and modify his flags (allowed as long as the container lock was different by the one used in sched_switch). In order to prevent this situation, while sched_lock is acquired there the td_lock gets blocked. [0] - Merge the ULE's internal function thread_block_switch() into the global thread_lock_block() and make the former semantic as the default for thread_lock_block(). This means that thread_lock_block() will not disable interrupts when called (and consequently thread_unlock_block() will not re-enabled them when called). This should be done manually when necessary. Note, however, that ULE's thread_unblock_switch() is not reaped because it does reflect a difference in semantic due in ULE (the td_lock may not be necessarilly still blocked_lock when calling this). While asymmetric, it does describe a remarkable difference in semantic that is good to keep in mind. [0] Reported by: Kohji Okuno <okuno dot kohji at jp dot panasonic dot com> Tested by: Giovanni Trematerra <giovanni dot trematerra at gmail dot com> MFC: 2 weeks
2010-01-23 15:54:21 +00:00
thread_lock_block(td); /* This releases the lock on tdq. */
Fix sched_switch_migrate(): - In 8.x and above the run-queue locks are nomore shared even in the HTT case, so remove the special case. - The deadlock explained in the removed comment here is still possible even with different locks, with the contribution of tdq_lock_pair(). An explanation is here: (hypotesis: a thread needs to migrate on another CPU, thread1 is doing sched_switch_migrate() and thread2 is the one handling the sched_switch() request or in other words, thread1 is the thread that needs to migrate and thread2 is a thread that is going to be preempted, most likely an idle thread. Also, 'old' is referred to the context (in terms of run-queue and CPU) thread1 is leaving and 'new' is referred to the context thread1 is going into. Finally, thread3 is doing tdq_idletd() or sched_balance() and definitively doing tdq_lock_pair()) * thread1 blocks its td_lock. Now td_lock is 'blocked' * thread1 drops its old runqueue lock * thread1 acquires the new runqueue lock * thread1 adds itself to the new runqueue and sends an IPI_PREEMPT through tdq_notify() to the new CPU * thread1 drops the new lock * thread3, scanning the runqueues, locks the old lock * thread2 received the IPI_PREEMPT and does thread_lock() with td_lock pointing to the new runqueue * thread3 wants to acquire the new runqueue lock, but it can't because it is held by thread2 so it spins * thread1 wants to acquire old lock, but as long as it is held by thread3 it can't * thread2 going further, at some point wants to switchin in thread1, but it will wait forever because thread1->td_lock is in blocked state This deadlock has been manifested mostly on 7.x and reported several time on mailing lists under the voice 'spinlock held too long'. Many thanks to des@ for having worked hard on producing suitable textdumps and Jeff for help on the comment wording. Reviewed by: jeff Reported by: des, others Tested by: des, Giovanni Trematerra <giovanni dot trematerra at gmail dot com> (STABLE_7 based version)
2009-09-15 16:56:17 +00:00
- Share scheduler locks between hyper-threaded cores to protect the tdq_group structure. Hyper-threaded cores won't really benefit from seperate locks anyway. - Seperate out the migration case from sched_switch to simplify the main switch code. We only migrate here if called via sched_bind(). - When preempted place the preempted thread back in the same queue at the head. - Improve the cpu group and topology infrastructure. Tested by: many on current@ Approved by: re
2007-08-03 23:38:46 +00:00
/*
Fix sched_switch_migrate(): - In 8.x and above the run-queue locks are nomore shared even in the HTT case, so remove the special case. - The deadlock explained in the removed comment here is still possible even with different locks, with the contribution of tdq_lock_pair(). An explanation is here: (hypotesis: a thread needs to migrate on another CPU, thread1 is doing sched_switch_migrate() and thread2 is the one handling the sched_switch() request or in other words, thread1 is the thread that needs to migrate and thread2 is a thread that is going to be preempted, most likely an idle thread. Also, 'old' is referred to the context (in terms of run-queue and CPU) thread1 is leaving and 'new' is referred to the context thread1 is going into. Finally, thread3 is doing tdq_idletd() or sched_balance() and definitively doing tdq_lock_pair()) * thread1 blocks its td_lock. Now td_lock is 'blocked' * thread1 drops its old runqueue lock * thread1 acquires the new runqueue lock * thread1 adds itself to the new runqueue and sends an IPI_PREEMPT through tdq_notify() to the new CPU * thread1 drops the new lock * thread3, scanning the runqueues, locks the old lock * thread2 received the IPI_PREEMPT and does thread_lock() with td_lock pointing to the new runqueue * thread3 wants to acquire the new runqueue lock, but it can't because it is held by thread2 so it spins * thread1 wants to acquire old lock, but as long as it is held by thread3 it can't * thread2 going further, at some point wants to switchin in thread1, but it will wait forever because thread1->td_lock is in blocked state This deadlock has been manifested mostly on 7.x and reported several time on mailing lists under the voice 'spinlock held too long'. Many thanks to des@ for having worked hard on producing suitable textdumps and Jeff for help on the comment wording. Reviewed by: jeff Reported by: des, others Tested by: des, Giovanni Trematerra <giovanni dot trematerra at gmail dot com> (STABLE_7 based version)
2009-09-15 16:56:17 +00:00
* Acquire both run-queue locks before placing the thread on the new
* run-queue to avoid deadlocks created by placing a thread with a
* blocked lock on the run-queue of a remote processor. The deadlock
* occurs when a third processor attempts to lock the two queues in
* question while the target processor is spinning with its own
* run-queue lock held while waiting for the blocked lock to clear.
- Share scheduler locks between hyper-threaded cores to protect the tdq_group structure. Hyper-threaded cores won't really benefit from seperate locks anyway. - Seperate out the migration case from sched_switch to simplify the main switch code. We only migrate here if called via sched_bind(). - When preempted place the preempted thread back in the same queue at the head. - Improve the cpu group and topology infrastructure. Tested by: many on current@ Approved by: re
2007-08-03 23:38:46 +00:00
*/
Fix sched_switch_migrate(): - In 8.x and above the run-queue locks are nomore shared even in the HTT case, so remove the special case. - The deadlock explained in the removed comment here is still possible even with different locks, with the contribution of tdq_lock_pair(). An explanation is here: (hypotesis: a thread needs to migrate on another CPU, thread1 is doing sched_switch_migrate() and thread2 is the one handling the sched_switch() request or in other words, thread1 is the thread that needs to migrate and thread2 is a thread that is going to be preempted, most likely an idle thread. Also, 'old' is referred to the context (in terms of run-queue and CPU) thread1 is leaving and 'new' is referred to the context thread1 is going into. Finally, thread3 is doing tdq_idletd() or sched_balance() and definitively doing tdq_lock_pair()) * thread1 blocks its td_lock. Now td_lock is 'blocked' * thread1 drops its old runqueue lock * thread1 acquires the new runqueue lock * thread1 adds itself to the new runqueue and sends an IPI_PREEMPT through tdq_notify() to the new CPU * thread1 drops the new lock * thread3, scanning the runqueues, locks the old lock * thread2 received the IPI_PREEMPT and does thread_lock() with td_lock pointing to the new runqueue * thread3 wants to acquire the new runqueue lock, but it can't because it is held by thread2 so it spins * thread1 wants to acquire old lock, but as long as it is held by thread3 it can't * thread2 going further, at some point wants to switchin in thread1, but it will wait forever because thread1->td_lock is in blocked state This deadlock has been manifested mostly on 7.x and reported several time on mailing lists under the voice 'spinlock held too long'. Many thanks to des@ for having worked hard on producing suitable textdumps and Jeff for help on the comment wording. Reviewed by: jeff Reported by: des, others Tested by: des, Giovanni Trematerra <giovanni dot trematerra at gmail dot com> (STABLE_7 based version)
2009-09-15 16:56:17 +00:00
tdq_lock_pair(tdn, tdq);
tdq_add(tdn, td, flags);
Revert r313814 and r313816 Something evidently got mangled in my git tree in between testing and review, as an old and broken version of the patch was apparently submitted to svn. Revert this while I work out what went wrong. Reported by: tuexen Pointy hat to: rstone
2017-02-16 21:18:31 +00:00
tdq_notify(tdn, td);
Fix sched_switch_migrate(): - In 8.x and above the run-queue locks are nomore shared even in the HTT case, so remove the special case. - The deadlock explained in the removed comment here is still possible even with different locks, with the contribution of tdq_lock_pair(). An explanation is here: (hypotesis: a thread needs to migrate on another CPU, thread1 is doing sched_switch_migrate() and thread2 is the one handling the sched_switch() request or in other words, thread1 is the thread that needs to migrate and thread2 is a thread that is going to be preempted, most likely an idle thread. Also, 'old' is referred to the context (in terms of run-queue and CPU) thread1 is leaving and 'new' is referred to the context thread1 is going into. Finally, thread3 is doing tdq_idletd() or sched_balance() and definitively doing tdq_lock_pair()) * thread1 blocks its td_lock. Now td_lock is 'blocked' * thread1 drops its old runqueue lock * thread1 acquires the new runqueue lock * thread1 adds itself to the new runqueue and sends an IPI_PREEMPT through tdq_notify() to the new CPU * thread1 drops the new lock * thread3, scanning the runqueues, locks the old lock * thread2 received the IPI_PREEMPT and does thread_lock() with td_lock pointing to the new runqueue * thread3 wants to acquire the new runqueue lock, but it can't because it is held by thread2 so it spins * thread1 wants to acquire old lock, but as long as it is held by thread3 it can't * thread2 going further, at some point wants to switchin in thread1, but it will wait forever because thread1->td_lock is in blocked state This deadlock has been manifested mostly on 7.x and reported several time on mailing lists under the voice 'spinlock held too long'. Many thanks to des@ for having worked hard on producing suitable textdumps and Jeff for help on the comment wording. Reviewed by: jeff Reported by: des, others Tested by: des, Giovanni Trematerra <giovanni dot trematerra at gmail dot com> (STABLE_7 based version)
2009-09-15 16:56:17 +00:00
TDQ_UNLOCK(tdn);
- Share scheduler locks between hyper-threaded cores to protect the tdq_group structure. Hyper-threaded cores won't really benefit from seperate locks anyway. - Seperate out the migration case from sched_switch to simplify the main switch code. We only migrate here if called via sched_bind(). - When preempted place the preempted thread back in the same queue at the head. - Improve the cpu group and topology infrastructure. Tested by: many on current@ Approved by: re
2007-08-03 23:38:46 +00:00
spinlock_exit();
#endif
return (TDQ_LOCKPTR(tdn));
}
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
- Fix a race in sched_switch() of sched_4bsd. In the case of the thread being on a sleepqueue or a turnstile, the sched_lock was acquired (without the aid of the td_lock interface) and the td_lock was dropped. This was going to break locking rules on other threads willing to access to the thread (via the td_lock interface) and modify his flags (allowed as long as the container lock was different by the one used in sched_switch). In order to prevent this situation, while sched_lock is acquired there the td_lock gets blocked. [0] - Merge the ULE's internal function thread_block_switch() into the global thread_lock_block() and make the former semantic as the default for thread_lock_block(). This means that thread_lock_block() will not disable interrupts when called (and consequently thread_unlock_block() will not re-enabled them when called). This should be done manually when necessary. Note, however, that ULE's thread_unblock_switch() is not reaped because it does reflect a difference in semantic due in ULE (the td_lock may not be necessarilly still blocked_lock when calling this). While asymmetric, it does describe a remarkable difference in semantic that is good to keep in mind. [0] Reported by: Kohji Okuno <okuno dot kohji at jp dot panasonic dot com> Tested by: Giovanni Trematerra <giovanni dot trematerra at gmail dot com> MFC: 2 weeks
2010-01-23 15:54:21 +00:00
* Variadic version of thread_lock_unblock() that does not assume td_lock
* is blocked.
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
*/
static inline void
thread_unblock_switch(struct thread *td, struct mtx *mtx)
{
atomic_store_rel_ptr((volatile uintptr_t *)&td->td_lock,
(uintptr_t)mtx);
}
/*
* Switch threads. This function has to handle threads coming in while
* blocked for some reason, running, or idle. It also must deal with
* migrating a thread from one queue to another as running threads may
* be assigned elsewhere via binding.
*/
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
void
Add some code to allow threads to nominat a sibling to run if theyu are going to sleep. MFC after: 1 week
2004-09-10 21:04:38 +00:00
sched_switch(struct thread *td, struct thread *newtd, int flags)
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
{
- More search and replace prettying.
2006-12-29 12:55:32 +00:00
struct tdq *tdq;
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
struct td_sched *ts;
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
struct mtx *mtx;
- Share scheduler locks between hyper-threaded cores to protect the tdq_group structure. Hyper-threaded cores won't really benefit from seperate locks anyway. - Seperate out the migration case from sched_switch to simplify the main switch code. We only migrate here if called via sched_bind(). - When preempted place the preempted thread back in the same queue at the head. - Improve the cpu group and topology infrastructure. Tested by: many on current@ Approved by: re
2007-08-03 23:38:46 +00:00
int srqflag;
Rework r220198 change (by fabient). I believe it solves the problem from the wrong direction. Before it, if preemption and end of time slice happen same time, thread was put to the head of the queue as for only preemption. It could cause single thread to run for indefinitely long time. r220198 handles it by not clearing TDF_NEEDRESCHED in case of preemption. But that causes delayed context switch every time preemption happens, even when not needed. Solve problem by introducing scheduler-specifoc thread flag TDF_SLICEEND, set when thread's time slice is over and it should be put to the tail of queue. Using SW_PREEMPT flag for that purpose as it was before just not enough informative to work correctly. On my tests this by 2-3 times reduces run time deviation (improves fairness) in cases when several threads share one CPU. Reviewed by: fabient MFC after: 2 months Sponsored by: iXsystems, Inc.
2012-08-09 19:26:13 +00:00
int cpuid, preempted;
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
Commit 1/14 of sched_lock decomposition. - Move all scheduler locking into the schedulers utilizing a technique similar to solaris's container locking. - A per-process spinlock is now used to protect the queue of threads, thread count, suspension count, p_sflags, and other process related scheduling fields. - The new thread lock is actually a pointer to a spinlock for the container that the thread is currently owned by. The container may be a turnstile, sleepqueue, or run queue. - thread_lock() is now used to protect access to thread related scheduling fields. thread_unlock() unlocks the lock and thread_set_lock() implements the transition from one lock to another. - A new "blocked_lock" is used in cases where it is not safe to hold the actual thread's lock yet we must prevent access to the thread. - sched_throw() and sched_fork_exit() are introduced to allow the schedulers to fix-up locking at these points. - Add some minor infrastructure for optionally exporting scheduler statistics that were invaluable in solving performance problems with this patch. Generally these statistics allow you to differentiate between different causes of context switches. Tested by: kris, current@ Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc. Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:50:30 +00:00
THREAD_LOCK_ASSERT(td, MA_OWNED);
- Remove some dead code and comments related to KSE. - Don't set tdq_lowpri on every switch, it should be precisely maintained now. - Add some comments to sched_thread_priority().
2008-03-19 07:36:37 +00:00
KASSERT(newtd == NULL, ("sched_switch: Unsupported newtd argument"));
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
cpuid = PCPU_GET(cpuid);
tdq = TDQ_CPU(cpuid);
Get rid of struct proc p_sched and struct thread td_sched pointers. p_sched is unused. The struct td_sched is always co-allocated with the struct thread, except for the thread0. Avoid useless indirection, instead calculate td_sched location using simple pointer arithmetic in td_get_sched(9). For thread0, which is statically allocated, create a structure to emulate layout of the dynamic allocation. Reviewed by: jhb (previous version) Sponsored by: The FreeBSD Foundation Differential revision: https://reviews.freebsd.org/D6711
2016-06-05 17:04:03 +00:00
ts = td_get_sched(td);
- Share scheduler locks between hyper-threaded cores to protect the tdq_group structure. Hyper-threaded cores won't really benefit from seperate locks anyway. - Seperate out the migration case from sched_switch to simplify the main switch code. We only migrate here if called via sched_bind(). - When preempted place the preempted thread back in the same queue at the head. - Improve the cpu group and topology infrastructure. Tested by: many on current@ Approved by: re
2007-08-03 23:38:46 +00:00
mtx = td->td_lock;
Rewrite thread CPU usage percentage math to not depend on periodic calls with HZ rate through the sched_tick() calls from hardclock(). Potentially it can be used to improve precision, but now it is just minus one more reason to call hardclock() for every HZ tick on every active CPU. SCHED_4BSD never used sched_tick(), but keep it in place for now, as at least SCHED_FBFS existing in patches out of the tree depends on it. MFC after: 1 month
2012-03-13 08:18:54 +00:00
sched_pctcpu_update(ts, 1);
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
ts->ts_rltick = ticks;
- Introduce a new flag KEF_HOLD that prevents sched_add() from doing a migration. Use this in sched_prio() and sched_switch() to stop us from migrating threads that are in short term sleeps or are runnable. These extra migrations were added in the patches to support KSE. - Only set NEEDRESCHED if the thread we're adding in sched_add() is a lower priority and is being placed on the current queue. - Fix some minor whitespace problems.
2004-08-12 07:56:33 +00:00
td->td_lastcpu = td->td_oncpu;
Move the _oncpu entry from the KSE to the thread. The entry in the KSE still exists but it's purpose will change a bit when we add the ability to lock a KSE to a cpu.
2003-04-10 17:35:44 +00:00
td->td_oncpu = NOCPU;
fix a thread preemption regression in schedulers introduced in r270423 Commit r270423 fixed a regression in sched_yield() that was introduced in earlier changes. Unfortunately, at the same time it introduced an new regression. The problem is that SWT_RELINQUISH (6), like all other SWT_* constants and unlike SW_* flags, is not a bit flag. So, (flags & SWT_RELINQUISH) is true in cases where that was not really indended, for example, with SWT_OWEPREEMPT (2) and SWT_REMOTEPREEMPT (11). A straight forward fix would be to use (flags & SW_TYPE_MASK) == SWT_RELINQUISH, but my impression is that the switch types are designed mostly for gathering statistics, not for influencing scheduling decisions. So, I decided that it would be better to check for SW_PREEMPT flag instead. That's also the same flag that was checked before r239157. I double-checked how that flag is used and I am confident that the flag is set only in the places where we really have the preemption: - critical_exit + td_owepreempt - sched_preempt in the ULE scheduler - sched_preempt in the 4BSD scheduler Reviewed by: kib, mav MFC after: 4 days Sponsored by: Panzura Differential Revision: https://reviews.freebsd.org/D9230
2017-01-19 18:46:41 +00:00
preempted = (td->td_flags & TDF_SLICEEND) == 0 &&
(flags & SW_PREEMPT) != 0;
Rework r220198 change (by fabient). I believe it solves the problem from the wrong direction. Before it, if preemption and end of time slice happen same time, thread was put to the head of the queue as for only preemption. It could cause single thread to run for indefinitely long time. r220198 handles it by not clearing TDF_NEEDRESCHED in case of preemption. But that causes delayed context switch every time preemption happens, even when not needed. Solve problem by introducing scheduler-specifoc thread flag TDF_SLICEEND, set when thread's time slice is over and it should be put to the tail of queue. Using SW_PREEMPT flag for that purpose as it was before just not enough informative to work correctly. On my tests this by 2-3 times reduces run time deviation (improves fairness) in cases when several threads share one CPU. Reviewed by: fabient MFC after: 2 months Sponsored by: iXsystems, Inc.
2012-08-09 19:26:13 +00:00
td->td_flags &= ~(TDF_NEEDRESCHED | TDF_SLICEEND);
Sprinkle some volatile magic and rearrange things a bit to avoid race conditions in critical_exit now that it no longer blocks interrupts. Reviewed by: jhb
2005-04-08 03:37:53 +00:00
td->td_owepreempt = 0;
Several optimizations to sched_idletd(): - Do not try to steal load from other CPUs if there was no contest switches on this CPU (i.e. it was idle all the time and woke up just for bus mastering or TLB shutdown). If current CPU was idle, then it is quite unlikely that some other CPU has load to steal. Under high I/O rate, when TLB shutdowns cause numerous CPU wakeups, on 24-CPU system load stealing code may consume up to 25% of all CPU time without giving any benefits. - Change code that implements spinning for load to restart spin in case of context switch. Previous code periodically called cpu_idle() even under high interrupt/context switch rate. - Rise spinning threshold to 10KHz, where it gives at least some effect that may worth consumed power. Reviewed by: jeff@
2012-11-10 07:02:57 +00:00
if (!TD_IS_IDLETHREAD(td))
tdq->tdq_switchcnt++;
- In sched_switch(), if a thread has been assigned, don't touch the runqueues or load. These things have already been taken care of in sched_bind() which should be the only place that we're switching in an assigned thread.
2003-12-11 04:00:49 +00:00
/*
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
* The lock pointer in an idle thread should never change. Reset it
* to CAN_RUN as well.
Commit 1/14 of sched_lock decomposition. - Move all scheduler locking into the schedulers utilizing a technique similar to solaris's container locking. - A per-process spinlock is now used to protect the queue of threads, thread count, suspension count, p_sflags, and other process related scheduling fields. - The new thread lock is actually a pointer to a spinlock for the container that the thread is currently owned by. The container may be a turnstile, sleepqueue, or run queue. - thread_lock() is now used to protect access to thread related scheduling fields. thread_unlock() unlocks the lock and thread_set_lock() implements the transition from one lock to another. - A new "blocked_lock" is used in cases where it is not safe to hold the actual thread's lock yet we must prevent access to the thread. - sched_throw() and sched_fork_exit() are introduced to allow the schedulers to fix-up locking at these points. - Add some minor infrastructure for optionally exporting scheduler statistics that were invaluable in solving performance problems with this patch. Generally these statistics allow you to differentiate between different causes of context switches. Tested by: kris, current@ Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc. Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:50:30 +00:00
*/
Instead of doing comparisons using the pcpu area to see if a thread is an idle thread, just see if it has the IDLETD flag set. That flag will probably move to the pflags word as it's permenent and never chenges for the life of the system so it doesn't need locking.
2007-03-08 06:44:34 +00:00
if (TD_IS_IDLETHREAD(td)) {
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
- Fix a long standing problem where an ithread would not honor sched_pin(). - Remove the sched_add wrapper that used sched_add_internal() as a backend. Its only purpose was to interpret one flag and turn it into an int. Do the right thing and interpret the flag in sched_add() instead. - Pass the flag argument to sched_add() to kseq_runq_add() so that we can get the SRQ_PREEMPT optimization too. - Add a KEF_INTERNAL flag. If KEF_INTERNAL is set we don't adjust the SLOT counts, otherwise the slot counts are adjusted as soon as we enter sched_add() or sched_rem() rather than when the thread is actually placed on the run queue. This greatly simplifies the handling of slots. - Remove the explicit prevention of migration for ithreads on non-x86 platforms. This was never shown to have any real benefit. - Remove the unused class argument to KSE_CAN_MIGRATE(). - Add ktr points for thread migration events. - Fix a long standing bug on platforms which don't initialize the cpu topology. The ksg_maxid variable was never correctly set on these platforms which caused the long term load balancer to never inspect more than the first group or processor. - Fix another bug which prevented the long term load balancer from working properly. If stathz != hz we can't expect sched_clock() to be called on the exact tick count that we're anticipating. - Rearrange sched_switch() a bit to reduce indentation levels.
2004-12-26 22:56:08 +00:00
TD_SET_CAN_RUN(td);
Commit 1/14 of sched_lock decomposition. - Move all scheduler locking into the schedulers utilizing a technique similar to solaris's container locking. - A per-process spinlock is now used to protect the queue of threads, thread count, suspension count, p_sflags, and other process related scheduling fields. - The new thread lock is actually a pointer to a spinlock for the container that the thread is currently owned by. The container may be a turnstile, sleepqueue, or run queue. - thread_lock() is now used to protect access to thread related scheduling fields. thread_unlock() unlocks the lock and thread_set_lock() implements the transition from one lock to another. - A new "blocked_lock" is used in cases where it is not safe to hold the actual thread's lock yet we must prevent access to the thread. - sched_throw() and sched_fork_exit() are introduced to allow the schedulers to fix-up locking at these points. - Add some minor infrastructure for optionally exporting scheduler statistics that were invaluable in solving performance problems with this patch. Generally these statistics allow you to differentiate between different causes of context switches. Tested by: kris, current@ Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc. Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:50:30 +00:00
} else if (TD_IS_RUNNING(td)) {
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
Rework r220198 change (by fabient). I believe it solves the problem from the wrong direction. Before it, if preemption and end of time slice happen same time, thread was put to the head of the queue as for only preemption. It could cause single thread to run for indefinitely long time. r220198 handles it by not clearing TDF_NEEDRESCHED in case of preemption. But that causes delayed context switch every time preemption happens, even when not needed. Solve problem by introducing scheduler-specifoc thread flag TDF_SLICEEND, set when thread's time slice is over and it should be put to the tail of queue. Using SW_PREEMPT flag for that purpose as it was before just not enough informative to work correctly. On my tests this by 2-3 times reduces run time deviation (improves fairness) in cases when several threads share one CPU. Reviewed by: fabient MFC after: 2 months Sponsored by: iXsystems, Inc.
2012-08-09 19:26:13 +00:00
srqflag = preempted ?
Commit 1/14 of sched_lock decomposition. - Move all scheduler locking into the schedulers utilizing a technique similar to solaris's container locking. - A per-process spinlock is now used to protect the queue of threads, thread count, suspension count, p_sflags, and other process related scheduling fields. - The new thread lock is actually a pointer to a spinlock for the container that the thread is currently owned by. The container may be a turnstile, sleepqueue, or run queue. - thread_lock() is now used to protect access to thread related scheduling fields. thread_unlock() unlocks the lock and thread_set_lock() implements the transition from one lock to another. - A new "blocked_lock" is used in cases where it is not safe to hold the actual thread's lock yet we must prevent access to the thread. - sched_throw() and sched_fork_exit() are introduced to allow the schedulers to fix-up locking at these points. - Add some minor infrastructure for optionally exporting scheduler statistics that were invaluable in solving performance problems with this patch. Generally these statistics allow you to differentiate between different causes of context switches. Tested by: kris, current@ Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc. Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:50:30 +00:00
SRQ_OURSELF|SRQ_YIELDING|SRQ_PREEMPTED :
- Share scheduler locks between hyper-threaded cores to protect the tdq_group structure. Hyper-threaded cores won't really benefit from seperate locks anyway. - Seperate out the migration case from sched_switch to simplify the main switch code. We only migrate here if called via sched_bind(). - When preempted place the preempted thread back in the same queue at the head. - Improve the cpu group and topology infrastructure. Tested by: many on current@ Approved by: re
2007-08-03 23:38:46 +00:00
SRQ_OURSELF|SRQ_YIELDING;
Fix UP build. MFC after: 2 weeks
2010-09-02 16:23:05 +00:00
#ifdef SMP
Fix a bug with sched_affinity() where it checks td_pinned of another thread in a racy manner, which can lead to attempting to migrate a thread that is pinned to a CPU. Instead, have sched_switch() determine which CPU a thread should run on if the current one is not allowed. KASSERT in sched_bind() that the thread is not yet pinned to a CPU. KASSERT in sched_switch() that only migratable threads or those moving due to a sched_bind() are changing CPUs. sched_affinity code came from jhb@. MFC after: 2 weeks
2010-09-01 20:32:47 +00:00
if (THREAD_CAN_MIGRATE(td) && !THREAD_CAN_SCHED(td, ts->ts_cpu))
ts->ts_cpu = sched_pickcpu(td, 0);
Fix UP build. MFC after: 2 weeks
2010-09-02 16:23:05 +00:00
#endif
- Share scheduler locks between hyper-threaded cores to protect the tdq_group structure. Hyper-threaded cores won't really benefit from seperate locks anyway. - Seperate out the migration case from sched_switch to simplify the main switch code. We only migrate here if called via sched_bind(). - When preempted place the preempted thread back in the same queue at the head. - Improve the cpu group and topology infrastructure. Tested by: many on current@ Approved by: re
2007-08-03 23:38:46 +00:00
if (ts->ts_cpu == cpuid)
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
tdq_runq_add(tdq, td, srqflag);
Fix a bug with sched_affinity() where it checks td_pinned of another thread in a racy manner, which can lead to attempting to migrate a thread that is pinned to a CPU. Instead, have sched_switch() determine which CPU a thread should run on if the current one is not allowed. KASSERT in sched_bind() that the thread is not yet pinned to a CPU. KASSERT in sched_switch() that only migratable threads or those moving due to a sched_bind() are changing CPUs. sched_affinity code came from jhb@. MFC after: 2 weeks
2010-09-01 20:32:47 +00:00
else {
KASSERT(THREAD_CAN_MIGRATE(td) ||
(ts->ts_flags & TSF_BOUND) != 0,
("Thread %p shouldn't migrate", td));
- Share scheduler locks between hyper-threaded cores to protect the tdq_group structure. Hyper-threaded cores won't really benefit from seperate locks anyway. - Seperate out the migration case from sched_switch to simplify the main switch code. We only migrate here if called via sched_bind(). - When preempted place the preempted thread back in the same queue at the head. - Improve the cpu group and topology infrastructure. Tested by: many on current@ Approved by: re
2007-08-03 23:38:46 +00:00
mtx = sched_switch_migrate(tdq, td, srqflag);
Fix a bug with sched_affinity() where it checks td_pinned of another thread in a racy manner, which can lead to attempting to migrate a thread that is pinned to a CPU. Instead, have sched_switch() determine which CPU a thread should run on if the current one is not allowed. KASSERT in sched_bind() that the thread is not yet pinned to a CPU. KASSERT in sched_switch() that only migratable threads or those moving due to a sched_bind() are changing CPUs. sched_affinity code came from jhb@. MFC after: 2 weeks
2010-09-01 20:32:47 +00:00
}
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
} else {
/* This thread must be going to sleep. */
TDQ_LOCK(tdq);
- Fix a race in sched_switch() of sched_4bsd. In the case of the thread being on a sleepqueue or a turnstile, the sched_lock was acquired (without the aid of the td_lock interface) and the td_lock was dropped. This was going to break locking rules on other threads willing to access to the thread (via the td_lock interface) and modify his flags (allowed as long as the container lock was different by the one used in sched_switch). In order to prevent this situation, while sched_lock is acquired there the td_lock gets blocked. [0] - Merge the ULE's internal function thread_block_switch() into the global thread_lock_block() and make the former semantic as the default for thread_lock_block(). This means that thread_lock_block() will not disable interrupts when called (and consequently thread_unlock_block() will not re-enabled them when called). This should be done manually when necessary. Note, however, that ULE's thread_unblock_switch() is not reaped because it does reflect a difference in semantic due in ULE (the td_lock may not be necessarilly still blocked_lock when calling this). While asymmetric, it does describe a remarkable difference in semantic that is good to keep in mind. [0] Reported by: Kohji Okuno <okuno dot kohji at jp dot panasonic dot com> Tested by: Giovanni Trematerra <giovanni dot trematerra at gmail dot com> MFC: 2 weeks
2010-01-23 15:54:21 +00:00
mtx = thread_lock_block(td);
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
tdq_load_rem(tdq, td);
Restore UP build. Reviewed by: truckman Sponsored by: The FreeBSD Foundation
2018-02-23 18:26:31 +00:00
#ifdef SMP
Decrease latency by not wrapping the idle loop's potentially lengthy search for a thread to steal inside a critical section. Since this allows the search to be preempted, restart the search if preemption happens since the search results found earlier may no longer be valid. Decrease the latency of starting a thread that may be assigned to this CPU during the search by polling for incoming threads during the search and switching to that thread instead of continuing the search. Test for stale search results and restart the search before going through the expense of calling tdq_lock_pair(). Retry some tests after grabbing the locks since things may have changed while waiting to get both locks. Eliminate special case handling for stealing from an SMT peer that uses 1 as the steal threshold. This can only succeed if a thread has been assigned but our SMT peer has not yet started executing it. This is quite rare and when it happens the other SMT thread is generally waiting for the same tdq lock that we hold. Basically both SMT threads are racing to grab the same spin lock. Add the kern.sched.always_steal knob from a ULE patch by jeff@. Incorporate another idea from Jeff's ULE patch. If the sched_switch() detects that the CPU is about to go idle, try to steal a thread before switching to the idle thread. Since the search for a thread to steal has to be done inside a critical section in this context, limit the impact on latency by adding the knob kern.sched.trysteal_limit to limit the topological distance of the search and don't restart the search if we detect stale results. If this search can't find an stealable thread, the idle loop can do a more complete search. Also poll for threads being assigned to this CPU during the search and switch to them instead of continuing the search. This change is responsibile for the majority of the improvement in parallel buildworld times. In sched_balance_group() change the minimum threshold from stealing a thread from 1 to 2. Poaching a newly assigned thread from a CPU that is waking up hasn't yet switched to that thread from idle is likely very rare and is likely to have the same lock race as is seen when stealing threads in the idle loop. Also use tdq_notify() to kick the destintation CPU instead of always sending an IPI. Update a stale comment, the number of transferable threads is not calculated. Reviewed by: kib (earlier version) Comments by: avg, jeff, mav MFC after: 1 month Differential Revision: https://reviews.freebsd.org/D12130
2018-02-23 00:12:51 +00:00
if (tdq->tdq_load == 0)
tdq_trysteal(tdq);
Restore UP build. Reviewed by: truckman Sponsored by: The FreeBSD Foundation
2018-02-23 18:26:31 +00:00
#endif
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
}
move thread switch tracing from mi_switch to sched_switch This is done so that the thread state changes during the switch are not confused with the thread state changes reported when the thread spins on a lock. Here is an example, three consecutive entries for the same thread (from top to bottom): KTRGRAPH group:"thread", id:"zio_write_intr_3 tid 100260", state:"sleep", attributes: prio:84, wmesg:"-", lockname:"(null)" KTRGRAPH group:"thread", id:"zio_write_intr_3 tid 100260", state:"spinning", attributes: lockname:"sched lock 1" KTRGRAPH group:"thread", id:"zio_write_intr_3 tid 100260", state:"running", attributes: none The above trace could leave an impression that the final state of the thread was "running". After this change the sleep state will be reported after the "spinning" and "running" states reported for the sched lock. Reviewed by: jhb, markj MFC after: 1 week Sponsored by: Panzura Differential Revision: https://reviews.freebsd.org/D9961
2017-03-23 08:57:04 +00:00
#if (KTR_COMPILE & KTR_SCHED) != 0
if (TD_IS_IDLETHREAD(td))
KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "idle",
"prio:%d", td->td_priority);
else
KTR_STATE3(KTR_SCHED, "thread", sched_tdname(td), KTDSTATE(td),
"prio:%d", td->td_priority, "wmesg:\"%s\"", td->td_wmesg,
"lockname:\"%s\"", td->td_lockname);
#endif
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* We enter here with the thread blocked and assigned to the
* appropriate cpu run-queue or sleep-queue and with the current
* thread-queue locked.
*/
TDQ_LOCK_ASSERT(tdq, MA_OWNED | MA_NOTRECURSED);
newtd = choosethread();
/*
* Call the MD code to switch contexts if necessary.
*/
Bring a working snapshot of hwpmc(4), its associated libraries, userland utilities and documentation into -CURRENT. Bump FreeBSD_version. Reviewed by: alc, jhb (kernel changes)
2005-04-19 04:01:25 +00:00
if (td != newtd) {
#ifdef HWPMC_HOOKS
if (PMC_PROC_IS_USING_PMCS(td->td_proc))
PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT);
#endif
dtrace sdt: remove the ugly sname parameter of SDT_PROBE_DEFINE In its stead use the Solaris / illumos approach of emulating '-' (dash) in probe names with '__' (two consecutive underscores). Reviewed by: markj MFC after: 3 weeks
2013-11-26 08:46:27 +00:00
SDT_PROBE2(sched, , , off__cpu, newtd, newtd->td_proc);
- Re-implement lock profiling in such a way that it no longer breaks the ABI when enabled. There is no longer an embedded lock_profile_object in each lock. Instead a list of lock_profile_objects is kept per-thread for each lock it may own. The cnt_hold statistic is now always 0 to facilitate this. - Support shared locking by tracking individual lock instances and statistics in the per-thread per-instance lock_profile_object. - Make the lock profiling hash table a per-cpu singly linked list with a per-cpu static lock_prof allocator. This removes the need for an array of spinlocks and reduces cache contention between cores. - Use a seperate hash for spinlocks and other locks so that only a critical_enter() is required and not a spinlock_enter() to modify the per-cpu tables. - Count time spent spinning in the lock statistics. - Remove the LOCK_PROFILE_SHARED option as it is always supported now. - Specifically drop and release the scheduler locks in both schedulers since we track owners now. In collaboration with: Kip Macy Sponsored by: Nokia
2007-12-15 23:13:31 +00:00
lock_profile_release_lock(&TDQ_LOCKPTR(tdq)->lock_object);
- Reassign the thread queue lock to newtd prior to switching. Assigning after the switch leads to a race where the outgoing thread still owns the local queue lock while another cpu may switch it in. This race is only possible on machines where cpu_switch can take significantly longer on different cpus which in practice means HTT machines with unfair thread scheduling algorithms. Found by: kris (of course) Approved by: re
2007-10-02 01:30:18 +00:00
TDQ_LOCKPTR(tdq)->mtx_lock = (uintptr_t)newtd;
Get rid of struct proc p_sched and struct thread td_sched pointers. p_sched is unused. The struct td_sched is always co-allocated with the struct thread, except for the thread0. Avoid useless indirection, instead calculate td_sched location using simple pointer arithmetic in td_get_sched(9). For thread0, which is statically allocated, create a structure to emulate layout of the dynamic allocation. Reviewed by: jhb (previous version) Sponsored by: The FreeBSD Foundation Differential revision: https://reviews.freebsd.org/D6711
2016-06-05 17:04:03 +00:00
sched_pctcpu_update(td_get_sched(newtd), 0);
Add the vtime (virtual time) hooks for DTrace.
2008-05-25 01:44:58 +00:00
#ifdef KDTRACE_HOOKS
/*
* If DTrace has set the active vtime enum to anything
* other than INACTIVE (0), then it should have set the
* function to call.
*/
if (dtrace_vtime_active)
(*dtrace_vtime_switch_func)(newtd);
#endif
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
cpu_switch(td, newtd, mtx);
/*
* We may return from cpu_switch on a different cpu. However,
* we always return with td_lock pointing to the current cpu's
* run queue lock.
*/
cpuid = PCPU_GET(cpuid);
tdq = TDQ_CPU(cpuid);
- Re-implement lock profiling in such a way that it no longer breaks the ABI when enabled. There is no longer an embedded lock_profile_object in each lock. Instead a list of lock_profile_objects is kept per-thread for each lock it may own. The cnt_hold statistic is now always 0 to facilitate this. - Support shared locking by tracking individual lock instances and statistics in the per-thread per-instance lock_profile_object. - Make the lock profiling hash table a per-cpu singly linked list with a per-cpu static lock_prof allocator. This removes the need for an array of spinlocks and reduces cache contention between cores. - Use a seperate hash for spinlocks and other locks so that only a critical_enter() is required and not a spinlock_enter() to modify the per-cpu tables. - Count time spent spinning in the lock statistics. - Remove the LOCK_PROFILE_SHARED option as it is always supported now. - Specifically drop and release the scheduler locks in both schedulers since we track owners now. In collaboration with: Kip Macy Sponsored by: Nokia
2007-12-15 23:13:31 +00:00
lock_profile_obtain_lock_success(
&TDQ_LOCKPTR(tdq)->lock_object, 0, 0, __FILE__, __LINE__);
Implement the DTrace sched provider. This implementation aims to be compatible with the sched provider implemented by Solaris and its open- source derivatives. Full documentation of the sched provider can be found on Oracle's DTrace wiki pages. Note that for compatibility with scripts originally written for Solaris, serveral probes are defined that will never fire. These probes are defined to fire when Solaris-specific features perform certain actions. As these features are not present in FreeBSD, the probes can never fire. Also, I have added a two probes that are not defined in Solaris, lend-pri and load-change. These probes have been added to make it possible to collect schedgraph data with DTrace. Finally, a few probes are defined in Solaris to take a cpuinfo_t * argument. As it was not immediately clear to me how to translate that to FreeBSD, currently those probes are passed NULL in place of a cpuinfo_t *. Sponsored by: Sandvine Incorporated MFC after: 2 weeks
2012-05-15 01:30:25 +00:00
dtrace sdt: remove the ugly sname parameter of SDT_PROBE_DEFINE In its stead use the Solaris / illumos approach of emulating '-' (dash) in probe names with '__' (two consecutive underscores). Reviewed by: markj MFC after: 3 weeks
2013-11-26 08:46:27 +00:00
SDT_PROBE0(sched, , , on__cpu);
Bring a working snapshot of hwpmc(4), its associated libraries, userland utilities and documentation into -CURRENT. Bump FreeBSD_version. Reviewed by: alc, jhb (kernel changes)
2005-04-19 04:01:25 +00:00
#ifdef HWPMC_HOOKS
if (PMC_PROC_IS_USING_PMCS(td->td_proc))
PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_IN);
#endif
Implement the DTrace sched provider. This implementation aims to be compatible with the sched provider implemented by Solaris and its open- source derivatives. Full documentation of the sched provider can be found on Oracle's DTrace wiki pages. Note that for compatibility with scripts originally written for Solaris, serveral probes are defined that will never fire. These probes are defined to fire when Solaris-specific features perform certain actions. As these features are not present in FreeBSD, the probes can never fire. Also, I have added a two probes that are not defined in Solaris, lend-pri and load-change. These probes have been added to make it possible to collect schedgraph data with DTrace. Finally, a few probes are defined in Solaris to take a cpuinfo_t * argument. As it was not immediately clear to me how to translate that to FreeBSD, currently those probes are passed NULL in place of a cpuinfo_t *. Sponsored by: Sandvine Incorporated MFC after: 2 weeks
2012-05-15 01:30:25 +00:00
} else {
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
thread_unblock_switch(td, mtx);
dtrace sdt: remove the ugly sname parameter of SDT_PROBE_DEFINE In its stead use the Solaris / illumos approach of emulating '-' (dash) in probe names with '__' (two consecutive underscores). Reviewed by: markj MFC after: 3 weeks
2013-11-26 08:46:27 +00:00
SDT_PROBE0(sched, , , remain__cpu);
Implement the DTrace sched provider. This implementation aims to be compatible with the sched provider implemented by Solaris and its open- source derivatives. Full documentation of the sched provider can be found on Oracle's DTrace wiki pages. Note that for compatibility with scripts originally written for Solaris, serveral probes are defined that will never fire. These probes are defined to fire when Solaris-specific features perform certain actions. As these features are not present in FreeBSD, the probes can never fire. Also, I have added a two probes that are not defined in Solaris, lend-pri and load-change. These probes have been added to make it possible to collect schedgraph data with DTrace. Finally, a few probes are defined in Solaris to take a cpuinfo_t * argument. As it was not immediately clear to me how to translate that to FreeBSD, currently those probes are passed NULL in place of a cpuinfo_t *. Sponsored by: Sandvine Incorporated MFC after: 2 weeks
2012-05-15 01:30:25 +00:00
}
move thread switch tracing from mi_switch to sched_switch This is done so that the thread state changes during the switch are not confused with the thread state changes reported when the thread spins on a lock. Here is an example, three consecutive entries for the same thread (from top to bottom): KTRGRAPH group:"thread", id:"zio_write_intr_3 tid 100260", state:"sleep", attributes: prio:84, wmesg:"-", lockname:"(null)" KTRGRAPH group:"thread", id:"zio_write_intr_3 tid 100260", state:"spinning", attributes: lockname:"sched lock 1" KTRGRAPH group:"thread", id:"zio_write_intr_3 tid 100260", state:"running", attributes: none The above trace could leave an impression that the final state of the thread was "running". After this change the sleep state will be reported after the "spinning" and "running" states reported for the sched lock. Reviewed by: jhb, markj MFC after: 1 week Sponsored by: Panzura Differential Revision: https://reviews.freebsd.org/D9961
2017-03-23 08:57:04 +00:00
KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "running",
"prio:%d", td->td_priority);
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
/*
* Assert that all went well and return.
*/
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
TDQ_LOCK_ASSERT(tdq, MA_OWNED|MA_NOTRECURSED);
MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
td->td_oncpu = cpuid;
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
}
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* Adjust thread priorities as a result of a nice request.
*/
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
void
Nice, is a property of a process as a whole.. I mistakenly moved it to the ksegroup when breaking up the process structure. Put it back in the proc structure.
2004-06-16 00:26:31 +00:00
sched_nice(struct proc *p, int nice)
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
{
struct thread *td;
Nice, is a property of a process as a whole.. I mistakenly moved it to the ksegroup when breaking up the process structure. Put it back in the proc structure.
2004-06-16 00:26:31 +00:00
PROC_LOCK_ASSERT(p, MA_OWNED);
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
Nice, is a property of a process as a whole.. I mistakenly moved it to the ksegroup when breaking up the process structure. Put it back in the proc structure.
2004-06-16 00:26:31 +00:00
p->p_nice = nice;
Make KSE a kernel option, turned on by default in all GENERIC kernel configs except sun4v (which doesn't process signals properly with KSE). Reviewed by: davidxu@
2006-10-26 21:42:22 +00:00
FOREACH_THREAD_IN_PROC(p, td) {
Commit 1/14 of sched_lock decomposition. - Move all scheduler locking into the schedulers utilizing a technique similar to solaris's container locking. - A per-process spinlock is now used to protect the queue of threads, thread count, suspension count, p_sflags, and other process related scheduling fields. - The new thread lock is actually a pointer to a spinlock for the container that the thread is currently owned by. The container may be a turnstile, sleepqueue, or run queue. - thread_lock() is now used to protect access to thread related scheduling fields. thread_unlock() unlocks the lock and thread_set_lock() implements the transition from one lock to another. - A new "blocked_lock" is used in cases where it is not safe to hold the actual thread's lock yet we must prevent access to the thread. - sched_throw() and sched_fork_exit() are introduced to allow the schedulers to fix-up locking at these points. - Add some minor infrastructure for optionally exporting scheduler statistics that were invaluable in solving performance problems with this patch. Generally these statistics allow you to differentiate between different causes of context switches. Tested by: kris, current@ Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc. Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:50:30 +00:00
thread_lock(td);
Make KSE a kernel option, turned on by default in all GENERIC kernel configs except sun4v (which doesn't process signals properly with KSE). Reviewed by: davidxu@
2006-10-26 21:42:22 +00:00
sched_priority(td);
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
sched_prio(td, td->td_base_user_pri);
Commit 1/14 of sched_lock decomposition. - Move all scheduler locking into the schedulers utilizing a technique similar to solaris's container locking. - A per-process spinlock is now used to protect the queue of threads, thread count, suspension count, p_sflags, and other process related scheduling fields. - The new thread lock is actually a pointer to a spinlock for the container that the thread is currently owned by. The container may be a turnstile, sleepqueue, or run queue. - thread_lock() is now used to protect access to thread related scheduling fields. thread_unlock() unlocks the lock and thread_set_lock() implements the transition from one lock to another. - A new "blocked_lock" is used in cases where it is not safe to hold the actual thread's lock yet we must prevent access to the thread. - sched_throw() and sched_fork_exit() are introduced to allow the schedulers to fix-up locking at these points. - Add some minor infrastructure for optionally exporting scheduler statistics that were invaluable in solving performance problems with this patch. Generally these statistics allow you to differentiate between different causes of context switches. Tested by: kris, current@ Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc. Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:50:30 +00:00
thread_unlock(td);
Nice, is a property of a process as a whole.. I mistakenly moved it to the ksegroup when breaking up the process structure. Put it back in the proc structure.
2004-06-16 00:26:31 +00:00
}
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
}
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* Record the sleep time for the interactivity scorer.
*/
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
void
- Pass the priority argument from *sleep() into sleepq and down into sched_sleep(). This removes extra thread_lock() acquisition and allows the scheduler to decide what to do with the static boost. - Change the priority arguments to cv_* to match sleepq/msleep/etc. where 0 means no priority change. Catch -1 in cv_broadcastpri() and convert it to 0 for now. - Set a flag when sleeping in a way that is compatible with swapping since direct priority comparisons are meaningless now. - Add a sysctl to ule, kern.sched.static_boost, that defaults to on which controls the boost behavior. Turning it off gives better performance in some workloads but needs more investigation. - While we're modifying sleepq, change signal and broadcast to both return with the lock held as the lock was held on enter. Reviewed by: jhb, peter
2008-03-12 06:31:06 +00:00
sched_sleep(struct thread *td, int prio)
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
{
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
Commit 1/14 of sched_lock decomposition. - Move all scheduler locking into the schedulers utilizing a technique similar to solaris's container locking. - A per-process spinlock is now used to protect the queue of threads, thread count, suspension count, p_sflags, and other process related scheduling fields. - The new thread lock is actually a pointer to a spinlock for the container that the thread is currently owned by. The container may be a turnstile, sleepqueue, or run queue. - thread_lock() is now used to protect access to thread related scheduling fields. thread_unlock() unlocks the lock and thread_set_lock() implements the transition from one lock to another. - A new "blocked_lock" is used in cases where it is not safe to hold the actual thread's lock yet we must prevent access to the thread. - sched_throw() and sched_fork_exit() are introduced to allow the schedulers to fix-up locking at these points. - Add some minor infrastructure for optionally exporting scheduler statistics that were invaluable in solving performance problems with this patch. Generally these statistics allow you to differentiate between different causes of context switches. Tested by: kris, current@ Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc. Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:50:30 +00:00
THREAD_LOCK_ASSERT(td, MA_OWNED);
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
- Redefine p_swtime and td_slptime as p_swtick and td_slptick. This changes the units from seconds to the value of 'ticks' when swapped in/out. ULE does not have a periodic timer that scans all threads in the system and as such maintaining a per-second counter is difficult. - Change computations requiring the unit in seconds to subtract ticks and divide by hz. This does make the wraparound condition hz times more frequent but this is still in the range of several months to years and the adverse effects are minimal. Approved by: re
2007-09-21 04:10:23 +00:00
td->td_slptick = ticks;
Allow swap out of the kernel stack for the thread with priority greater or equial then PSOCK, not less or equial. Higher priority has lesser numerical value. Existing test does not allow for swapout of the thread waiting for advisory lock, for exiting child or sleeping for timeout. On the other hand, high-priority waiters of VFS/VM events can be swapped out. Tested by: pho Reviewed by: jhb MFC after: 1 week
2009-12-31 18:52:58 +00:00
if (TD_IS_SUSPENDED(td) || prio >= PSOCK)
- Pass the priority argument from *sleep() into sleepq and down into sched_sleep(). This removes extra thread_lock() acquisition and allows the scheduler to decide what to do with the static boost. - Change the priority arguments to cv_* to match sleepq/msleep/etc. where 0 means no priority change. Catch -1 in cv_broadcastpri() and convert it to 0 for now. - Set a flag when sleeping in a way that is compatible with swapping since direct priority comparisons are meaningless now. - Add a sysctl to ule, kern.sched.static_boost, that defaults to on which controls the boost behavior. Turning it off gives better performance in some workloads but needs more investigation. - While we're modifying sleepq, change signal and broadcast to both return with the lock held as the lock was held on enter. Reviewed by: jhb, peter
2008-03-12 06:31:06 +00:00
td->td_flags |= TDF_CANSWAP;
Rework realtime priority support: - Move the realtime priority range up above kernel sleep priorities and just below interrupt thread priorities. - Contract the interrupt and kernel sleep priority ranges a bit so that the timesharing priority band can be increased. The new timeshare range is now slightly larger than the old realtime + timeshare ranges. - Change the ULE scheduler to no longer use realtime priorities for interactive threads. Instead, the larger timeshare range is now split into separate subranges for interactive and non-interactive ("batch") threads. The end result is that interactive threads and non-interactive threads still use the same priority ranges as before, but realtime threads now have a separate, dedicated priority range. - Do not modify the priority of non-timeshare threads in sched_sleep() or via cv_broadcastpri(). Realtime and idle priority threads will no longer have their priorities affected by sleeping in the kernel. Reviewed by: jeff
2011-01-14 17:06:54 +00:00
if (PRI_BASE(td->td_pri_class) != PRI_TIMESHARE)
return;
- Allow static_boost to specify no boost with '0', traditional kernel fixed pri boost with '1' or any priority less than the current thread's priority with a value greater than two. Default the boost to PRI_MIN_TIMESHARE to prevent regular user-space threads from starving threads in the kernel. This prevents these user-threads from also being scheduled as if they are high fixed-priority kernel threads. - Restore the setting of lowpri in tdq_choose(). It has to be either here or in sched_switch(). I accidentally removed it from both places. Tested by: kris
2008-04-04 01:16:18 +00:00
if (static_boost == 1 && prio)
- Pass the priority argument from *sleep() into sleepq and down into sched_sleep(). This removes extra thread_lock() acquisition and allows the scheduler to decide what to do with the static boost. - Change the priority arguments to cv_* to match sleepq/msleep/etc. where 0 means no priority change. Catch -1 in cv_broadcastpri() and convert it to 0 for now. - Set a flag when sleeping in a way that is compatible with swapping since direct priority comparisons are meaningless now. - Add a sysctl to ule, kern.sched.static_boost, that defaults to on which controls the boost behavior. Turning it off gives better performance in some workloads but needs more investigation. - While we're modifying sleepq, change signal and broadcast to both return with the lock held as the lock was held on enter. Reviewed by: jhb, peter
2008-03-12 06:31:06 +00:00
sched_prio(td, prio);
- Allow static_boost to specify no boost with '0', traditional kernel fixed pri boost with '1' or any priority less than the current thread's priority with a value greater than two. Default the boost to PRI_MIN_TIMESHARE to prevent regular user-space threads from starving threads in the kernel. This prevents these user-threads from also being scheduled as if they are high fixed-priority kernel threads. - Restore the setting of lowpri in tdq_choose(). It has to be either here or in sched_switch(). I accidentally removed it from both places. Tested by: kris
2008-04-04 01:16:18 +00:00
else if (static_boost && td->td_priority > static_boost)
sched_prio(td, static_boost);
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
}
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* Schedule a thread to resume execution and record how long it voluntarily
* slept. We also update the pctcpu, interactivity, and priority.
*/
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
void
sched_wakeup(struct thread *td)
{
- Get rid of the unused DIDRUN flag. This was really only present to support sched_4bsd. - Rename the KTR level for non schedgraph parsed events. They take event space from things we'd like to graph. - Reset our slice value after we sleep. The slice is simply there to prevent starvation among equal priorities. A thread which had almost exhausted it's slice and then slept doesn't need to be rescheduled a tick after it wakes up. - Set the maximum slice value to a more conservative 100ms now that it is more accurately enforced.
2007-01-25 19:14:11 +00:00
struct td_sched *ts;
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
int slptick;
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
Commit 1/14 of sched_lock decomposition. - Move all scheduler locking into the schedulers utilizing a technique similar to solaris's container locking. - A per-process spinlock is now used to protect the queue of threads, thread count, suspension count, p_sflags, and other process related scheduling fields. - The new thread lock is actually a pointer to a spinlock for the container that the thread is currently owned by. The container may be a turnstile, sleepqueue, or run queue. - thread_lock() is now used to protect access to thread related scheduling fields. thread_unlock() unlocks the lock and thread_set_lock() implements the transition from one lock to another. - A new "blocked_lock" is used in cases where it is not safe to hold the actual thread's lock yet we must prevent access to the thread. - sched_throw() and sched_fork_exit() are introduced to allow the schedulers to fix-up locking at these points. - Add some minor infrastructure for optionally exporting scheduler statistics that were invaluable in solving performance problems with this patch. Generally these statistics allow you to differentiate between different causes of context switches. Tested by: kris, current@ Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc. Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:50:30 +00:00
THREAD_LOCK_ASSERT(td, MA_OWNED);
Get rid of struct proc p_sched and struct thread td_sched pointers. p_sched is unused. The struct td_sched is always co-allocated with the struct thread, except for the thread0. Avoid useless indirection, instead calculate td_sched location using simple pointer arithmetic in td_get_sched(9). For thread0, which is statically allocated, create a structure to emulate layout of the dynamic allocation. Reviewed by: jhb (previous version) Sponsored by: The FreeBSD Foundation Differential revision: https://reviews.freebsd.org/D6711
2016-06-05 17:04:03 +00:00
ts = td_get_sched(td);
- Pass the priority argument from *sleep() into sleepq and down into sched_sleep(). This removes extra thread_lock() acquisition and allows the scheduler to decide what to do with the static boost. - Change the priority arguments to cv_* to match sleepq/msleep/etc. where 0 means no priority change. Catch -1 in cv_broadcastpri() and convert it to 0 for now. - Set a flag when sleeping in a way that is compatible with swapping since direct priority comparisons are meaningless now. - Add a sysctl to ule, kern.sched.static_boost, that defaults to on which controls the boost behavior. Turning it off gives better performance in some workloads but needs more investigation. - While we're modifying sleepq, change signal and broadcast to both return with the lock held as the lock was held on enter. Reviewed by: jhb, peter
2008-03-12 06:31:06 +00:00
td->td_flags &= ~TDF_CANSWAP;
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
/*
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
* If we slept for more than a tick update our interactivity and
* priority.
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
*/
- Redefine p_swtime and td_slptime as p_swtick and td_slptick. This changes the units from seconds to the value of 'ticks' when swapped in/out. ULE does not have a periodic timer that scans all threads in the system and as such maintaining a per-second counter is difficult. - Change computations requiring the unit in seconds to subtract ticks and divide by hz. This does make the wraparound condition hz times more frequent but this is still in the range of several months to years and the adverse effects are minimal. Approved by: re
2007-09-21 04:10:23 +00:00
slptick = td->td_slptick;
td->td_slptick = 0;
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
if (slptick && slptick != ticks) {
Rewrite thread CPU usage percentage math to not depend on periodic calls with HZ rate through the sched_tick() calls from hardclock(). Potentially it can be used to improve precision, but now it is just minus one more reason to call hardclock() for every HZ tick on every active CPU. SCHED_4BSD never used sched_tick(), but keep it in place for now, as at least SCHED_FBFS existing in patches out of the tree depends on it. MFC after: 1 month
2012-03-13 08:18:54 +00:00
ts->ts_slptime += (ticks - slptick) << SCHED_TICK_SHIFT;
- Fix a comparison in sched_choose() that caused cpus to be constantly marked idle, thus breaking cpu load balancing. - Change sched_interact_update() to fix cases where the stored history has expanded significantly rather than handling them in the callers. This fixes a case where sched_priority() could compute a bad value. - Add a sysctl to disable the global load balancer for experimentation.
2007-01-05 23:45:38 +00:00
sched_interact_update(td);
Rewrite thread CPU usage percentage math to not depend on periodic calls with HZ rate through the sched_tick() calls from hardclock(). Potentially it can be used to improve precision, but now it is just minus one more reason to call hardclock() for every HZ tick on every active CPU. SCHED_4BSD never used sched_tick(), but keep it in place for now, as at least SCHED_FBFS existing in patches out of the tree depends on it. MFC after: 1 month
2012-03-13 08:18:54 +00:00
sched_pctcpu_update(ts, 0);
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
}
- Change ULE to use dynamic slice sizes for the timeshare queue in order to further reduce latency for threads in this queue. This should help as threads transition from realtime to timeshare. The latency is bound to a max of sched_slice until we have more than sched_slice / 6 threads runnable. Then the min slice is allotted to all threads and latency becomes (nthreads - 1) * min_slice. Discussed with: mav
2012-11-08 01:46:47 +00:00
/*
* Reset the slice value since we slept and advanced the round-robin.
*/
ts->ts_slice = 0;
- Catch up to setrunqueue/choosethread/etc. api changes. - Define our own maybe_preempt() as sched_preempt(). We want to be able to preempt idlethread in all cases. - Define our idlethread to require preemption to exit. - Get the cpu estimation tick from sched_tick() so we don't have to worry about errors from a sampling interval that differs from the time domain. This was the source of sched_priority prints/panics and inaccurate pctcpu display in top.
2007-01-23 08:50:34 +00:00
sched_add(td, SRQ_BORING);
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
}
/*
* Penalize the parent for creating a new child and initialize the child's
* priority.
*/
void
Make KSE a kernel option, turned on by default in all GENERIC kernel configs except sun4v (which doesn't process signals properly with KSE). Reviewed by: davidxu@
2006-10-26 21:42:22 +00:00
sched_fork(struct thread *td, struct thread *child)
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
{
Commit 1/14 of sched_lock decomposition. - Move all scheduler locking into the schedulers utilizing a technique similar to solaris's container locking. - A per-process spinlock is now used to protect the queue of threads, thread count, suspension count, p_sflags, and other process related scheduling fields. - The new thread lock is actually a pointer to a spinlock for the container that the thread is currently owned by. The container may be a turnstile, sleepqueue, or run queue. - thread_lock() is now used to protect access to thread related scheduling fields. thread_unlock() unlocks the lock and thread_set_lock() implements the transition from one lock to another. - A new "blocked_lock" is used in cases where it is not safe to hold the actual thread's lock yet we must prevent access to the thread. - sched_throw() and sched_fork_exit() are introduced to allow the schedulers to fix-up locking at these points. - Add some minor infrastructure for optionally exporting scheduler statistics that were invaluable in solving performance problems with this patch. Generally these statistics allow you to differentiate between different causes of context switches. Tested by: kris, current@ Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc. Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:50:30 +00:00
THREAD_LOCK_ASSERT(td, MA_OWNED);
Get rid of struct proc p_sched and struct thread td_sched pointers. p_sched is unused. The struct td_sched is always co-allocated with the struct thread, except for the thread0. Avoid useless indirection, instead calculate td_sched location using simple pointer arithmetic in td_get_sched(9). For thread0, which is statically allocated, create a structure to emulate layout of the dynamic allocation. Reviewed by: jhb (previous version) Sponsored by: The FreeBSD Foundation Differential revision: https://reviews.freebsd.org/D6711
2016-06-05 17:04:03 +00:00
sched_pctcpu_update(td_get_sched(td), 1);
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
sched_fork_thread(td, child);
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
/*
* Penalize the parent and child for forking.
*/
sched_interact_fork(child);
sched_priority(child);
Get rid of struct proc p_sched and struct thread td_sched pointers. p_sched is unused. The struct td_sched is always co-allocated with the struct thread, except for the thread0. Avoid useless indirection, instead calculate td_sched location using simple pointer arithmetic in td_get_sched(9). For thread0, which is statically allocated, create a structure to emulate layout of the dynamic allocation. Reviewed by: jhb (previous version) Sponsored by: The FreeBSD Foundation Differential revision: https://reviews.freebsd.org/D6711
2016-06-05 17:04:03 +00:00
td_get_sched(td)->ts_runtime += tickincr;
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
sched_interact_update(td);
sched_priority(td);
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
}
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* Fork a new thread, may be within the same process.
*/
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
void
sched_fork_thread(struct thread *td, struct thread *child)
{
struct td_sched *ts;
struct td_sched *ts2;
- Change ULE to use dynamic slice sizes for the timeshare queue in order to further reduce latency for threads in this queue. This should help as threads transition from realtime to timeshare. The latency is bound to a max of sched_slice until we have more than sched_slice / 6 threads runnable. Then the min slice is allotted to all threads and latency becomes (nthreads - 1) * min_slice. Discussed with: mav
2012-11-08 01:46:47 +00:00
struct tdq *tdq;
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
- Change ULE to use dynamic slice sizes for the timeshare queue in order to further reduce latency for threads in this queue. This should help as threads transition from realtime to timeshare. The latency is bound to a max of sched_slice until we have more than sched_slice / 6 threads runnable. Then the min slice is allotted to all threads and latency becomes (nthreads - 1) * min_slice. Discussed with: mav
2012-11-08 01:46:47 +00:00
tdq = TDQ_SELF();
- ULE and 4BSD share only one line of code from sched_newthread() so implement the required pieces in sched_fork_thread(). The td_sched pointer is already setup by thread_init anyway.
2008-03-20 03:06:33 +00:00
THREAD_LOCK_ASSERT(td, MA_OWNED);
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
/*
* Initialize child.
*/
Get rid of struct proc p_sched and struct thread td_sched pointers. p_sched is unused. The struct td_sched is always co-allocated with the struct thread, except for the thread0. Avoid useless indirection, instead calculate td_sched location using simple pointer arithmetic in td_get_sched(9). For thread0, which is statically allocated, create a structure to emulate layout of the dynamic allocation. Reviewed by: jhb (previous version) Sponsored by: The FreeBSD Foundation Differential revision: https://reviews.freebsd.org/D6711
2016-06-05 17:04:03 +00:00
ts = td_get_sched(td);
ts2 = td_get_sched(child);
kgdb uses td_oncpu to determine if a thread is running and should use a pcb from stoppcbs[] rather than the thread's PCB. However, exited threads retained td_oncpu from the last time they ran, and newborn threads had their CPU fields cleared to zero during fork and thread creation since they are in the set of fields zeroed when threads are setup. To fix, explicitly update the CPU fields for exiting threads in sched_throw() to reflect the switch out and reset the CPU fields for new threads in sched_fork_thread() to NOCPU. Reviewed by: kib MFC after: 1 week Differential Revision: https://reviews.freebsd.org/D3193
2015-08-03 20:43:36 +00:00
child->td_oncpu = NOCPU;
child->td_lastcpu = NOCPU;
- Change ULE to use dynamic slice sizes for the timeshare queue in order to further reduce latency for threads in this queue. This should help as threads transition from realtime to timeshare. The latency is bound to a max of sched_slice until we have more than sched_slice / 6 threads runnable. Then the min slice is allotted to all threads and latency becomes (nthreads - 1) * min_slice. Discussed with: mav
2012-11-08 01:46:47 +00:00
child->td_lock = TDQ_LOCKPTR(tdq);
- ULE and 4BSD share only one line of code from sched_newthread() so implement the required pieces in sched_fork_thread(). The td_sched pointer is already setup by thread_init anyway.
2008-03-20 03:06:33 +00:00
child->td_cpuset = cpuset_ref(td->td_cpuset);
Implement 'domainset', a cpuset based NUMA policy mechanism. This allows userspace to control NUMA policy administratively and programmatically. Implement domainset based iterators in the page layer. Remove the now legacy numa_* syscalls. Cleanup some header polution created by having seq.h in proc.h. Reviewed by: markj, kib Discussed with: alc Tested by: pho Sponsored by: Netflix, Dell/EMC Isilon Differential Revision: https://reviews.freebsd.org/D13403
2018-01-12 22:48:23 +00:00
child->td_domain.dr_policy = td->td_cpuset->cs_domain;
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
ts2->ts_cpu = ts->ts_cpu;
- ULE and 4BSD share only one line of code from sched_newthread() so implement the required pieces in sched_fork_thread(). The td_sched pointer is already setup by thread_init anyway.
2008-03-20 03:06:33 +00:00
ts2->ts_flags = 0;
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
/*
- Move sched_fork() later in fork() after the various sections of the new thread and proc have been copied and zeroed from the old thread and proc. Otherwise attempts to modify thread or process data in sched_fork() could be undone. - Don't copy td_{base,}_user_pri from the old thread to the new thread in sched_fork_thread() in ULE. This is already done courtesy the bcopy() of the thread copy region. - Always initialize the real priority (td_priority) of new threads to the new thread's base priority (td_base_pri) to avoid bogusly inheriting a borrowed priority from the parent thread. MFC after: 2 weeks
2011-01-06 22:24:00 +00:00
* Grab our parents cpu estimation information.
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
*/
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
ts2->ts_ticks = ts->ts_ticks;
ts2->ts_ltick = ts->ts_ltick;
ts2->ts_ftick = ts->ts_ftick;
- Move sched_fork() later in fork() after the various sections of the new thread and proc have been copied and zeroed from the old thread and proc. Otherwise attempts to modify thread or process data in sched_fork() could be undone. - Don't copy td_{base,}_user_pri from the old thread to the new thread in sched_fork_thread() in ULE. This is already done courtesy the bcopy() of the thread copy region. - Always initialize the real priority (td_priority) of new threads to the new thread's base priority (td_base_pri) to avoid bogusly inheriting a borrowed priority from the parent thread. MFC after: 2 weeks
2011-01-06 22:24:00 +00:00
/*
* Do not inherit any borrowed priority from the parent.
*/
child->td_priority = child->td_base_pri;
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
/*
* And update interactivity score.
*/
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
ts2->ts_slptime = ts->ts_slptime;
ts2->ts_runtime = ts->ts_runtime;
- Change ULE to use dynamic slice sizes for the timeshare queue in order to further reduce latency for threads in this queue. This should help as threads transition from realtime to timeshare. The latency is bound to a max of sched_slice until we have more than sched_slice / 6 threads runnable. Then the min slice is allotted to all threads and latency becomes (nthreads - 1) * min_slice. Discussed with: mav
2012-11-08 01:46:47 +00:00
/* Attempt to quickly learn interactivity. */
ts2->ts_slice = tdq_slice(tdq) - sched_slice_min;
- Implement generic macros for producing KTR records that are compatible with src/tools/sched/schedgraph.py. This allows developers to quickly create a graphical view of ktr data for any resource in the system. - Add sched_tdname() and the pcpu field 'name' for quickly and uniformly identifying records associated with a thread or cpu. - Reimplement the KTR_SCHED traces using the new generic facility. Obtained from: attilio Discussed with: jhb Sponsored by: Nokia
2009-01-17 07:17:57 +00:00
#ifdef KTR
bzero(ts2->ts_name, sizeof(ts2->ts_name));
#endif
- Add a SYSCTL node for the ule scheduler. - Allow user adjustable min and max time slices (suggested by hiten). - Change the SLP_RUN_MAX to 100ms from 2 seconds so that we learn whether a process is interactive or not much more quickly. - Place a process on the current run queue if it is interactive or if it is running at an interrupt thread priority due to priority prop. - Use the 'current' timeshare queue for interrupt threads, realtime threads, and idle threads that are running at higher priority due to priority prop. This fixes problems where priorities would have been elevated but we would not check the timeshare run queue until other lower priority tasks were no longer runnable. - Keep an array of loads indexed by the priority class as well as a global load. - Keep an bucket of nice values with a count of the number of kses currently runnable with that nice value. - Keep track of the minimum nice value of any running thread. - Remove the unused short term sleep accounting. I was attempting to use this for load balancing but it didn't work out. - Define a kseq_print() for use with debugging. - Add KTR debugging at useful places so we can easily debug slice and priority assignment. - Decouple the runq assignment from the kseq assignment. kseq_add now keeps track of statistics. This is done so that the nice and load is still tracked for the currently running process. Previously if a niced process was added while a non nice process was running the niced process would still get a slice since it was not aware of the unnice process. - Make adjustments for the sched api changes.
2003-04-11 03:47:14 +00:00
}
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* Adjust the priority class of a thread.
*/
- Add a SYSCTL node for the ule scheduler. - Allow user adjustable min and max time slices (suggested by hiten). - Change the SLP_RUN_MAX to 100ms from 2 seconds so that we learn whether a process is interactive or not much more quickly. - Place a process on the current run queue if it is interactive or if it is running at an interrupt thread priority due to priority prop. - Use the 'current' timeshare queue for interrupt threads, realtime threads, and idle threads that are running at higher priority due to priority prop. This fixes problems where priorities would have been elevated but we would not check the timeshare run queue until other lower priority tasks were no longer runnable. - Keep an array of loads indexed by the priority class as well as a global load. - Keep an bucket of nice values with a count of the number of kses currently runnable with that nice value. - Keep track of the minimum nice value of any running thread. - Remove the unused short term sleep accounting. I was attempting to use this for load balancing but it didn't work out. - Define a kseq_print() for use with debugging. - Add KTR debugging at useful places so we can easily debug slice and priority assignment. - Decouple the runq assignment from the kseq assignment. kseq_add now keeps track of statistics. This is done so that the nice and load is still tracked for the currently running process. Previously if a niced process was added while a non nice process was running the niced process would still get a slice since it was not aware of the unnice process. - Make adjustments for the sched api changes.
2003-04-11 03:47:14 +00:00
void
Make KSE a kernel option, turned on by default in all GENERIC kernel configs except sun4v (which doesn't process signals properly with KSE). Reviewed by: davidxu@
2006-10-26 21:42:22 +00:00
sched_class(struct thread *td, int class)
- Add a SYSCTL node for the ule scheduler. - Allow user adjustable min and max time slices (suggested by hiten). - Change the SLP_RUN_MAX to 100ms from 2 seconds so that we learn whether a process is interactive or not much more quickly. - Place a process on the current run queue if it is interactive or if it is running at an interrupt thread priority due to priority prop. - Use the 'current' timeshare queue for interrupt threads, realtime threads, and idle threads that are running at higher priority due to priority prop. This fixes problems where priorities would have been elevated but we would not check the timeshare run queue until other lower priority tasks were no longer runnable. - Keep an array of loads indexed by the priority class as well as a global load. - Keep an bucket of nice values with a count of the number of kses currently runnable with that nice value. - Keep track of the minimum nice value of any running thread. - Remove the unused short term sleep accounting. I was attempting to use this for load balancing but it didn't work out. - Define a kseq_print() for use with debugging. - Add KTR debugging at useful places so we can easily debug slice and priority assignment. - Decouple the runq assignment from the kseq assignment. kseq_add now keeps track of statistics. This is done so that the nice and load is still tracked for the currently running process. Previously if a niced process was added while a non nice process was running the niced process would still get a slice since it was not aware of the unnice process. - Make adjustments for the sched api changes.
2003-04-11 03:47:14 +00:00
{
Commit 1/14 of sched_lock decomposition. - Move all scheduler locking into the schedulers utilizing a technique similar to solaris's container locking. - A per-process spinlock is now used to protect the queue of threads, thread count, suspension count, p_sflags, and other process related scheduling fields. - The new thread lock is actually a pointer to a spinlock for the container that the thread is currently owned by. The container may be a turnstile, sleepqueue, or run queue. - thread_lock() is now used to protect access to thread related scheduling fields. thread_unlock() unlocks the lock and thread_set_lock() implements the transition from one lock to another. - A new "blocked_lock" is used in cases where it is not safe to hold the actual thread's lock yet we must prevent access to the thread. - sched_throw() and sched_fork_exit() are introduced to allow the schedulers to fix-up locking at these points. - Add some minor infrastructure for optionally exporting scheduler statistics that were invaluable in solving performance problems with this patch. Generally these statistics allow you to differentiate between different causes of context switches. Tested by: kris, current@ Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc. Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:50:30 +00:00
THREAD_LOCK_ASSERT(td, MA_OWNED);
Make KSE a kernel option, turned on by default in all GENERIC kernel configs except sun4v (which doesn't process signals properly with KSE). Reviewed by: davidxu@
2006-10-26 21:42:22 +00:00
if (td->td_pri_class == class)
- Add a SYSCTL node for the ule scheduler. - Allow user adjustable min and max time slices (suggested by hiten). - Change the SLP_RUN_MAX to 100ms from 2 seconds so that we learn whether a process is interactive or not much more quickly. - Place a process on the current run queue if it is interactive or if it is running at an interrupt thread priority due to priority prop. - Use the 'current' timeshare queue for interrupt threads, realtime threads, and idle threads that are running at higher priority due to priority prop. This fixes problems where priorities would have been elevated but we would not check the timeshare run queue until other lower priority tasks were no longer runnable. - Keep an array of loads indexed by the priority class as well as a global load. - Keep an bucket of nice values with a count of the number of kses currently runnable with that nice value. - Keep track of the minimum nice value of any running thread. - Remove the unused short term sleep accounting. I was attempting to use this for load balancing but it didn't work out. - Define a kseq_print() for use with debugging. - Add KTR debugging at useful places so we can easily debug slice and priority assignment. - Decouple the runq assignment from the kseq assignment. kseq_add now keeps track of statistics. This is done so that the nice and load is still tracked for the currently running process. Previously if a niced process was added while a non nice process was running the niced process would still get a slice since it was not aware of the unnice process. - Make adjustments for the sched api changes.
2003-04-11 03:47:14 +00:00
return;
Make KSE a kernel option, turned on by default in all GENERIC kernel configs except sun4v (which doesn't process signals properly with KSE). Reviewed by: davidxu@
2006-10-26 21:42:22 +00:00
td->td_pri_class = class;
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
}
/*
* Return some of the child's priority and interactivity to the parent.
*/
void
Changes to try fix sched_ule.c courtesy of David Xu.
2006-12-06 06:55:59 +00:00
sched_exit(struct proc *p, struct thread *child)
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
{
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
struct thread *td;
Make KSE a kernel option, turned on by default in all GENERIC kernel configs except sun4v (which doesn't process signals properly with KSE). Reviewed by: davidxu@
2006-10-26 21:42:22 +00:00
- Implement generic macros for producing KTR records that are compatible with src/tools/sched/schedgraph.py. This allows developers to quickly create a graphical view of ktr data for any resource in the system. - Add sched_tdname() and the pcpu field 'name' for quickly and uniformly identifying records associated with a thread or cpu. - Reimplement the KTR_SCHED traces using the new generic facility. Obtained from: attilio Discussed with: jhb Sponsored by: Nokia
2009-01-17 07:17:57 +00:00
KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "proc exit",
Fix format strings for KTR_STATE in 4BSD ad ULE schedulers. Submitted by: Ivan Klymenko <fidaj@ukr.net> PR: kern/159904, kern/159905 MFC after: 2 weeks Approved by: re (kib)
2011-08-26 18:00:07 +00:00
"prio:%d", child->td_priority);
- Relax requirements for p_numthreads, p_threads, p_swtick, and p_nice from requiring the per-process spinlock to only requiring the process lock. - Reflect these changes in the proc.h documentation and consumers throughout the kernel. This is a substantial reduction in locking cost for these fields and was made possible by recent changes to threading support.
2008-03-19 06:19:01 +00:00
PROC_LOCK_ASSERT(p, MA_OWNED);
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
td = FIRST_THREAD_IN_PROC(p);
sched_exit_thread(td, child);
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
}
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* Penalize another thread for the time spent on this one. This helps to
* worsen the priority and interactivity of processes which schedule batch
* jobs such as make. This has little effect on the make process itself but
* causes new processes spawned by it to receive worse scores immediately.
*/
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
void
Changes to try fix sched_ule.c courtesy of David Xu.
2006-12-06 06:55:59 +00:00
sched_exit_thread(struct thread *td, struct thread *child)
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
{
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
- Implement generic macros for producing KTR records that are compatible with src/tools/sched/schedgraph.py. This allows developers to quickly create a graphical view of ktr data for any resource in the system. - Add sched_tdname() and the pcpu field 'name' for quickly and uniformly identifying records associated with a thread or cpu. - Reimplement the KTR_SCHED traces using the new generic facility. Obtained from: attilio Discussed with: jhb Sponsored by: Nokia
2009-01-17 07:17:57 +00:00
KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "thread exit",
Fix format strings for KTR_STATE in 4BSD ad ULE schedulers. Submitted by: Ivan Klymenko <fidaj@ukr.net> PR: kern/159904, kern/159905 MFC after: 2 weeks Approved by: re (kib)
2011-08-26 18:00:07 +00:00
"prio:%d", child->td_priority);
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
/*
* Give the child's runtime to the parent without returning the
* sleep time as a penalty to the parent. This causes shells that
* launch expensive things to mark their children as expensive.
*/
Commit 1/14 of sched_lock decomposition. - Move all scheduler locking into the schedulers utilizing a technique similar to solaris's container locking. - A per-process spinlock is now used to protect the queue of threads, thread count, suspension count, p_sflags, and other process related scheduling fields. - The new thread lock is actually a pointer to a spinlock for the container that the thread is currently owned by. The container may be a turnstile, sleepqueue, or run queue. - thread_lock() is now used to protect access to thread related scheduling fields. thread_unlock() unlocks the lock and thread_set_lock() implements the transition from one lock to another. - A new "blocked_lock" is used in cases where it is not safe to hold the actual thread's lock yet we must prevent access to the thread. - sched_throw() and sched_fork_exit() are introduced to allow the schedulers to fix-up locking at these points. - Add some minor infrastructure for optionally exporting scheduler statistics that were invaluable in solving performance problems with this patch. Generally these statistics allow you to differentiate between different causes of context switches. Tested by: kris, current@ Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc. Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:50:30 +00:00
thread_lock(td);
Get rid of struct proc p_sched and struct thread td_sched pointers. p_sched is unused. The struct td_sched is always co-allocated with the struct thread, except for the thread0. Avoid useless indirection, instead calculate td_sched location using simple pointer arithmetic in td_get_sched(9). For thread0, which is statically allocated, create a structure to emulate layout of the dynamic allocation. Reviewed by: jhb (previous version) Sponsored by: The FreeBSD Foundation Differential revision: https://reviews.freebsd.org/D6711
2016-06-05 17:04:03 +00:00
td_get_sched(td)->ts_runtime += td_get_sched(child)->ts_runtime;
Changes to try fix sched_ule.c courtesy of David Xu.
2006-12-06 06:55:59 +00:00
sched_interact_update(td);
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
sched_priority(td);
Commit 1/14 of sched_lock decomposition. - Move all scheduler locking into the schedulers utilizing a technique similar to solaris's container locking. - A per-process spinlock is now used to protect the queue of threads, thread count, suspension count, p_sflags, and other process related scheduling fields. - The new thread lock is actually a pointer to a spinlock for the container that the thread is currently owned by. The container may be a turnstile, sleepqueue, or run queue. - thread_lock() is now used to protect access to thread related scheduling fields. thread_unlock() unlocks the lock and thread_set_lock() implements the transition from one lock to another. - A new "blocked_lock" is used in cases where it is not safe to hold the actual thread's lock yet we must prevent access to the thread. - sched_throw() and sched_fork_exit() are introduced to allow the schedulers to fix-up locking at these points. - Add some minor infrastructure for optionally exporting scheduler statistics that were invaluable in solving performance problems with this patch. Generally these statistics allow you to differentiate between different causes of context switches. Tested by: kris, current@ Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc. Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:50:30 +00:00
thread_unlock(td);
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
}
- Add an implementation of sched_preempt() that avoids excessive IPIs. - Normalize the preemption/ipi setting code by introducing sched_shouldpreempt() so the logical is identical and not repeated between tdq_notify() and sched_setpreempt(). - In tdq_notify() don't set NEEDRESCHED as we may not actually own the thread lock this could have caused us to lose td_flags settings. - Garbage collect some tunables that are no longer relevant.
2008-03-10 01:32:01 +00:00
void
sched_preempt(struct thread *td)
{
struct tdq *tdq;
Implement the DTrace sched provider. This implementation aims to be compatible with the sched provider implemented by Solaris and its open- source derivatives. Full documentation of the sched provider can be found on Oracle's DTrace wiki pages. Note that for compatibility with scripts originally written for Solaris, serveral probes are defined that will never fire. These probes are defined to fire when Solaris-specific features perform certain actions. As these features are not present in FreeBSD, the probes can never fire. Also, I have added a two probes that are not defined in Solaris, lend-pri and load-change. These probes have been added to make it possible to collect schedgraph data with DTrace. Finally, a few probes are defined in Solaris to take a cpuinfo_t * argument. As it was not immediately clear to me how to translate that to FreeBSD, currently those probes are passed NULL in place of a cpuinfo_t *. Sponsored by: Sandvine Incorporated MFC after: 2 weeks
2012-05-15 01:30:25 +00:00
SDT_PROBE2(sched, , , surrender, td, td->td_proc);
- Add an implementation of sched_preempt() that avoids excessive IPIs. - Normalize the preemption/ipi setting code by introducing sched_shouldpreempt() so the logical is identical and not repeated between tdq_notify() and sched_setpreempt(). - In tdq_notify() don't set NEEDRESCHED as we may not actually own the thread lock this could have caused us to lose td_flags settings. - Garbage collect some tunables that are no longer relevant.
2008-03-10 01:32:01 +00:00
thread_lock(td);
tdq = TDQ_SELF();
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
tdq->tdq_ipipending = 0;
if (td->td_priority > tdq->tdq_lowpri) {
- Make SCHED_STATS more generic by adding a wrapper to create the variables and sysctl nodes. - In reset walk the children of kern_sched_stats and reset the counters via the oid_arg1 pointer. This allows us to add arbitrary counters to the tree and still reset them properly. - Define a set of switch types to be passed with flags to mi_switch(). These types are named SWT_*. These types correspond to SCHED_STATS counters and are automatically handled in this way. - Make the new SWT_ types more specific than the older switch stats. There are now stats for idle switches, remote idle wakeups, remote preemption ithreads idling, etc. - Add switch statistics for ULE's pickcpu algorithm. These stats include how much migration there is, how often affinity was successful, how often threads were migrated to the local cpu on wakeup, etc. Sponsored by: Nokia
2008-04-17 04:20:10 +00:00
int flags;
flags = SW_INVOL | SW_PREEMPT;
- Add an implementation of sched_preempt() that avoids excessive IPIs. - Normalize the preemption/ipi setting code by introducing sched_shouldpreempt() so the logical is identical and not repeated between tdq_notify() and sched_setpreempt(). - In tdq_notify() don't set NEEDRESCHED as we may not actually own the thread lock this could have caused us to lose td_flags settings. - Garbage collect some tunables that are no longer relevant.
2008-03-10 01:32:01 +00:00
if (td->td_critnest > 1)
td->td_owepreempt = 1;
- Make SCHED_STATS more generic by adding a wrapper to create the variables and sysctl nodes. - In reset walk the children of kern_sched_stats and reset the counters via the oid_arg1 pointer. This allows us to add arbitrary counters to the tree and still reset them properly. - Define a set of switch types to be passed with flags to mi_switch(). These types are named SWT_*. These types correspond to SCHED_STATS counters and are automatically handled in this way. - Make the new SWT_ types more specific than the older switch stats. There are now stats for idle switches, remote idle wakeups, remote preemption ithreads idling, etc. - Add switch statistics for ULE's pickcpu algorithm. These stats include how much migration there is, how often affinity was successful, how often threads were migrated to the local cpu on wakeup, etc. Sponsored by: Nokia
2008-04-17 04:20:10 +00:00
else if (TD_IS_IDLETHREAD(td))
mi_switch(flags | SWT_REMOTEWAKEIDLE, NULL);
- Add an implementation of sched_preempt() that avoids excessive IPIs. - Normalize the preemption/ipi setting code by introducing sched_shouldpreempt() so the logical is identical and not repeated between tdq_notify() and sched_setpreempt(). - In tdq_notify() don't set NEEDRESCHED as we may not actually own the thread lock this could have caused us to lose td_flags settings. - Garbage collect some tunables that are no longer relevant.
2008-03-10 01:32:01 +00:00
else
- Make SCHED_STATS more generic by adding a wrapper to create the variables and sysctl nodes. - In reset walk the children of kern_sched_stats and reset the counters via the oid_arg1 pointer. This allows us to add arbitrary counters to the tree and still reset them properly. - Define a set of switch types to be passed with flags to mi_switch(). These types are named SWT_*. These types correspond to SCHED_STATS counters and are automatically handled in this way. - Make the new SWT_ types more specific than the older switch stats. There are now stats for idle switches, remote idle wakeups, remote preemption ithreads idling, etc. - Add switch statistics for ULE's pickcpu algorithm. These stats include how much migration there is, how often affinity was successful, how often threads were migrated to the local cpu on wakeup, etc. Sponsored by: Nokia
2008-04-17 04:20:10 +00:00
mi_switch(flags | SWT_REMOTEPREEMPT, NULL);
- Add an implementation of sched_preempt() that avoids excessive IPIs. - Normalize the preemption/ipi setting code by introducing sched_shouldpreempt() so the logical is identical and not repeated between tdq_notify() and sched_setpreempt(). - In tdq_notify() don't set NEEDRESCHED as we may not actually own the thread lock this could have caused us to lose td_flags settings. - Garbage collect some tunables that are no longer relevant.
2008-03-10 01:32:01 +00:00
}
thread_unlock(td);
}
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* Fix priorities on return to user-space. Priorities may be elevated due
* to static priorities in msleep() or similar.
*/
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
void
Inlined sched_userret. The tested condition is rarely true and it induces a function call on each return to userspace. Bumps getuid rate by about 1% on Broadwell.
2018-05-07 23:36:16 +00:00
sched_userret_slowpath(struct thread *td)
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
{
Inlined sched_userret. The tested condition is rarely true and it induces a function call on each return to userspace. Bumps getuid rate by about 1% on Broadwell.
2018-05-07 23:36:16 +00:00
thread_lock(td);
td->td_priority = td->td_user_pri;
td->td_base_pri = td->td_user_pri;
tdq_setlowpri(TDQ_SELF(), td);
thread_unlock(td);
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
}
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* Handle a stathz tick. This is really only relevant for timeshare
* threads.
*/
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
void
- Update the sched api. sched_{add,rem,clock,pctcpu} now all accept a td argument rather than a kse.
2003-10-16 08:39:15 +00:00
sched_clock(struct thread *td)
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
{
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
struct tdq *tdq;
struct td_sched *ts;
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
THREAD_LOCK_ASSERT(td, MA_OWNED);
- Only allow the tdq_idx to increase by one each tick rather than up to the most recently chosen index. This significantly improves nice behavior. This allows a lower priority thread to run some multiple of times before the higher priority thread makes it to the front of the queue. A nice +20 cpu hog now only gets ~5% of the cpu when running with a nice 0 cpu hog and about 1.5% with a nice -20 hog. A nice difference of 1 makes a 4% difference in cpu usage between two hogs. - Track a seperate insert and removal index. When the removal index is empty it is updated to point at the current insert index. - Don't remove and re-add a thread to the runq when it is being adjusted down in priority. - Pull some conditional code out of sched_tick(). It's looking a bit large now.
2007-01-04 12:16:19 +00:00
tdq = TDQ_SELF();
- Move the rebalancer back into hardclock to prevent potential softclock starvation caused by unbalanced interrupt loads. - Change the rebalancer to work on stathz ticks but retain randomization. - Simplify locking in tdq_idled() to use the tdq_lock_pair() rather than complex sequences of locks to avoid deadlock. Reported by: kris Approved by: re
2007-10-02 00:36:06 +00:00
#ifdef SMP
/*
* We run the long term load balancer infrequently on the first cpu.
*/
if (balance_tdq == tdq) {
if (balance_ticks && --balance_ticks == 0)
sched_balance();
}
#endif
- Add a metric to describe how busy a processor has been over the last two ticks by counting the number of switches and the load when sched_clock() is called. - If the busy metric exceeds a threshold allow the idle thread to spin waiting for new work for a brief period to avoid using IPIs. This reduces the cost on the sender and receiver as well as reducing wakeup latency considerably when it works. Sponsored by: Nokia
2008-04-17 09:56:01 +00:00
/*
* Save the old switch count so we have a record of the last ticks
* activity. Initialize the new switch count based on our load.
* If there is some activity seed it to reflect that.
*/
tdq->tdq_oldswitchcnt = tdq->tdq_switchcnt;
- Add an integer argument to idle to indicate how likely we are to wake from idle over the next tick. - Add a new MD routine, cpu_wake_idle() to wakeup idle threads who are suspended in cpu specific states. This function can fail and cause the scheduler to fall back to another mechanism (ipi). - Implement support for mwait in cpu_idle() on i386/amd64 machines that support it. mwait is a higher performance way to synchronize cpus as compared to hlt & ipis. - Allow selecting the idle routine by name via sysctl machdep.idle. This replaces machdep.cpu_idle_hlt. Only idle routines supported by the current machine are permitted. Sponsored by: Nokia
2008-04-25 05:18:50 +00:00
tdq->tdq_switchcnt = tdq->tdq_load;
- Use a new flag, KEF_XFERABLE, to record with certainty that this kse had contributed to the transferable load count. This prevents any potential problems with sched_pin() being used around calls to setrunqueue(). - Change the sched_add() load balancing algorithm to try to migrate on wakeup. This attempts to place threads that communicate with each other on the same CPU. - Don't clear the idle counts in kseq_transfer(), let the cpus do that when they call sched_add() from kseq_assign(). - Correct a few out of date comments. - Make sure the ke_cpu field is correct when we preempt. - Call kseq_assign() from sched_clock() to catch any assignments that were done without IPI. Presently all assignments are done with an IPI, but I'm trying a patch that limits that. - Don't migrate a thread if it is still runnable in sched_add(). Previously, this could only happen for KSE threads, but due to changes to sched_switch() all threads went through this path. - Remove some code that was added with preemption but is not necessary.
2004-08-10 07:52:21 +00:00
/*
- Only allow the tdq_idx to increase by one each tick rather than up to the most recently chosen index. This significantly improves nice behavior. This allows a lower priority thread to run some multiple of times before the higher priority thread makes it to the front of the queue. A nice +20 cpu hog now only gets ~5% of the cpu when running with a nice 0 cpu hog and about 1.5% with a nice -20 hog. A nice difference of 1 makes a 4% difference in cpu usage between two hogs. - Track a seperate insert and removal index. When the removal index is empty it is updated to point at the current insert index. - Don't remove and re-add a thread to the runq when it is being adjusted down in priority. - Pull some conditional code out of sched_tick(). It's looking a bit large now.
2007-01-04 12:16:19 +00:00
* Advance the insert index once for each tick to ensure that all
* threads get a chance to run.
- Use a new flag, KEF_XFERABLE, to record with certainty that this kse had contributed to the transferable load count. This prevents any potential problems with sched_pin() being used around calls to setrunqueue(). - Change the sched_add() load balancing algorithm to try to migrate on wakeup. This attempts to place threads that communicate with each other on the same CPU. - Don't clear the idle counts in kseq_transfer(), let the cpus do that when they call sched_add() from kseq_assign(). - Correct a few out of date comments. - Make sure the ke_cpu field is correct when we preempt. - Call kseq_assign() from sched_clock() to catch any assignments that were done without IPI. Presently all assignments are done with an IPI, but I'm trying a patch that limits that. - Don't migrate a thread if it is still runnable in sched_add(). Previously, this could only happen for KSE threads, but due to changes to sched_switch() all threads went through this path. - Remove some code that was added with preemption but is not necessary.
2004-08-10 07:52:21 +00:00
*/
- Only allow the tdq_idx to increase by one each tick rather than up to the most recently chosen index. This significantly improves nice behavior. This allows a lower priority thread to run some multiple of times before the higher priority thread makes it to the front of the queue. A nice +20 cpu hog now only gets ~5% of the cpu when running with a nice 0 cpu hog and about 1.5% with a nice -20 hog. A nice difference of 1 makes a 4% difference in cpu usage between two hogs. - Track a seperate insert and removal index. When the removal index is empty it is updated to point at the current insert index. - Don't remove and re-add a thread to the runq when it is being adjusted down in priority. - Pull some conditional code out of sched_tick(). It's looking a bit large now.
2007-01-04 12:16:19 +00:00
if (tdq->tdq_idx == tdq->tdq_ridx) {
tdq->tdq_idx = (tdq->tdq_idx + 1) % RQ_NQS;
if (TAILQ_EMPTY(&tdq->tdq_timeshare.rq_queues[tdq->tdq_ridx]))
tdq->tdq_ridx = tdq->tdq_idx;
}
Get rid of struct proc p_sched and struct thread td_sched pointers. p_sched is unused. The struct td_sched is always co-allocated with the struct thread, except for the thread0. Avoid useless indirection, instead calculate td_sched location using simple pointer arithmetic in td_get_sched(9). For thread0, which is statically allocated, create a structure to emulate layout of the dynamic allocation. Reviewed by: jhb (previous version) Sponsored by: The FreeBSD Foundation Differential revision: https://reviews.freebsd.org/D6711
2016-06-05 17:04:03 +00:00
ts = td_get_sched(td);
Rewrite thread CPU usage percentage math to not depend on periodic calls with HZ rate through the sched_tick() calls from hardclock(). Potentially it can be used to improve precision, but now it is just minus one more reason to call hardclock() for every HZ tick on every active CPU. SCHED_4BSD never used sched_tick(), but keep it in place for now, as at least SCHED_FBFS existing in patches out of the tree depends on it. MFC after: 1 month
2012-03-13 08:18:54 +00:00
sched_pctcpu_update(ts, 1);
- Restore timeslicing code for all bit SCHED_FIFO priority classes. Reported by: Peter Jeremy <peterjeremy@optushome.com.au>
2008-01-05 04:47:31 +00:00
if (td->td_pri_class & PRI_FIFO_BIT)
- Use a better algorithm in sched_pctcpu_update() Contributed by: Thomaswuerfl@gmx.de - In sched_prio(), adjust the run queue for threads which may need to move to the current queue due to priority propagation . - In sched_switch(), fix style bug introduced when the KSE support went in. Columns are 80 chars wide, not 90. - In sched_switch(), Fix the comparison in the idle case and explicitly re-initialize the runq in the not propagated case. - Remove dead code in sched_clock(). - In sched_clock(), If we're an IDLE class td set NEEDRESCHED so that threads that have become runnable will get a chance to. - In sched_runnable(), if we're not the IDLETD, we should not consider curthread when examining the load. This mimics the 4BSD behavior of returning 0 when the only runnable thread is running. - In sched_userret(), remove the code for setting NEEDRESCHED entirely. This is not necessary and is not implemented in 4BSD. - Use the correct comparison in sched_add() when checking to see if an idle prio task has had it's priority temporarily elevated.
2003-10-27 06:47:05 +00:00
return;
Always use PRI_BASE() when checking the base type of a thread's priority class. MFC after: 2 weeks
2011-01-11 22:13:19 +00:00
if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE) {
- Restore timeslicing code for all bit SCHED_FIFO priority classes. Reported by: Peter Jeremy <peterjeremy@optushome.com.au>
2008-01-05 04:47:31 +00:00
/*
* We used a tick; charge it to the thread so
* that we can compute our interactivity.
*/
Get rid of struct proc p_sched and struct thread td_sched pointers. p_sched is unused. The struct td_sched is always co-allocated with the struct thread, except for the thread0. Avoid useless indirection, instead calculate td_sched location using simple pointer arithmetic in td_get_sched(9). For thread0, which is statically allocated, create a structure to emulate layout of the dynamic allocation. Reviewed by: jhb (previous version) Sponsored by: The FreeBSD Foundation Differential revision: https://reviews.freebsd.org/D6711
2016-06-05 17:04:03 +00:00
td_get_sched(td)->ts_runtime += tickincr;
- Restore timeslicing code for all bit SCHED_FIFO priority classes. Reported by: Peter Jeremy <peterjeremy@optushome.com.au>
2008-01-05 04:47:31 +00:00
sched_interact_update(td);
Reduce ULE context switch time by over 25%. - Only calculate timeshare priorities once per tick or when a thread is woken from sleeping. - Keep the ts_runq pointer valid after all priority changes. - Call tdq_runq_add() directly from sched_switch() without passing in via tdq_add(). We don't need to adjust loads or runqs anymore. - Sort tdq and ts_sched according to utilization to improve cache behavior. Sponsored by: Nokia
2008-03-10 03:15:19 +00:00
sched_priority(td);
- Restore timeslicing code for all bit SCHED_FIFO priority classes. Reported by: Peter Jeremy <peterjeremy@optushome.com.au>
2008-01-05 04:47:31 +00:00
}
Some minor tunings/cleanups inspired by bde@ after previous commits: - remove extra dynamic variable initializations; - restore (4BSD) and implement (ULE) hogticks variable setting; - make sched_rr_interval() more tolerant to options; - restore (4BSD) and implement (ULE) kern.sched.quantum sysctl, a more user-friendly wrapper for sched_slice; - tune some sysctl descriptions; - make some style fixes.
2012-08-10 19:02:49 +00:00
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
/*
Some minor tunings/cleanups inspired by bde@ after previous commits: - remove extra dynamic variable initializations; - restore (4BSD) and implement (ULE) hogticks variable setting; - make sched_rr_interval() more tolerant to options; - restore (4BSD) and implement (ULE) kern.sched.quantum sysctl, a more user-friendly wrapper for sched_slice; - tune some sysctl descriptions; - make some style fixes.
2012-08-10 19:02:49 +00:00
* Force a context switch if the current thread has used up a full
* time slice (default is 100ms).
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
*/
- Change ULE to use dynamic slice sizes for the timeshare queue in order to further reduce latency for threads in this queue. This should help as threads transition from realtime to timeshare. The latency is bound to a max of sched_slice until we have more than sched_slice / 6 threads runnable. Then the min slice is allotted to all threads and latency becomes (nthreads - 1) * min_slice. Discussed with: mav
2012-11-08 01:46:47 +00:00
if (!TD_IS_IDLETHREAD(td) && ++ts->ts_slice >= tdq_slice(tdq)) {
ts->ts_slice = 0;
Some minor tunings/cleanups inspired by bde@ after previous commits: - remove extra dynamic variable initializations; - restore (4BSD) and implement (ULE) hogticks variable setting; - make sched_rr_interval() more tolerant to options; - restore (4BSD) and implement (ULE) kern.sched.quantum sysctl, a more user-friendly wrapper for sched_slice; - tune some sysctl descriptions; - make some style fixes.
2012-08-10 19:02:49 +00:00
td->td_flags |= TDF_NEEDRESCHED | TDF_SLICEEND;
}
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
}
The struct thread td_estcpu member is only used by the 4BSD scheduler. Move it to the struct td_sched for 4BSD, removing always present field, otherwise unused for ULE. New scheduler method sched_estcpu() returns the estimation for kinfo_proc consumption. As before, it always returns 0 for ULE. Remove sched_tick() scheduler method, unused both by 4BSD and ULE. Update locking comment for the 4BSD struct td_sched, copying it from the same comment for ULE. Spell MAXPRI as PRI_MAX_TIMESHARE in the 4BSD comment. Based on some notes from, and reviewed by: bde Sponsored by: The FreeBSD Foundation
2016-04-17 11:04:27 +00:00
u_int
sched_estcpu(struct thread *td __unused)
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
{
The struct thread td_estcpu member is only used by the 4BSD scheduler. Move it to the struct td_sched for 4BSD, removing always present field, otherwise unused for ULE. New scheduler method sched_estcpu() returns the estimation for kinfo_proc consumption. As before, it always returns 0 for ULE. Remove sched_tick() scheduler method, unused both by 4BSD and ULE. Update locking comment for the 4BSD struct td_sched, copying it from the same comment for ULE. Spell MAXPRI as PRI_MAX_TIMESHARE in the 4BSD comment. Based on some notes from, and reviewed by: bde Sponsored by: The FreeBSD Foundation
2016-04-17 11:04:27 +00:00
return (0);
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
}
/*
* Return whether the current CPU has runnable tasks. Used for in-kernel
* cooperative idle threads.
*/
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
int
sched_runnable(void)
{
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
struct tdq *tdq;
- When a new thread is added to a kseq the load is incremented prior to adding it to the nice tables. Therefore, in kseq_add_nice, we should keep in mind that the load will be 1 if we are the only thread, and not 0. - Assert that the sched lock is held in all the appropriate places. - Increase the scope of the sched lock in sched_pctcpu_update(). - Hold the sched lock in sched_runnable(). It is not held by the caller.
2003-06-08 00:47:33 +00:00
int load;
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
- When a new thread is added to a kseq the load is incremented prior to adding it to the nice tables. Therefore, in kseq_add_nice, we should keep in mind that the load will be 1 if we are the only thread, and not 0. - Assert that the sched lock is held in all the appropriate places. - Increase the scope of the sched lock in sched_pctcpu_update(). - Hold the sched lock in sched_runnable(). It is not held by the caller.
2003-06-08 00:47:33 +00:00
load = 1;
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
tdq = TDQ_SELF();
- Use a better algorithm in sched_pctcpu_update() Contributed by: Thomaswuerfl@gmx.de - In sched_prio(), adjust the run queue for threads which may need to move to the current queue due to priority propagation . - In sched_switch(), fix style bug introduced when the KSE support went in. Columns are 80 chars wide, not 90. - In sched_switch(), Fix the comparison in the idle case and explicitly re-initialize the runq in the not propagated case. - Remove dead code in sched_clock(). - In sched_clock(), If we're an IDLE class td set NEEDRESCHED so that threads that have become runnable will get a chance to. - In sched_runnable(), if we're not the IDLETD, we should not consider curthread when examining the load. This mimics the 4BSD behavior of returning 0 when the only runnable thread is running. - In sched_userret(), remove the code for setting NEEDRESCHED entirely. This is not necessary and is not implemented in 4BSD. - Use the correct comparison in sched_add() when checking to see if an idle prio task has had it's priority temporarily elevated.
2003-10-27 06:47:05 +00:00
if ((curthread->td_flags & TDF_IDLETD) != 0) {
- Clean up a bit after the most recent KSE restructuring.
2006-12-29 10:37:07 +00:00
if (tdq->tdq_load > 0)
- Use a better algorithm in sched_pctcpu_update() Contributed by: Thomaswuerfl@gmx.de - In sched_prio(), adjust the run queue for threads which may need to move to the current queue due to priority propagation . - In sched_switch(), fix style bug introduced when the KSE support went in. Columns are 80 chars wide, not 90. - In sched_switch(), Fix the comparison in the idle case and explicitly re-initialize the runq in the not propagated case. - Remove dead code in sched_clock(). - In sched_clock(), If we're an IDLE class td set NEEDRESCHED so that threads that have become runnable will get a chance to. - In sched_runnable(), if we're not the IDLETD, we should not consider curthread when examining the load. This mimics the 4BSD behavior of returning 0 when the only runnable thread is running. - In sched_userret(), remove the code for setting NEEDRESCHED entirely. This is not necessary and is not implemented in 4BSD. - Use the correct comparison in sched_add() when checking to see if an idle prio task has had it's priority temporarily elevated.
2003-10-27 06:47:05 +00:00
goto out;
} else
- Clean up a bit after the most recent KSE restructuring.
2006-12-29 10:37:07 +00:00
if (tdq->tdq_load - 1 > 0)
- Use a better algorithm in sched_pctcpu_update() Contributed by: Thomaswuerfl@gmx.de - In sched_prio(), adjust the run queue for threads which may need to move to the current queue due to priority propagation . - In sched_switch(), fix style bug introduced when the KSE support went in. Columns are 80 chars wide, not 90. - In sched_switch(), Fix the comparison in the idle case and explicitly re-initialize the runq in the not propagated case. - Remove dead code in sched_clock(). - In sched_clock(), If we're an IDLE class td set NEEDRESCHED so that threads that have become runnable will get a chance to. - In sched_runnable(), if we're not the IDLETD, we should not consider curthread when examining the load. This mimics the 4BSD behavior of returning 0 when the only runnable thread is running. - In sched_userret(), remove the code for setting NEEDRESCHED entirely. This is not necessary and is not implemented in 4BSD. - Use the correct comparison in sched_add() when checking to see if an idle prio task has had it's priority temporarily elevated.
2003-10-27 06:47:05 +00:00
goto out;
- When a new thread is added to a kseq the load is incremented prior to adding it to the nice tables. Therefore, in kseq_add_nice, we should keep in mind that the load will be 1 if we are the only thread, and not 0. - Assert that the sched lock is held in all the appropriate places. - Increase the scope of the sched lock in sched_pctcpu_update(). - Hold the sched lock in sched_runnable(). It is not held by the caller.
2003-06-08 00:47:33 +00:00
load = 0;
out:
return (load);
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
}
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* Choose the highest priority thread to run. The thread is removed from
* the run-queue while running however the load remains. For SMP we set
* the tdq in the global idle bitmask if it idles here.
*/
- Catch up to setrunqueue/choosethread/etc. api changes. - Define our own maybe_preempt() as sched_preempt(). We want to be able to preempt idlethread in all cases. - Define our idlethread to require preemption to exit. - Get the cpu estimation tick from sched_tick() so we don't have to worry about errors from a sampling interval that differs from the time domain. This was the source of sched_priority prints/panics and inaccurate pctcpu display in top.
2007-01-23 08:50:34 +00:00
struct thread *
- Fix the ksq_load calculation. It now reflects the number of entries on the run queue for each cpu. - Introduce kse stealing into the sched_choose() code. This helps balance cpus better in cases where process turnover is high. This implementation is fairly trivial and will likely be only a temporary measure until something more sophisticated has been written.
2003-01-28 09:28:20 +00:00
sched_choose(void)
{
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
struct thread *td;
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
struct tdq *tdq;
- Fix the ksq_load calculation. It now reflects the number of entries on the run queue for each cpu. - Introduce kse stealing into the sched_choose() code. This helps balance cpus better in cases where process turnover is high. This implementation is fairly trivial and will likely be only a temporary measure until something more sophisticated has been written.
2003-01-28 09:28:20 +00:00
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
tdq = TDQ_SELF();
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
td = tdq_choose(tdq);
if (td) {
tdq_runq_rem(tdq, td);
- Allow static_boost to specify no boost with '0', traditional kernel fixed pri boost with '1' or any priority less than the current thread's priority with a value greater than two. Default the boost to PRI_MIN_TIMESHARE to prevent regular user-space threads from starving threads in the kernel. This prevents these user-threads from also being scheduled as if they are high fixed-priority kernel threads. - Restore the setting of lowpri in tdq_choose(). It has to be either here or in sched_switch(). I accidentally removed it from both places. Tested by: kris
2008-04-04 01:16:18 +00:00
tdq->tdq_lowpri = td->td_priority;
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
return (td);
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
}
- Allow static_boost to specify no boost with '0', traditional kernel fixed pri boost with '1' or any priority less than the current thread's priority with a value greater than two. Default the boost to PRI_MIN_TIMESHARE to prevent regular user-space threads from starving threads in the kernel. This prevents these user-threads from also being scheduled as if they are high fixed-priority kernel threads. - Restore the setting of lowpri in tdq_choose(). It has to be either here or in sched_switch(). I accidentally removed it from both places. Tested by: kris
2008-04-04 01:16:18 +00:00
tdq->tdq_lowpri = PRI_MAX_IDLE;
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
return (PCPU_GET(idlethread));
- Catch up to setrunqueue/choosethread/etc. api changes. - Define our own maybe_preempt() as sched_preempt(). We want to be able to preempt idlethread in all cases. - Define our idlethread to require preemption to exit. - Get the cpu estimation tick from sched_tick() so we don't have to worry about errors from a sampling interval that differs from the time domain. This was the source of sched_priority prints/panics and inaccurate pctcpu display in top.
2007-01-23 08:50:34 +00:00
}
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* Set owepreempt if necessary. Preemption never happens directly in ULE,
* we always request it once we exit a critical section.
*/
static inline void
sched_setpreempt(struct thread *td)
- Catch up to setrunqueue/choosethread/etc. api changes. - Define our own maybe_preempt() as sched_preempt(). We want to be able to preempt idlethread in all cases. - Define our idlethread to require preemption to exit. - Get the cpu estimation tick from sched_tick() so we don't have to worry about errors from a sampling interval that differs from the time domain. This was the source of sched_priority prints/panics and inaccurate pctcpu display in top.
2007-01-23 08:50:34 +00:00
{
struct thread *ctd;
int cpri;
int pri;
- Add an implementation of sched_preempt() that avoids excessive IPIs. - Normalize the preemption/ipi setting code by introducing sched_shouldpreempt() so the logical is identical and not repeated between tdq_notify() and sched_setpreempt(). - In tdq_notify() don't set NEEDRESCHED as we may not actually own the thread lock this could have caused us to lose td_flags settings. - Garbage collect some tunables that are no longer relevant.
2008-03-10 01:32:01 +00:00
THREAD_LOCK_ASSERT(curthread, MA_OWNED);
- Catch up to setrunqueue/choosethread/etc. api changes. - Define our own maybe_preempt() as sched_preempt(). We want to be able to preempt idlethread in all cases. - Define our idlethread to require preemption to exit. - Get the cpu estimation tick from sched_tick() so we don't have to worry about errors from a sampling interval that differs from the time domain. This was the source of sched_priority prints/panics and inaccurate pctcpu display in top.
2007-01-23 08:50:34 +00:00
ctd = curthread;
pri = td->td_priority;
cpri = ctd->td_priority;
- Add an implementation of sched_preempt() that avoids excessive IPIs. - Normalize the preemption/ipi setting code by introducing sched_shouldpreempt() so the logical is identical and not repeated between tdq_notify() and sched_setpreempt(). - In tdq_notify() don't set NEEDRESCHED as we may not actually own the thread lock this could have caused us to lose td_flags settings. - Garbage collect some tunables that are no longer relevant.
2008-03-10 01:32:01 +00:00
if (pri < cpri)
ctd->td_flags |= TDF_NEEDRESCHED;
- Catch up to setrunqueue/choosethread/etc. api changes. - Define our own maybe_preempt() as sched_preempt(). We want to be able to preempt idlethread in all cases. - Define our idlethread to require preemption to exit. - Get the cpu estimation tick from sched_tick() so we don't have to worry about errors from a sampling interval that differs from the time domain. This was the source of sched_priority prints/panics and inaccurate pctcpu display in top.
2007-01-23 08:50:34 +00:00
if (panicstr != NULL || pri >= cpri || cold || TD_IS_INHIBITED(ctd))
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
return;
- Add an implementation of sched_preempt() that avoids excessive IPIs. - Normalize the preemption/ipi setting code by introducing sched_shouldpreempt() so the logical is identical and not repeated between tdq_notify() and sched_setpreempt(). - In tdq_notify() don't set NEEDRESCHED as we may not actually own the thread lock this could have caused us to lose td_flags settings. - Garbage collect some tunables that are no longer relevant.
2008-03-10 01:32:01 +00:00
if (!sched_shouldpreempt(pri, cpri, 0))
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
return;
ctd->td_owepreempt = 1;
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
}
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
Reduce ULE context switch time by over 25%. - Only calculate timeshare priorities once per tick or when a thread is woken from sleeping. - Keep the ts_runq pointer valid after all priority changes. - Call tdq_runq_add() directly from sched_switch() without passing in via tdq_add(). We don't need to adjust loads or runqs anymore. - Sort tdq and ts_sched according to utilization to improve cache behavior. Sponsored by: Nokia
2008-03-10 03:15:19 +00:00
* Add a thread to a thread queue. Select the appropriate runq and add the
* thread to it. This is the internal function called when the tdq is
* predetermined.
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
*/
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
void
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
tdq_add(struct tdq *tdq, struct thread *td, int flags)
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
{
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
- Catch up to setrunqueue/choosethread/etc. api changes. - Define our own maybe_preempt() as sched_preempt(). We want to be able to preempt idlethread in all cases. - Define our idlethread to require preemption to exit. - Get the cpu estimation tick from sched_tick() so we don't have to worry about errors from a sampling interval that differs from the time domain. This was the source of sched_priority prints/panics and inaccurate pctcpu display in top.
2007-01-23 08:50:34 +00:00
KASSERT((td->td_inhibitors == 0),
("sched_add: trying to run inhibited thread"));
KASSERT((TD_CAN_RUN(td) || TD_IS_RUNNING(td)),
("sched_add: bad thread state"));
- Move all of the PS_ flags into either p_flag or td_flags. - p_sflag was mostly protected by PROC_LOCK rather than the PROC_SLOCK or previously the sched_lock. These bugs have existed for some time. - Allow swapout to try each thread in a process individually and then swapin the whole process if any of these fail. This allows us to move most scheduler related swap flags into td_flags. - Keep ki_sflag for backwards compat but change all in source tools to use the new and more correct location of P_INMEM. Reported by: pho Reviewed by: attilio, kib Approved by: re (kensmith)
2007-09-17 05:31:39 +00:00
KASSERT(td->td_flags & TDF_INMEM,
("sched_add: thread swapped out"));
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
if (td->td_priority < tdq->tdq_lowpri)
tdq->tdq_lowpri = td->td_priority;
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
tdq_runq_add(tdq, td, flags);
tdq_load_add(tdq, td);
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
}
/*
* Select the target thread queue and add a thread to it. Request
* preemption or IPI a remote processor if required.
*/
void
sched_add(struct thread *td, int flags)
{
struct tdq *tdq;
Major revamp of ULE's cpu load balancing: - Switch back to direct modification of remote CPU run queues. This added a lot of complexity with questionable gain. It's easy enough to reimplement if it's shown to help on huge machines. - Re-implement the old tdq_transfer() call as tdq_pickidle(). Change sched_add() so we have selectable cpu choosers and simplify the logic a bit here. - Implement tdq_pickpri() as the new default cpu chooser. This algorithm is similar to Solaris in that it tries to always run the threads with the best priorities. It is actually slightly more complex than solaris's algorithm because we also tend to favor the local cpu over other cpus which has a boost in latency but also potentially enables cache sharing between the waking thread and the woken thread. - Add a bunch of tunables that can be used to measure effects of different load balancing strategies. Most of these will go away once the algorithm is more definite. - Add a new mechanism to steal threads from busy cpus when we idle. This is enabled with kern.sched.steal_busy and kern.sched.busy_thresh. The threshold is the required length of a tdq's run queue before another cpu will be able to steal runnable threads. This prevents most queue imbalances that contribute the long latencies.
2007-01-19 21:56:08 +00:00
#ifdef SMP
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
int cpu;
#endif
- Implement generic macros for producing KTR records that are compatible with src/tools/sched/schedgraph.py. This allows developers to quickly create a graphical view of ktr data for any resource in the system. - Add sched_tdname() and the pcpu field 'name' for quickly and uniformly identifying records associated with a thread or cpu. - Reimplement the KTR_SCHED traces using the new generic facility. Obtained from: attilio Discussed with: jhb Sponsored by: Nokia
2009-01-17 07:17:57 +00:00
KTR_STATE2(KTR_SCHED, "thread", sched_tdname(td), "runq add",
"prio:%d", td->td_priority, KTR_ATTR_LINKED,
sched_tdname(curthread));
KTR_POINT1(KTR_SCHED, "thread", sched_tdname(curthread), "wokeup",
KTR_ATTR_LINKED, sched_tdname(td));
Implement the DTrace sched provider. This implementation aims to be compatible with the sched provider implemented by Solaris and its open- source derivatives. Full documentation of the sched provider can be found on Oracle's DTrace wiki pages. Note that for compatibility with scripts originally written for Solaris, serveral probes are defined that will never fire. These probes are defined to fire when Solaris-specific features perform certain actions. As these features are not present in FreeBSD, the probes can never fire. Also, I have added a two probes that are not defined in Solaris, lend-pri and load-change. These probes have been added to make it possible to collect schedgraph data with DTrace. Finally, a few probes are defined in Solaris to take a cpuinfo_t * argument. As it was not immediately clear to me how to translate that to FreeBSD, currently those probes are passed NULL in place of a cpuinfo_t *. Sponsored by: Sandvine Incorporated MFC after: 2 weeks
2012-05-15 01:30:25 +00:00
SDT_PROBE4(sched, , , enqueue, td, td->td_proc, NULL,
flags & SRQ_PREEMPTED);
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
THREAD_LOCK_ASSERT(td, MA_OWNED);
/*
* Recalculate the priority before we select the target cpu or
* run-queue.
*/
if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE)
sched_priority(td);
#ifdef SMP
/*
* Pick the destination cpu and if it isn't ours transfer to the
* target cpu.
*/
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
cpu = sched_pickcpu(td, flags);
tdq = sched_setcpu(td, cpu, flags);
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
tdq_add(tdq, td, flags);
Reduce ULE context switch time by over 25%. - Only calculate timeshare priorities once per tick or when a thread is woken from sleeping. - Keep the ts_runq pointer valid after all priority changes. - Call tdq_runq_add() directly from sched_switch() without passing in via tdq_add(). We don't need to adjust loads or runqs anymore. - Sort tdq and ts_sched according to utilization to improve cache behavior. Sponsored by: Nokia
2008-03-10 03:15:19 +00:00
if (cpu != PCPU_GET(cpuid)) {
Revert r313814 and r313816 Something evidently got mangled in my git tree in between testing and review, as an old and broken version of the patch was apparently submitted to svn. Revert this while I work out what went wrong. Reported by: tuexen Pointy hat to: rstone
2017-02-16 21:18:31 +00:00
tdq_notify(tdq, td);
Major revamp of ULE's cpu load balancing: - Switch back to direct modification of remote CPU run queues. This added a lot of complexity with questionable gain. It's easy enough to reimplement if it's shown to help on huge machines. - Re-implement the old tdq_transfer() call as tdq_pickidle(). Change sched_add() so we have selectable cpu choosers and simplify the logic a bit here. - Implement tdq_pickpri() as the new default cpu chooser. This algorithm is similar to Solaris in that it tries to always run the threads with the best priorities. It is actually slightly more complex than solaris's algorithm because we also tend to favor the local cpu over other cpus which has a boost in latency but also potentially enables cache sharing between the waking thread and the woken thread. - Add a bunch of tunables that can be used to measure effects of different load balancing strategies. Most of these will go away once the algorithm is more definite. - Add a new mechanism to steal threads from busy cpus when we idle. This is enabled with kern.sched.steal_busy and kern.sched.busy_thresh. The threshold is the required length of a tdq's run queue before another cpu will be able to steal runnable threads. This prevents most queue imbalances that contribute the long latencies.
2007-01-19 21:56:08 +00:00
return;
}
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
#else
tdq = TDQ_SELF();
TDQ_LOCK(tdq);
/*
* Now that the thread is moving to the run-queue, set the lock
* to the scheduler's lock.
*/
thread_lock_set(td, TDQ_LOCKPTR(tdq));
tdq_add(tdq, td, flags);
Major revamp of ULE's cpu load balancing: - Switch back to direct modification of remote CPU run queues. This added a lot of complexity with questionable gain. It's easy enough to reimplement if it's shown to help on huge machines. - Re-implement the old tdq_transfer() call as tdq_pickidle(). Change sched_add() so we have selectable cpu choosers and simplify the logic a bit here. - Implement tdq_pickpri() as the new default cpu chooser. This algorithm is similar to Solaris in that it tries to always run the threads with the best priorities. It is actually slightly more complex than solaris's algorithm because we also tend to favor the local cpu over other cpus which has a boost in latency but also potentially enables cache sharing between the waking thread and the woken thread. - Add a bunch of tunables that can be used to measure effects of different load balancing strategies. Most of these will go away once the algorithm is more definite. - Add a new mechanism to steal threads from busy cpus when we idle. This is enabled with kern.sched.steal_busy and kern.sched.busy_thresh. The threshold is the required length of a tdq's run queue before another cpu will be able to steal runnable threads. This prevents most queue imbalances that contribute the long latencies.
2007-01-19 21:56:08 +00:00
#endif
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
if (!(flags & SRQ_YIELDING))
sched_setpreempt(td);
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
}
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* Remove a thread from a run-queue without running it. This is used
* when we're stealing a thread from a remote queue. Otherwise all threads
* exit by calling sched_exit_thread() and sched_throw() themselves.
*/
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
void
- Update the sched api. sched_{add,rem,clock,pctcpu} now all accept a td argument rather than a kse.
2003-10-16 08:39:15 +00:00
sched_rem(struct thread *td)
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
{
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
struct tdq *tdq;
- Update the sched api. sched_{add,rem,clock,pctcpu} now all accept a td argument rather than a kse.
2003-10-16 08:39:15 +00:00
- Implement generic macros for producing KTR records that are compatible with src/tools/sched/schedgraph.py. This allows developers to quickly create a graphical view of ktr data for any resource in the system. - Add sched_tdname() and the pcpu field 'name' for quickly and uniformly identifying records associated with a thread or cpu. - Reimplement the KTR_SCHED traces using the new generic facility. Obtained from: attilio Discussed with: jhb Sponsored by: Nokia
2009-01-17 07:17:57 +00:00
KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "runq rem",
"prio:%d", td->td_priority);
Implement the DTrace sched provider. This implementation aims to be compatible with the sched provider implemented by Solaris and its open- source derivatives. Full documentation of the sched provider can be found on Oracle's DTrace wiki pages. Note that for compatibility with scripts originally written for Solaris, serveral probes are defined that will never fire. These probes are defined to fire when Solaris-specific features perform certain actions. As these features are not present in FreeBSD, the probes can never fire. Also, I have added a two probes that are not defined in Solaris, lend-pri and load-change. These probes have been added to make it possible to collect schedgraph data with DTrace. Finally, a few probes are defined in Solaris to take a cpuinfo_t * argument. As it was not immediately clear to me how to translate that to FreeBSD, currently those probes are passed NULL in place of a cpuinfo_t *. Sponsored by: Sandvine Incorporated MFC after: 2 weeks
2012-05-15 01:30:25 +00:00
SDT_PROBE3(sched, , , dequeue, td, td->td_proc, NULL);
Get rid of struct proc p_sched and struct thread td_sched pointers. p_sched is unused. The struct td_sched is always co-allocated with the struct thread, except for the thread0. Avoid useless indirection, instead calculate td_sched location using simple pointer arithmetic in td_get_sched(9). For thread0, which is statically allocated, create a structure to emulate layout of the dynamic allocation. Reviewed by: jhb (previous version) Sponsored by: The FreeBSD Foundation Differential revision: https://reviews.freebsd.org/D6711
2016-06-05 17:04:03 +00:00
tdq = TDQ_CPU(td_get_sched(td)->ts_cpu);
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
- Catch up to setrunqueue/choosethread/etc. api changes. - Define our own maybe_preempt() as sched_preempt(). We want to be able to preempt idlethread in all cases. - Define our idlethread to require preemption to exit. - Get the cpu estimation tick from sched_tick() so we don't have to worry about errors from a sampling interval that differs from the time domain. This was the source of sched_priority prints/panics and inaccurate pctcpu display in top.
2007-01-23 08:50:34 +00:00
KASSERT(TD_ON_RUNQ(td),
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
("sched_rem: thread not on run queue"));
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
tdq_runq_rem(tdq, td);
tdq_load_rem(tdq, td);
- Catch up to setrunqueue/choosethread/etc. api changes. - Define our own maybe_preempt() as sched_preempt(). We want to be able to preempt idlethread in all cases. - Define our idlethread to require preemption to exit. - Get the cpu estimation tick from sched_tick() so we don't have to worry about errors from a sampling interval that differs from the time domain. This was the source of sched_priority prints/panics and inaccurate pctcpu display in top.
2007-01-23 08:50:34 +00:00
TD_SET_CAN_RUN(td);
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
if (td->td_priority == tdq->tdq_lowpri)
tdq_setlowpri(tdq, NULL);
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
}
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* Fetch cpu utilization information. Updates on demand.
*/
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
fixpt_t
- Update the sched api. sched_{add,rem,clock,pctcpu} now all accept a td argument rather than a kse.
2003-10-16 08:39:15 +00:00
sched_pctcpu(struct thread *td)
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
{
fixpt_t pctcpu;
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
struct td_sched *ts;
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
pctcpu = 0;
Get rid of struct proc p_sched and struct thread td_sched pointers. p_sched is unused. The struct td_sched is always co-allocated with the struct thread, except for the thread0. Avoid useless indirection, instead calculate td_sched location using simple pointer arithmetic in td_get_sched(9). For thread0, which is statically allocated, create a structure to emulate layout of the dynamic allocation. Reviewed by: jhb (previous version) Sponsored by: The FreeBSD Foundation Differential revision: https://reviews.freebsd.org/D6711
2016-06-05 17:04:03 +00:00
ts = td_get_sched(td);
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
Assert that the thread lock is held in sched_pctcpu() instead of recursively acquiring it. All of the current callers already hold the lock. MFC after: 1 month
2010-06-03 16:02:11 +00:00
THREAD_LOCK_ASSERT(td, MA_OWNED);
Rewrite thread CPU usage percentage math to not depend on periodic calls with HZ rate through the sched_tick() calls from hardclock(). Potentially it can be used to improve precision, but now it is just minus one more reason to call hardclock() for every HZ tick on every active CPU. SCHED_4BSD never used sched_tick(), but keep it in place for now, as at least SCHED_FBFS existing in patches out of the tree depends on it. MFC after: 1 month
2012-03-13 08:18:54 +00:00
sched_pctcpu_update(ts, TD_IS_RUNNING(td));
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
if (ts->ts_ticks) {
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
int rtick;
/* How many rtick per second ? */
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
rtick = min(SCHED_TICK_HZ(ts) / SCHED_TICK_SECS, hz);
pctcpu = (FSCALE * ((FSCALE * rtick)/hz)) >> FSHIFT;
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
}
return (pctcpu);
}
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
/*
* Enforce affinity settings for a thread. Called after adjustments to
* cpumask.
*/
- Add a new sched_affinity() api to be used in the upcoming cpuset implementation. - Add empty implementations of sched_affinity() to 4BSD and ULE. Sponsored by: Nokia
2008-03-02 07:19:35 +00:00
void
sched_affinity(struct thread *td)
{
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
#ifdef SMP
struct td_sched *ts;
THREAD_LOCK_ASSERT(td, MA_OWNED);
Get rid of struct proc p_sched and struct thread td_sched pointers. p_sched is unused. The struct td_sched is always co-allocated with the struct thread, except for the thread0. Avoid useless indirection, instead calculate td_sched location using simple pointer arithmetic in td_get_sched(9). For thread0, which is statically allocated, create a structure to emulate layout of the dynamic allocation. Reviewed by: jhb (previous version) Sponsored by: The FreeBSD Foundation Differential revision: https://reviews.freebsd.org/D6711
2016-06-05 17:04:03 +00:00
ts = td_get_sched(td);
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
if (THREAD_CAN_SCHED(td, ts->ts_cpu))
return;
- Fix an error that occurs when mp_ncpu is an odd number. steal_thresh is calculated as 0 which causes errors elsewhere. Submitted by: KOIE Hidetaka <koie@suri.co.jp> - When sched_affinity() is called with a thread that is not curthread we need to handle the ON_RUNQ() case by adding the thread to the correct run queue. Submitted by: Justin Teller <justin.teller@gmail.com> MFC after: 1 Week
2009-03-14 11:41:36 +00:00
if (TD_ON_RUNQ(td)) {
sched_rem(td);
sched_add(td, SRQ_BORING);
return;
}
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
if (!TD_IS_RUNNING(td))
return;
/*
Fix a bug with sched_affinity() where it checks td_pinned of another thread in a racy manner, which can lead to attempting to migrate a thread that is pinned to a CPU. Instead, have sched_switch() determine which CPU a thread should run on if the current one is not allowed. KASSERT in sched_bind() that the thread is not yet pinned to a CPU. KASSERT in sched_switch() that only migratable threads or those moving due to a sched_bind() are changing CPUs. sched_affinity code came from jhb@. MFC after: 2 weeks
2010-09-01 20:32:47 +00:00
* Force a switch before returning to userspace. If the
* target thread is not running locally send an ipi to force
* the issue.
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
*/
Comment nit, set TDF_NEEDRESCHED after the comment describing why it is done rather than before. MFC after: 1 week
2010-09-21 19:12:22 +00:00
td->td_flags |= TDF_NEEDRESCHED;
Fix a bug with sched_affinity() where it checks td_pinned of another thread in a racy manner, which can lead to attempting to migrate a thread that is pinned to a CPU. Instead, have sched_switch() determine which CPU a thread should run on if the current one is not allowed. KASSERT in sched_bind() that the thread is not yet pinned to a CPU. KASSERT in sched_switch() that only migratable threads or those moving due to a sched_bind() are changing CPUs. sched_affinity code came from jhb@. MFC after: 2 weeks
2010-09-01 20:32:47 +00:00
if (td != curthread)
ipi_cpu(ts->ts_cpu, IPI_PREEMPT);
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
#endif
- Add a new sched_affinity() api to be used in the upcoming cpuset implementation. - Add empty implementations of sched_affinity() to 4BSD and ULE. Sponsored by: Nokia
2008-03-02 07:19:35 +00:00
}
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* Bind a thread to a target cpu.
*/
- Add initial support for pinning and binding.
2003-11-04 07:45:41 +00:00
void
sched_bind(struct thread *td, int cpu)
{
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
struct td_sched *ts;
- Add initial support for pinning and binding.
2003-11-04 07:45:41 +00:00
- Share scheduler locks between hyper-threaded cores to protect the tdq_group structure. Hyper-threaded cores won't really benefit from seperate locks anyway. - Seperate out the migration case from sched_switch to simplify the main switch code. We only migrate here if called via sched_bind(). - When preempted place the preempted thread back in the same queue at the head. - Improve the cpu group and topology infrastructure. Tested by: many on current@ Approved by: re
2007-08-03 23:38:46 +00:00
THREAD_LOCK_ASSERT(td, MA_OWNED|MA_NOTRECURSED);
Assert that the thread passed to sched_bind() and sched_unbind() is curthread as those routines are only supported for curthread currently. MFC after: 1 month
2010-05-21 17:15:56 +00:00
KASSERT(td == curthread, ("sched_bind: can only bind curthread"));
Get rid of struct proc p_sched and struct thread td_sched pointers. p_sched is unused. The struct td_sched is always co-allocated with the struct thread, except for the thread0. Avoid useless indirection, instead calculate td_sched location using simple pointer arithmetic in td_get_sched(9). For thread0, which is statically allocated, create a structure to emulate layout of the dynamic allocation. Reviewed by: jhb (previous version) Sponsored by: The FreeBSD Foundation Differential revision: https://reviews.freebsd.org/D6711
2016-06-05 17:04:03 +00:00
ts = td_get_sched(td);
- In tdq_transfer() always set NEEDRESCHED when necessary regardless of the ipi settings. If NEEDRESCHED is set and an ipi is later delivered it will clear it rather than cause extra context switches. However, if we miss setting it we can have terrible latency. - In sched_bind() correctly implement bind. Also be slightly more tolerant of code which calls bind multiple times. However, we don't change binding if another call is made with a different cpu. This does not presently work with hwpmc which I believe should be changed.
2007-01-20 09:03:43 +00:00
if (ts->ts_flags & TSF_BOUND)
- We do need to IPI the idlethread on some systems. It may be stuck in a power saving mode otherwise. - If the thread is already bound in sched_bind() unbind it before re-binding it to a new cpu. I don't like these semantics but they are expected by some code in the tree. Patch by jkoshy.
2007-01-20 17:03:33 +00:00
sched_unbind(td);
Fix a bug with sched_affinity() where it checks td_pinned of another thread in a racy manner, which can lead to attempting to migrate a thread that is pinned to a CPU. Instead, have sched_switch() determine which CPU a thread should run on if the current one is not allowed. KASSERT in sched_bind() that the thread is not yet pinned to a CPU. KASSERT in sched_switch() that only migratable threads or those moving due to a sched_bind() are changing CPUs. sched_affinity code came from jhb@. MFC after: 2 weeks
2010-09-01 20:32:47 +00:00
KASSERT(THREAD_CAN_MIGRATE(td), ("%p must be migratable", td));
Threading cleanup.. part 2 of several. Make part of John Birrell's KSE patch permanent.. Specifically, remove: Any reference of the ksegrp structure. This feature was never fully utilised and made things overly complicated. All code in the scheduler that tried to make threaded programs fair to unthreaded programs. Libpthread processes will already do this to some extent and libthr processes already disable it. Also: Since this makes such a big change to the scheduler(s), take the opportunity to rename some structures and elements that had to be moved anyhow. This makes the code a lot more readable. The ULE scheduler compiles again but I have no idea if it works. The 4bsd scheduler still reqires a little cleaning and some functions that now do ALMOST nothing will go away, but I thought I'd do that as a separate commit. Tested by David Xu, and Dan Eischen using libthr and libpthread.
2006-12-06 06:34:57 +00:00
ts->ts_flags |= TSF_BOUND;
- In tdq_transfer() always set NEEDRESCHED when necessary regardless of the ipi settings. If NEEDRESCHED is set and an ipi is later delivered it will clear it rather than cause extra context switches. However, if we miss setting it we can have terrible latency. - In sched_bind() correctly implement bind. Also be slightly more tolerant of code which calls bind multiple times. However, we don't change binding if another call is made with a different cpu. This does not presently work with hwpmc which I believe should be changed.
2007-01-20 09:03:43 +00:00
sched_pin();
- Add support for CPU groups to ule. All SMT cores on the same physical cpu are added to a group. - Don't place a cpu into the kseq_idle bitmask until all cpus in that group have idled. - Prefer idle groups over idle group members in the new kseq_transfer() function. In this way we will prefer to balance load across full cores rather than add further load a partial core. - Before a cpu goes idle, check the other group members for threads. Since SMT cpus may freely share threads, this is cheap. - SMT cores may be individually pinned and bound to now. This contrasts the old mechanism where binding or pinning would have allowed a thread to run on any available cpu. - Remove some unnecessary logic from sched_switch(). Priority propagation should be properly taken care of in sched_prio() now.
2003-12-11 03:57:10 +00:00
if (PCPU_GET(cpuid) == cpu)
- Add initial support for pinning and binding.
2003-11-04 07:45:41 +00:00
return;
- In tdq_transfer() always set NEEDRESCHED when necessary regardless of the ipi settings. If NEEDRESCHED is set and an ipi is later delivered it will clear it rather than cause extra context switches. However, if we miss setting it we can have terrible latency. - In sched_bind() correctly implement bind. Also be slightly more tolerant of code which calls bind multiple times. However, we don't change binding if another call is made with a different cpu. This does not presently work with hwpmc which I believe should be changed.
2007-01-20 09:03:43 +00:00
ts->ts_cpu = cpu;
- Add initial support for pinning and binding.
2003-11-04 07:45:41 +00:00
/* When we return from mi_switch we'll be on the correct cpu. */
Add NULL arg to mi_switch() call to stop kernel compiles from breaking.
2004-07-03 16:57:51 +00:00
mi_switch(SW_VOL, NULL);
- Add initial support for pinning and binding.
2003-11-04 07:45:41 +00:00
}
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* Release a bound thread.
*/
- Add initial support for pinning and binding.
2003-11-04 07:45:41 +00:00
void
sched_unbind(struct thread *td)
{
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
struct td_sched *ts;
Commit 1/14 of sched_lock decomposition. - Move all scheduler locking into the schedulers utilizing a technique similar to solaris's container locking. - A per-process spinlock is now used to protect the queue of threads, thread count, suspension count, p_sflags, and other process related scheduling fields. - The new thread lock is actually a pointer to a spinlock for the container that the thread is currently owned by. The container may be a turnstile, sleepqueue, or run queue. - thread_lock() is now used to protect access to thread related scheduling fields. thread_unlock() unlocks the lock and thread_set_lock() implements the transition from one lock to another. - A new "blocked_lock" is used in cases where it is not safe to hold the actual thread's lock yet we must prevent access to the thread. - sched_throw() and sched_fork_exit() are introduced to allow the schedulers to fix-up locking at these points. - Add some minor infrastructure for optionally exporting scheduler statistics that were invaluable in solving performance problems with this patch. Generally these statistics allow you to differentiate between different causes of context switches. Tested by: kris, current@ Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc. Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:50:30 +00:00
THREAD_LOCK_ASSERT(td, MA_OWNED);
Assert that the thread passed to sched_bind() and sched_unbind() is curthread as those routines are only supported for curthread currently. MFC after: 1 month
2010-05-21 17:15:56 +00:00
KASSERT(td == curthread, ("sched_unbind: can only bind curthread"));
Get rid of struct proc p_sched and struct thread td_sched pointers. p_sched is unused. The struct td_sched is always co-allocated with the struct thread, except for the thread0. Avoid useless indirection, instead calculate td_sched location using simple pointer arithmetic in td_get_sched(9). For thread0, which is statically allocated, create a structure to emulate layout of the dynamic allocation. Reviewed by: jhb (previous version) Sponsored by: The FreeBSD Foundation Differential revision: https://reviews.freebsd.org/D6711
2016-06-05 17:04:03 +00:00
ts = td_get_sched(td);
- In tdq_transfer() always set NEEDRESCHED when necessary regardless of the ipi settings. If NEEDRESCHED is set and an ipi is later delivered it will clear it rather than cause extra context switches. However, if we miss setting it we can have terrible latency. - In sched_bind() correctly implement bind. Also be slightly more tolerant of code which calls bind multiple times. However, we don't change binding if another call is made with a different cpu. This does not presently work with hwpmc which I believe should be changed.
2007-01-20 09:03:43 +00:00
if ((ts->ts_flags & TSF_BOUND) == 0)
return;
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
ts->ts_flags &= ~TSF_BOUND;
sched_unpin();
- Add initial support for pinning and binding.
2003-11-04 07:45:41 +00:00
}
Bring a working snapshot of hwpmc(4), its associated libraries, userland utilities and documentation into -CURRENT. Bump FreeBSD_version. Reviewed by: alc, jhb (kernel changes)
2005-04-19 04:01:25 +00:00
int
sched_is_bound(struct thread *td)
{
Commit 1/14 of sched_lock decomposition. - Move all scheduler locking into the schedulers utilizing a technique similar to solaris's container locking. - A per-process spinlock is now used to protect the queue of threads, thread count, suspension count, p_sflags, and other process related scheduling fields. - The new thread lock is actually a pointer to a spinlock for the container that the thread is currently owned by. The container may be a turnstile, sleepqueue, or run queue. - thread_lock() is now used to protect access to thread related scheduling fields. thread_unlock() unlocks the lock and thread_set_lock() implements the transition from one lock to another. - A new "blocked_lock" is used in cases where it is not safe to hold the actual thread's lock yet we must prevent access to the thread. - sched_throw() and sched_fork_exit() are introduced to allow the schedulers to fix-up locking at these points. - Add some minor infrastructure for optionally exporting scheduler statistics that were invaluable in solving performance problems with this patch. Generally these statistics allow you to differentiate between different causes of context switches. Tested by: kris, current@ Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc. Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:50:30 +00:00
THREAD_LOCK_ASSERT(td, MA_OWNED);
Get rid of struct proc p_sched and struct thread td_sched pointers. p_sched is unused. The struct td_sched is always co-allocated with the struct thread, except for the thread0. Avoid useless indirection, instead calculate td_sched location using simple pointer arithmetic in td_get_sched(9). For thread0, which is statically allocated, create a structure to emulate layout of the dynamic allocation. Reviewed by: jhb (previous version) Sponsored by: The FreeBSD Foundation Differential revision: https://reviews.freebsd.org/D6711
2016-06-05 17:04:03 +00:00
return (td_get_sched(td)->ts_flags & TSF_BOUND);
Bring a working snapshot of hwpmc(4), its associated libraries, userland utilities and documentation into -CURRENT. Bump FreeBSD_version. Reviewed by: alc, jhb (kernel changes)
2005-04-19 04:01:25 +00:00
}
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* Basic yield call.
*/
Add scheduler API sched_relinquish(), the API is used to implement yield() and sched_yield() syscalls. Every scheduler has its own way to relinquish cpu, the ULE and CORE schedulers have two internal run- queues, a timesharing thread which calls yield() syscall should be moved to inactive queue.
2006-06-15 06:37:39 +00:00
void
sched_relinquish(struct thread *td)
{
Commit 1/14 of sched_lock decomposition. - Move all scheduler locking into the schedulers utilizing a technique similar to solaris's container locking. - A per-process spinlock is now used to protect the queue of threads, thread count, suspension count, p_sflags, and other process related scheduling fields. - The new thread lock is actually a pointer to a spinlock for the container that the thread is currently owned by. The container may be a turnstile, sleepqueue, or run queue. - thread_lock() is now used to protect access to thread related scheduling fields. thread_unlock() unlocks the lock and thread_set_lock() implements the transition from one lock to another. - A new "blocked_lock" is used in cases where it is not safe to hold the actual thread's lock yet we must prevent access to the thread. - sched_throw() and sched_fork_exit() are introduced to allow the schedulers to fix-up locking at these points. - Add some minor infrastructure for optionally exporting scheduler statistics that were invaluable in solving performance problems with this patch. Generally these statistics allow you to differentiate between different causes of context switches. Tested by: kris, current@ Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc. Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:50:30 +00:00
thread_lock(td);
- Make SCHED_STATS more generic by adding a wrapper to create the variables and sysctl nodes. - In reset walk the children of kern_sched_stats and reset the counters via the oid_arg1 pointer. This allows us to add arbitrary counters to the tree and still reset them properly. - Define a set of switch types to be passed with flags to mi_switch(). These types are named SWT_*. These types correspond to SCHED_STATS counters and are automatically handled in this way. - Make the new SWT_ types more specific than the older switch stats. There are now stats for idle switches, remote idle wakeups, remote preemption ithreads idling, etc. - Add switch statistics for ULE's pickcpu algorithm. These stats include how much migration there is, how often affinity was successful, how often threads were migrated to the local cpu on wakeup, etc. Sponsored by: Nokia
2008-04-17 04:20:10 +00:00
mi_switch(SW_VOL | SWT_RELINQUISH, NULL);
Commit 1/14 of sched_lock decomposition. - Move all scheduler locking into the schedulers utilizing a technique similar to solaris's container locking. - A per-process spinlock is now used to protect the queue of threads, thread count, suspension count, p_sflags, and other process related scheduling fields. - The new thread lock is actually a pointer to a spinlock for the container that the thread is currently owned by. The container may be a turnstile, sleepqueue, or run queue. - thread_lock() is now used to protect access to thread related scheduling fields. thread_unlock() unlocks the lock and thread_set_lock() implements the transition from one lock to another. - A new "blocked_lock" is used in cases where it is not safe to hold the actual thread's lock yet we must prevent access to the thread. - sched_throw() and sched_fork_exit() are introduced to allow the schedulers to fix-up locking at these points. - Add some minor infrastructure for optionally exporting scheduler statistics that were invaluable in solving performance problems with this patch. Generally these statistics allow you to differentiate between different causes of context switches. Tested by: kris, current@ Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc. Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:50:30 +00:00
thread_unlock(td);
Add scheduler API sched_relinquish(), the API is used to implement yield() and sched_yield() syscalls. Every scheduler has its own way to relinquish cpu, the ULE and CORE schedulers have two internal run- queues, a timesharing thread which calls yield() syscall should be moved to inactive queue.
2006-06-15 06:37:39 +00:00
}
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* Return the total system load.
*/
- Add a new member to struct kseq called ksq_sysload. This is intended to track the load for the sched_load() function. In the SMP case this member is not defined because it would be redundant with the ksg_load member which already tracks the non ithd load. - For sched_load() in the UP case simply return ksq_sysload. In the SMP case traverse the list of kseq groups and sum up their ksg_load fields.
2004-02-01 02:48:36 +00:00
int
sched_load(void)
{
#ifdef SMP
int total;
int i;
total = 0;
Update several places that iterate over CPUs to use CPU_FOREACH().
2010-06-11 18:46:34 +00:00
CPU_FOREACH(i)
Add support for the new cpu topology api: - When searching for affinity search backwards in the tree from the last cpu we ran on while the thread still has affinity for the group. This can take advantage of knowledge of shared L2 or L3 caches among a group of cores. - When searching for the least loaded cpu find the least loaded cpu via the least loaded path through the tree. This load balances system bus links, individual cache levels, and hyper-threaded/SMT cores. - Make the periodic balancer recursively balance the highest and lowest loaded cpu across each link. Add support for cpusets: - Convert the cpuset to a simple native cpumask_t while the kernel still only supports cpumask. - Pass the derived cpumask down through the cpu_search functions to restrict the result cpus. - Make the various steal functions resilient to failure since all threads can not run on all cpus any longer. General improvements: - Precisely track the lowest priority thread on every runq with tdq_setlowpri(). Before it was more advisory but this ended up having pathological behaviors. - Remove many #ifdef SMP conditions to simplify the code. - Get rid of the old cumbersome tdq_group. This is more naturally expressed via the cpu_group tree. Sponsored by: Nokia Testing by: kris
2008-03-02 08:20:59 +00:00
total += TDQ_CPU(i)->tdq_sysload;
- Add a new member to struct kseq called ksq_sysload. This is intended to track the load for the sched_load() function. In the SMP case this member is not defined because it would be redundant with the ksg_load member which already tracks the non ithd load. - For sched_load() in the UP case simply return ksq_sysload. In the SMP case traverse the list of kseq groups and sum up their ksg_load fields.
2004-02-01 02:48:36 +00:00
return (total);
#else
- Clean up a bit after the most recent KSE restructuring.
2006-12-29 10:37:07 +00:00
return (TDQ_SELF()->tdq_sysload);
- Add a new member to struct kseq called ksq_sysload. This is intended to track the load for the sched_load() function. In the SMP case this member is not defined because it would be redundant with the ksg_load member which already tracks the non ithd load. - For sched_load() in the UP case simply return ksq_sysload. In the SMP case traverse the list of kseq groups and sum up their ksg_load fields.
2004-02-01 02:48:36 +00:00
#endif
}
- Add the ule scheduler. This is intended to be a general purpose process scheduler with many SMP benefits. It is still very experimental and should be used only in test environments.
2003-01-26 05:23:15 +00:00
int
sched_sizeof_proc(void)
{
return (sizeof(struct proc));
}
int
sched_sizeof_thread(void)
{
return (sizeof(struct thread) + sizeof(struct td_sched));
}
Add scheduler CORE, the work I have done half a year ago, recent, I picked it up again. The scheduler is forked from ULE, but the algorithm to detect an interactive process is almost completely different with ULE, it comes from Linux paper "Understanding the Linux 2.6.8.1 CPU Scheduler", although I still use same word "score" as a priority boost in ULE scheduler. Briefly, the scheduler has following characteristic: 1. Timesharing process's nice value is seriously respected, timeslice and interaction detecting algorithm are based on nice value. 2. per-cpu scheduling queue and load balancing. 3. O(1) scheduling. 4. Some cpu affinity code in wakeup path. 5. Support POSIX SCHED_FIFO and SCHED_RR. Unlike scheduler 4BSD and ULE which using fuzzy RQ_PPQ, the scheduler uses 256 priority queues. Unlike ULE which using pull and push, the scheduelr uses pull method, the main reason is to let relative idle cpu do the work, but current the whole scheduler is protected by the big sched_lock, so the benefit is not visible, it really can be worse than nothing because all other cpu are locked out when we are doing balancing work, which the 4BSD scheduelr does not have this problem. The scheduler does not support hyperthreading very well, in fact, the scheduler does not make the difference between physical CPU and logical CPU, this should be improved in feature. The scheduler has priority inversion problem on MP machine, it is not good for realtime scheduling, it can cause realtime process starving. As a result, it seems the MySQL super-smack runs better on my Pentium-D machine when using libthr, despite on UP or SMP kernel.
2006-06-13 13:12:56 +00:00
- Fix non-SMP build by encapsulating idle spin logic in a macro. Pointy hat to: me
2009-04-29 23:04:31 +00:00
#ifdef SMP
#define TDQ_IDLESPIN(tdq) \
((tdq)->tdq_cg != NULL && ((tdq)->tdq_cg->cg_flags & CG_FLAG_THREAD) == 0)
#else
#define TDQ_IDLESPIN(tdq) 1
#endif
- Catch up to setrunqueue/choosethread/etc. api changes. - Define our own maybe_preempt() as sched_preempt(). We want to be able to preempt idlethread in all cases. - Define our idlethread to require preemption to exit. - Get the cpu estimation tick from sched_tick() so we don't have to worry about errors from a sampling interval that differs from the time domain. This was the source of sched_priority prints/panics and inaccurate pctcpu display in top.
2007-01-23 08:50:34 +00:00
/*
* The actual idle process.
*/
void
sched_idletd(void *dummy)
{
struct thread *td;
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
struct tdq *tdq;
Several optimizations to sched_idletd(): - Do not try to steal load from other CPUs if there was no contest switches on this CPU (i.e. it was idle all the time and woke up just for bus mastering or TLB shutdown). If current CPU was idle, then it is quite unlikely that some other CPU has load to steal. Under high I/O rate, when TLB shutdowns cause numerous CPU wakeups, on 24-CPU system load stealing code may consume up to 25% of all CPU time without giving any benefits. - Change code that implements spinning for load to restart spin in case of context switch. Previous code periodically called cpu_idle() even under high interrupt/context switch rate. - Rise spinning threshold to 10KHz, where it gives at least some effect that may worth consumed power. Reviewed by: jeff@
2012-11-10 07:02:57 +00:00
int oldswitchcnt, switchcnt;
- Add a metric to describe how busy a processor has been over the last two ticks by counting the number of switches and the load when sched_clock() is called. - If the busy metric exceeds a threshold allow the idle thread to spin waiting for new work for a brief period to avoid using IPIs. This reduces the cost on the sender and receiver as well as reducing wakeup latency considerably when it works. Sponsored by: Nokia
2008-04-17 09:56:01 +00:00
int i;
- Catch up to setrunqueue/choosethread/etc. api changes. - Define our own maybe_preempt() as sched_preempt(). We want to be able to preempt idlethread in all cases. - Define our idlethread to require preemption to exit. - Get the cpu estimation tick from sched_tick() so we don't have to worry about errors from a sampling interval that differs from the time domain. This was the source of sched_priority prints/panics and inaccurate pctcpu display in top.
2007-01-23 08:50:34 +00:00
- Remove the bogus idle thread state code. This may have a race in it and it only optimized out an ipi or mwait in very few cases. - Skip the adaptive idle code when running on SMT or HTT cores. This just wastes cpu time that could be used on a busy thread on the same core. - Rename CG_FLAG_THREAD to CG_FLAG_SMT to be more descriptive. Re-use CG_FLAG_THREAD to mean SMT or HTT. Sponsored by: Nokia
2009-04-29 03:15:43 +00:00
mtx_assert(&Giant, MA_NOTOWNED);
- Catch up to setrunqueue/choosethread/etc. api changes. - Define our own maybe_preempt() as sched_preempt(). We want to be able to preempt idlethread in all cases. - Define our idlethread to require preemption to exit. - Get the cpu estimation tick from sched_tick() so we don't have to worry about errors from a sampling interval that differs from the time domain. This was the source of sched_priority prints/panics and inaccurate pctcpu display in top.
2007-01-23 08:50:34 +00:00
td = curthread;
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
tdq = TDQ_SELF();
Mark the idle threads as non-sleepable and also assert that an idle thread never blocks on a turnstile.
2012-08-22 20:01:38 +00:00
THREAD_NO_SLEEPING();
Several optimizations to sched_idletd(): - Do not try to steal load from other CPUs if there was no contest switches on this CPU (i.e. it was idle all the time and woke up just for bus mastering or TLB shutdown). If current CPU was idle, then it is quite unlikely that some other CPU has load to steal. Under high I/O rate, when TLB shutdowns cause numerous CPU wakeups, on 24-CPU system load stealing code may consume up to 25% of all CPU time without giving any benefits. - Change code that implements spinning for load to restart spin in case of context switch. Previous code periodically called cpu_idle() even under high interrupt/context switch rate. - Rise spinning threshold to 10KHz, where it gives at least some effect that may worth consumed power. Reviewed by: jeff@
2012-11-10 07:02:57 +00:00
oldswitchcnt = -1;
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
for (;;) {
Several optimizations to sched_idletd(): - Do not try to steal load from other CPUs if there was no contest switches on this CPU (i.e. it was idle all the time and woke up just for bus mastering or TLB shutdown). If current CPU was idle, then it is quite unlikely that some other CPU has load to steal. Under high I/O rate, when TLB shutdowns cause numerous CPU wakeups, on 24-CPU system load stealing code may consume up to 25% of all CPU time without giving any benefits. - Change code that implements spinning for load to restart spin in case of context switch. Previous code periodically called cpu_idle() even under high interrupt/context switch rate. - Rise spinning threshold to 10KHz, where it gives at least some effect that may worth consumed power. Reviewed by: jeff@
2012-11-10 07:02:57 +00:00
if (tdq->tdq_load) {
thread_lock(td);
mi_switch(SW_VOL | SWT_IDLE, NULL);
thread_unlock(td);
}
switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
#ifdef SMP
Decrease latency by not wrapping the idle loop's potentially lengthy search for a thread to steal inside a critical section. Since this allows the search to be preempted, restart the search if preemption happens since the search results found earlier may no longer be valid. Decrease the latency of starting a thread that may be assigned to this CPU during the search by polling for incoming threads during the search and switching to that thread instead of continuing the search. Test for stale search results and restart the search before going through the expense of calling tdq_lock_pair(). Retry some tests after grabbing the locks since things may have changed while waiting to get both locks. Eliminate special case handling for stealing from an SMT peer that uses 1 as the steal threshold. This can only succeed if a thread has been assigned but our SMT peer has not yet started executing it. This is quite rare and when it happens the other SMT thread is generally waiting for the same tdq lock that we hold. Basically both SMT threads are racing to grab the same spin lock. Add the kern.sched.always_steal knob from a ULE patch by jeff@. Incorporate another idea from Jeff's ULE patch. If the sched_switch() detects that the CPU is about to go idle, try to steal a thread before switching to the idle thread. Since the search for a thread to steal has to be done inside a critical section in this context, limit the impact on latency by adding the knob kern.sched.trysteal_limit to limit the topological distance of the search and don't restart the search if we detect stale results. If this search can't find an stealable thread, the idle loop can do a more complete search. Also poll for threads being assigned to this CPU during the search and switch to them instead of continuing the search. This change is responsibile for the majority of the improvement in parallel buildworld times. In sched_balance_group() change the minimum threshold from stealing a thread from 1 to 2. Poaching a newly assigned thread from a CPU that is waking up hasn't yet switched to that thread from idle is likely very rare and is likely to have the same lock race as is seen when stealing threads in the idle loop. Also use tdq_notify() to kick the destintation CPU instead of always sending an IPI. Update a stale comment, the number of transferable threads is not calculated. Reviewed by: kib (earlier version) Comments by: avg, jeff, mav MFC after: 1 month Differential Revision: https://reviews.freebsd.org/D12130
2018-02-23 00:12:51 +00:00
if (always_steal || switchcnt != oldswitchcnt) {
Several optimizations to sched_idletd(): - Do not try to steal load from other CPUs if there was no contest switches on this CPU (i.e. it was idle all the time and woke up just for bus mastering or TLB shutdown). If current CPU was idle, then it is quite unlikely that some other CPU has load to steal. Under high I/O rate, when TLB shutdowns cause numerous CPU wakeups, on 24-CPU system load stealing code may consume up to 25% of all CPU time without giving any benefits. - Change code that implements spinning for load to restart spin in case of context switch. Previous code periodically called cpu_idle() even under high interrupt/context switch rate. - Rise spinning threshold to 10KHz, where it gives at least some effect that may worth consumed power. Reviewed by: jeff@
2012-11-10 07:02:57 +00:00
oldswitchcnt = switchcnt;
if (tdq_idled(tdq) == 0)
continue;
}
- Add a metric to describe how busy a processor has been over the last two ticks by counting the number of switches and the load when sched_clock() is called. - If the busy metric exceeds a threshold allow the idle thread to spin waiting for new work for a brief period to avoid using IPIs. This reduces the cost on the sender and receiver as well as reducing wakeup latency considerably when it works. Sponsored by: Nokia
2008-04-17 09:56:01 +00:00
switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
Fix bug in r242852 that prevented CPU from becoming idle if kernel built without SMP support.
2012-11-15 14:10:51 +00:00
#else
oldswitchcnt = switchcnt;
#endif
- Add a metric to describe how busy a processor has been over the last two ticks by counting the number of switches and the load when sched_clock() is called. - If the busy metric exceeds a threshold allow the idle thread to spin waiting for new work for a brief period to avoid using IPIs. This reduces the cost on the sender and receiver as well as reducing wakeup latency considerably when it works. Sponsored by: Nokia
2008-04-17 09:56:01 +00:00
/*
* If we're switching very frequently, spin while checking
* for load rather than entering a low power state that
- Remove the bogus idle thread state code. This may have a race in it and it only optimized out an ipi or mwait in very few cases. - Skip the adaptive idle code when running on SMT or HTT cores. This just wastes cpu time that could be used on a busy thread on the same core. - Rename CG_FLAG_THREAD to CG_FLAG_SMT to be more descriptive. Re-use CG_FLAG_THREAD to mean SMT or HTT. Sponsored by: Nokia
2009-04-29 03:15:43 +00:00
* may require an IPI. However, don't do any busy
* loops while on SMT machines as this simply steals
* cycles from cores doing useful work.
- Add a metric to describe how busy a processor has been over the last two ticks by counting the number of switches and the load when sched_clock() is called. - If the busy metric exceeds a threshold allow the idle thread to spin waiting for new work for a brief period to avoid using IPIs. This reduces the cost on the sender and receiver as well as reducing wakeup latency considerably when it works. Sponsored by: Nokia
2008-04-17 09:56:01 +00:00
*/
- Fix non-SMP build by encapsulating idle spin logic in a macro. Pointy hat to: me
2009-04-29 23:04:31 +00:00
if (TDQ_IDLESPIN(tdq) && switchcnt > sched_idlespinthresh) {
- Add a metric to describe how busy a processor has been over the last two ticks by counting the number of switches and the load when sched_clock() is called. - If the busy metric exceeds a threshold allow the idle thread to spin waiting for new work for a brief period to avoid using IPIs. This reduces the cost on the sender and receiver as well as reducing wakeup latency considerably when it works. Sponsored by: Nokia
2008-04-17 09:56:01 +00:00
for (i = 0; i < sched_idlespins; i++) {
if (tdq->tdq_load)
break;
cpu_spinwait();
}
}
Several optimizations to sched_idletd(): - Do not try to steal load from other CPUs if there was no contest switches on this CPU (i.e. it was idle all the time and woke up just for bus mastering or TLB shutdown). If current CPU was idle, then it is quite unlikely that some other CPU has load to steal. Under high I/O rate, when TLB shutdowns cause numerous CPU wakeups, on 24-CPU system load stealing code may consume up to 25% of all CPU time without giving any benefits. - Change code that implements spinning for load to restart spin in case of context switch. Previous code periodically called cpu_idle() even under high interrupt/context switch rate. - Rise spinning threshold to 10KHz, where it gives at least some effect that may worth consumed power. Reviewed by: jeff@
2012-11-10 07:02:57 +00:00
/* If there was context switch during spin, restart it. */
- Remove the bogus idle thread state code. This may have a race in it and it only optimized out an ipi or mwait in very few cases. - Skip the adaptive idle code when running on SMT or HTT cores. This just wastes cpu time that could be used on a busy thread on the same core. - Rename CG_FLAG_THREAD to CG_FLAG_SMT to be more descriptive. Re-use CG_FLAG_THREAD to mean SMT or HTT. Sponsored by: Nokia
2009-04-29 03:15:43 +00:00
switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
Several optimizations to sched_idletd(): - Do not try to steal load from other CPUs if there was no contest switches on this CPU (i.e. it was idle all the time and woke up just for bus mastering or TLB shutdown). If current CPU was idle, then it is quite unlikely that some other CPU has load to steal. Under high I/O rate, when TLB shutdowns cause numerous CPU wakeups, on 24-CPU system load stealing code may consume up to 25% of all CPU time without giving any benefits. - Change code that implements spinning for load to restart spin in case of context switch. Previous code periodically called cpu_idle() even under high interrupt/context switch rate. - Rise spinning threshold to 10KHz, where it gives at least some effect that may worth consumed power. Reviewed by: jeff@
2012-11-10 07:02:57 +00:00
if (tdq->tdq_load != 0 || switchcnt != oldswitchcnt)
continue;
/* Run main MD idle handler. */
tdq->tdq_cpu_idle = 1;
Add comments describing r271604 change. MFC after: 3 days
2014-09-15 11:17:36 +00:00
/*
* Make sure that tdq_cpu_idle update is globally visible
* before cpu_idle() read tdq_load. The order is important
* to avoid race with tdq_notify.
*/
Change the mb() use in the sched_ult tdq_notify() and sched_idletd() to more C11-ish atomic_thread_fence_seq_cst(). Note that on PowerPC, which currently uses lwsync for mb(), the change actually fixes the missed store/load barrier, intended by r271604 [*]. Reviewed by: alc Noted by: alc [*] Sponsored by: The FreeBSD Foundation MFC after: 3 weeks
2015-07-10 08:54:12 +00:00
atomic_thread_fence_seq_cst();
Decrease latency by not wrapping the idle loop's potentially lengthy search for a thread to steal inside a critical section. Since this allows the search to be preempted, restart the search if preemption happens since the search results found earlier may no longer be valid. Decrease the latency of starting a thread that may be assigned to this CPU during the search by polling for incoming threads during the search and switching to that thread instead of continuing the search. Test for stale search results and restart the search before going through the expense of calling tdq_lock_pair(). Retry some tests after grabbing the locks since things may have changed while waiting to get both locks. Eliminate special case handling for stealing from an SMT peer that uses 1 as the steal threshold. This can only succeed if a thread has been assigned but our SMT peer has not yet started executing it. This is quite rare and when it happens the other SMT thread is generally waiting for the same tdq lock that we hold. Basically both SMT threads are racing to grab the same spin lock. Add the kern.sched.always_steal knob from a ULE patch by jeff@. Incorporate another idea from Jeff's ULE patch. If the sched_switch() detects that the CPU is about to go idle, try to steal a thread before switching to the idle thread. Since the search for a thread to steal has to be done inside a critical section in this context, limit the impact on latency by adding the knob kern.sched.trysteal_limit to limit the topological distance of the search and don't restart the search if we detect stale results. If this search can't find an stealable thread, the idle loop can do a more complete search. Also poll for threads being assigned to this CPU during the search and switch to them instead of continuing the search. This change is responsibile for the majority of the improvement in parallel buildworld times. In sched_balance_group() change the minimum threshold from stealing a thread from 1 to 2. Poaching a newly assigned thread from a CPU that is waking up hasn't yet switched to that thread from idle is likely very rare and is likely to have the same lock race as is seen when stealing threads in the idle loop. Also use tdq_notify() to kick the destintation CPU instead of always sending an IPI. Update a stale comment, the number of transferable threads is not calculated. Reviewed by: kib (earlier version) Comments by: avg, jeff, mav MFC after: 1 month Differential Revision: https://reviews.freebsd.org/D12130
2018-02-23 00:12:51 +00:00
/*
* Checking for again after the fence picks up assigned
* threads often enough to make it worthwhile to do so in
* order to avoid calling cpu_idle().
*/
if (tdq->tdq_load != 0) {
tdq->tdq_cpu_idle = 0;
continue;
}
Several optimizations to sched_idletd(): - Do not try to steal load from other CPUs if there was no contest switches on this CPU (i.e. it was idle all the time and woke up just for bus mastering or TLB shutdown). If current CPU was idle, then it is quite unlikely that some other CPU has load to steal. Under high I/O rate, when TLB shutdowns cause numerous CPU wakeups, on 24-CPU system load stealing code may consume up to 25% of all CPU time without giving any benefits. - Change code that implements spinning for load to restart spin in case of context switch. Previous code periodically called cpu_idle() even under high interrupt/context switch rate. - Rise spinning threshold to 10KHz, where it gives at least some effect that may worth consumed power. Reviewed by: jeff@
2012-11-10 07:02:57 +00:00
cpu_idle(switchcnt * 4 > sched_idlespinthresh);
tdq->tdq_cpu_idle = 0;
/*
* Account thread-less hardware interrupts and
* other wakeup reasons equal to context switches.
*/
switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
if (switchcnt != oldswitchcnt)
continue;
tdq->tdq_switchcnt++;
oldswitchcnt++;
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
}
Add scheduler CORE, the work I have done half a year ago, recent, I picked it up again. The scheduler is forked from ULE, but the algorithm to detect an interactive process is almost completely different with ULE, it comes from Linux paper "Understanding the Linux 2.6.8.1 CPU Scheduler", although I still use same word "score" as a priority boost in ULE scheduler. Briefly, the scheduler has following characteristic: 1. Timesharing process's nice value is seriously respected, timeslice and interaction detecting algorithm are based on nice value. 2. per-cpu scheduling queue and load balancing. 3. O(1) scheduling. 4. Some cpu affinity code in wakeup path. 5. Support POSIX SCHED_FIFO and SCHED_RR. Unlike scheduler 4BSD and ULE which using fuzzy RQ_PPQ, the scheduler uses 256 priority queues. Unlike ULE which using pull and push, the scheduelr uses pull method, the main reason is to let relative idle cpu do the work, but current the whole scheduler is protected by the big sched_lock, so the benefit is not visible, it really can be worse than nothing because all other cpu are locked out when we are doing balancing work, which the 4BSD scheduelr does not have this problem. The scheduler does not support hyperthreading very well, in fact, the scheduler does not make the difference between physical CPU and logical CPU, this should be improved in feature. The scheduler has priority inversion problem on MP machine, it is not good for realtime scheduling, it can cause realtime process starving. As a result, it seems the MySQL super-smack runs better on my Pentium-D machine when using libthr, despite on UP or SMP kernel.
2006-06-13 13:12:56 +00:00
}
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
Commit 1/14 of sched_lock decomposition. - Move all scheduler locking into the schedulers utilizing a technique similar to solaris's container locking. - A per-process spinlock is now used to protect the queue of threads, thread count, suspension count, p_sflags, and other process related scheduling fields. - The new thread lock is actually a pointer to a spinlock for the container that the thread is currently owned by. The container may be a turnstile, sleepqueue, or run queue. - thread_lock() is now used to protect access to thread related scheduling fields. thread_unlock() unlocks the lock and thread_set_lock() implements the transition from one lock to another. - A new "blocked_lock" is used in cases where it is not safe to hold the actual thread's lock yet we must prevent access to the thread. - sched_throw() and sched_fork_exit() are introduced to allow the schedulers to fix-up locking at these points. - Add some minor infrastructure for optionally exporting scheduler statistics that were invaluable in solving performance problems with this patch. Generally these statistics allow you to differentiate between different causes of context switches. Tested by: kris, current@ Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc. Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:50:30 +00:00
/*
* A CPU is entering for the first time or a thread is exiting.
*/
void
sched_throw(struct thread *td)
{
- Reassign the thread queue lock to newtd prior to switching. Assigning after the switch leads to a race where the outgoing thread still owns the local queue lock while another cpu may switch it in. This race is only possible on machines where cpu_switch can take significantly longer on different cpus which in practice means HTT machines with unfair thread scheduling algorithms. Found by: kris (of course) Approved by: re
2007-10-02 01:30:18 +00:00
struct thread *newtd;
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
struct tdq *tdq;
tdq = TDQ_SELF();
Commit 1/14 of sched_lock decomposition. - Move all scheduler locking into the schedulers utilizing a technique similar to solaris's container locking. - A per-process spinlock is now used to protect the queue of threads, thread count, suspension count, p_sflags, and other process related scheduling fields. - The new thread lock is actually a pointer to a spinlock for the container that the thread is currently owned by. The container may be a turnstile, sleepqueue, or run queue. - thread_lock() is now used to protect access to thread related scheduling fields. thread_unlock() unlocks the lock and thread_set_lock() implements the transition from one lock to another. - A new "blocked_lock" is used in cases where it is not safe to hold the actual thread's lock yet we must prevent access to the thread. - sched_throw() and sched_fork_exit() are introduced to allow the schedulers to fix-up locking at these points. - Add some minor infrastructure for optionally exporting scheduler statistics that were invaluable in solving performance problems with this patch. Generally these statistics allow you to differentiate between different causes of context switches. Tested by: kris, current@ Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc. Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:50:30 +00:00
if (td == NULL) {
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/* Correct spinlock nesting and acquire the correct lock. */
TDQ_LOCK(tdq);
Commit 1/14 of sched_lock decomposition. - Move all scheduler locking into the schedulers utilizing a technique similar to solaris's container locking. - A per-process spinlock is now used to protect the queue of threads, thread count, suspension count, p_sflags, and other process related scheduling fields. - The new thread lock is actually a pointer to a spinlock for the container that the thread is currently owned by. The container may be a turnstile, sleepqueue, or run queue. - thread_lock() is now used to protect access to thread related scheduling fields. thread_unlock() unlocks the lock and thread_set_lock() implements the transition from one lock to another. - A new "blocked_lock" is used in cases where it is not safe to hold the actual thread's lock yet we must prevent access to the thread. - sched_throw() and sched_fork_exit() are introduced to allow the schedulers to fix-up locking at these points. - Add some minor infrastructure for optionally exporting scheduler statistics that were invaluable in solving performance problems with this patch. Generally these statistics allow you to differentiate between different causes of context switches. Tested by: kris, current@ Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc. Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:50:30 +00:00
spinlock_exit();
Some small fixes to CPU accounting for threads: - Only initialize the per-cpu switchticks and switchtime in sched_throw() for the very first context switch on APs during boot. This avoids a small gap between the middle of thread_exit() and sched_throw() where time is not accounted to any thread. - In thread_exit(), update the timestamp bookkeeping to track the changes to mi_switch() introduced by td_rux so that the code once again matches the comment claiming it is mimicing mi_switch(). Specifically, only update the per-thread stats directly and depend on ruxagg() to update p_rux rather than adjusting p_rux directly. While here, move the timestamp bookkeeping as late in the function as possible. Reviewed by: bde, kib MFC after: 1 week
2012-01-03 21:03:28 +00:00
PCPU_SET(switchtime, cpu_ticks());
PCPU_SET(switchticks, ticks);
Commit 1/14 of sched_lock decomposition. - Move all scheduler locking into the schedulers utilizing a technique similar to solaris's container locking. - A per-process spinlock is now used to protect the queue of threads, thread count, suspension count, p_sflags, and other process related scheduling fields. - The new thread lock is actually a pointer to a spinlock for the container that the thread is currently owned by. The container may be a turnstile, sleepqueue, or run queue. - thread_lock() is now used to protect access to thread related scheduling fields. thread_unlock() unlocks the lock and thread_set_lock() implements the transition from one lock to another. - A new "blocked_lock" is used in cases where it is not safe to hold the actual thread's lock yet we must prevent access to the thread. - sched_throw() and sched_fork_exit() are introduced to allow the schedulers to fix-up locking at these points. - Add some minor infrastructure for optionally exporting scheduler statistics that were invaluable in solving performance problems with this patch. Generally these statistics allow you to differentiate between different causes of context switches. Tested by: kris, current@ Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc. Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:50:30 +00:00
} else {
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
tdq_load_rem(tdq, td);
- Re-implement lock profiling in such a way that it no longer breaks the ABI when enabled. There is no longer an embedded lock_profile_object in each lock. Instead a list of lock_profile_objects is kept per-thread for each lock it may own. The cnt_hold statistic is now always 0 to facilitate this. - Support shared locking by tracking individual lock instances and statistics in the per-thread per-instance lock_profile_object. - Make the lock profiling hash table a per-cpu singly linked list with a per-cpu static lock_prof allocator. This removes the need for an array of spinlocks and reduces cache contention between cores. - Use a seperate hash for spinlocks and other locks so that only a critical_enter() is required and not a spinlock_enter() to modify the per-cpu tables. - Count time spent spinning in the lock statistics. - Remove the LOCK_PROFILE_SHARED option as it is always supported now. - Specifically drop and release the scheduler locks in both schedulers since we track owners now. In collaboration with: Kip Macy Sponsored by: Nokia
2007-12-15 23:13:31 +00:00
lock_profile_release_lock(&TDQ_LOCKPTR(tdq)->lock_object);
kgdb uses td_oncpu to determine if a thread is running and should use a pcb from stoppcbs[] rather than the thread's PCB. However, exited threads retained td_oncpu from the last time they ran, and newborn threads had their CPU fields cleared to zero during fork and thread creation since they are in the set of fields zeroed when threads are setup. To fix, explicitly update the CPU fields for exiting threads in sched_throw() to reflect the switch out and reset the CPU fields for new threads in sched_fork_thread() to NOCPU. Reviewed by: kib MFC after: 1 week Differential Revision: https://reviews.freebsd.org/D3193
2015-08-03 20:43:36 +00:00
td->td_lastcpu = td->td_oncpu;
td->td_oncpu = NOCPU;
Commit 1/14 of sched_lock decomposition. - Move all scheduler locking into the schedulers utilizing a technique similar to solaris's container locking. - A per-process spinlock is now used to protect the queue of threads, thread count, suspension count, p_sflags, and other process related scheduling fields. - The new thread lock is actually a pointer to a spinlock for the container that the thread is currently owned by. The container may be a turnstile, sleepqueue, or run queue. - thread_lock() is now used to protect access to thread related scheduling fields. thread_unlock() unlocks the lock and thread_set_lock() implements the transition from one lock to another. - A new "blocked_lock" is used in cases where it is not safe to hold the actual thread's lock yet we must prevent access to the thread. - sched_throw() and sched_fork_exit() are introduced to allow the schedulers to fix-up locking at these points. - Add some minor infrastructure for optionally exporting scheduler statistics that were invaluable in solving performance problems with this patch. Generally these statistics allow you to differentiate between different causes of context switches. Tested by: kris, current@ Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc. Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:50:30 +00:00
}
KASSERT(curthread->td_md.md_spinlock_count == 1, ("invalid count"));
- Reassign the thread queue lock to newtd prior to switching. Assigning after the switch leads to a race where the outgoing thread still owns the local queue lock while another cpu may switch it in. This race is only possible on machines where cpu_switch can take significantly longer on different cpus which in practice means HTT machines with unfair thread scheduling algorithms. Found by: kris (of course) Approved by: re
2007-10-02 01:30:18 +00:00
newtd = choosethread();
TDQ_LOCKPTR(tdq)->mtx_lock = (uintptr_t)newtd;
cpu_throw(td, newtd); /* doesn't return */
Commit 1/14 of sched_lock decomposition. - Move all scheduler locking into the schedulers utilizing a technique similar to solaris's container locking. - A per-process spinlock is now used to protect the queue of threads, thread count, suspension count, p_sflags, and other process related scheduling fields. - The new thread lock is actually a pointer to a spinlock for the container that the thread is currently owned by. The container may be a turnstile, sleepqueue, or run queue. - thread_lock() is now used to protect access to thread related scheduling fields. thread_unlock() unlocks the lock and thread_set_lock() implements the transition from one lock to another. - A new "blocked_lock" is used in cases where it is not safe to hold the actual thread's lock yet we must prevent access to the thread. - sched_throw() and sched_fork_exit() are introduced to allow the schedulers to fix-up locking at these points. - Add some minor infrastructure for optionally exporting scheduler statistics that were invaluable in solving performance problems with this patch. Generally these statistics allow you to differentiate between different causes of context switches. Tested by: kris, current@ Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc. Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:50:30 +00:00
}
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
/*
* This is called from fork_exit(). Just acquire the correct locks and
* let fork do the rest of the work.
*/
Commit 1/14 of sched_lock decomposition. - Move all scheduler locking into the schedulers utilizing a technique similar to solaris's container locking. - A per-process spinlock is now used to protect the queue of threads, thread count, suspension count, p_sflags, and other process related scheduling fields. - The new thread lock is actually a pointer to a spinlock for the container that the thread is currently owned by. The container may be a turnstile, sleepqueue, or run queue. - thread_lock() is now used to protect access to thread related scheduling fields. thread_unlock() unlocks the lock and thread_set_lock() implements the transition from one lock to another. - A new "blocked_lock" is used in cases where it is not safe to hold the actual thread's lock yet we must prevent access to the thread. - sched_throw() and sched_fork_exit() are introduced to allow the schedulers to fix-up locking at these points. - Add some minor infrastructure for optionally exporting scheduler statistics that were invaluable in solving performance problems with this patch. Generally these statistics allow you to differentiate between different causes of context switches. Tested by: kris, current@ Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc. Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:50:30 +00:00
void
- Move some common code out of sched_fork_exit() and back into fork_exit().
2007-06-12 07:47:09 +00:00
sched_fork_exit(struct thread *td)
Commit 1/14 of sched_lock decomposition. - Move all scheduler locking into the schedulers utilizing a technique similar to solaris's container locking. - A per-process spinlock is now used to protect the queue of threads, thread count, suspension count, p_sflags, and other process related scheduling fields. - The new thread lock is actually a pointer to a spinlock for the container that the thread is currently owned by. The container may be a turnstile, sleepqueue, or run queue. - thread_lock() is now used to protect access to thread related scheduling fields. thread_unlock() unlocks the lock and thread_set_lock() implements the transition from one lock to another. - A new "blocked_lock" is used in cases where it is not safe to hold the actual thread's lock yet we must prevent access to the thread. - sched_throw() and sched_fork_exit() are introduced to allow the schedulers to fix-up locking at these points. - Add some minor infrastructure for optionally exporting scheduler statistics that were invaluable in solving performance problems with this patch. Generally these statistics allow you to differentiate between different causes of context switches. Tested by: kris, current@ Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc. Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:50:30 +00:00
{
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
struct tdq *tdq;
int cpuid;
Commit 1/14 of sched_lock decomposition. - Move all scheduler locking into the schedulers utilizing a technique similar to solaris's container locking. - A per-process spinlock is now used to protect the queue of threads, thread count, suspension count, p_sflags, and other process related scheduling fields. - The new thread lock is actually a pointer to a spinlock for the container that the thread is currently owned by. The container may be a turnstile, sleepqueue, or run queue. - thread_lock() is now used to protect access to thread related scheduling fields. thread_unlock() unlocks the lock and thread_set_lock() implements the transition from one lock to another. - A new "blocked_lock" is used in cases where it is not safe to hold the actual thread's lock yet we must prevent access to the thread. - sched_throw() and sched_fork_exit() are introduced to allow the schedulers to fix-up locking at these points. - Add some minor infrastructure for optionally exporting scheduler statistics that were invaluable in solving performance problems with this patch. Generally these statistics allow you to differentiate between different causes of context switches. Tested by: kris, current@ Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc. Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:50:30 +00:00
/*
* Finish setting up thread glue so that it begins execution in a
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
* non-nested critical section with the scheduler lock held.
Commit 1/14 of sched_lock decomposition. - Move all scheduler locking into the schedulers utilizing a technique similar to solaris's container locking. - A per-process spinlock is now used to protect the queue of threads, thread count, suspension count, p_sflags, and other process related scheduling fields. - The new thread lock is actually a pointer to a spinlock for the container that the thread is currently owned by. The container may be a turnstile, sleepqueue, or run queue. - thread_lock() is now used to protect access to thread related scheduling fields. thread_unlock() unlocks the lock and thread_set_lock() implements the transition from one lock to another. - A new "blocked_lock" is used in cases where it is not safe to hold the actual thread's lock yet we must prevent access to the thread. - sched_throw() and sched_fork_exit() are introduced to allow the schedulers to fix-up locking at these points. - Add some minor infrastructure for optionally exporting scheduler statistics that were invaluable in solving performance problems with this patch. Generally these statistics allow you to differentiate between different causes of context switches. Tested by: kris, current@ Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc. Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:50:30 +00:00
*/
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
cpuid = PCPU_GET(cpuid);
tdq = TDQ_CPU(cpuid);
if (TD_IS_IDLETHREAD(td))
td->td_lock = TDQ_LOCKPTR(tdq);
MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
td->td_oncpu = cpuid;
- Reassign the thread queue lock to newtd prior to switching. Assigning after the switch leads to a race where the outgoing thread still owns the local queue lock while another cpu may switch it in. This race is only possible on machines where cpu_switch can take significantly longer on different cpus which in practice means HTT machines with unfair thread scheduling algorithms. Found by: kris (of course) Approved by: re
2007-10-02 01:30:18 +00:00
TDQ_LOCK_ASSERT(tdq, MA_OWNED | MA_NOTRECURSED);
- Re-implement lock profiling in such a way that it no longer breaks the ABI when enabled. There is no longer an embedded lock_profile_object in each lock. Instead a list of lock_profile_objects is kept per-thread for each lock it may own. The cnt_hold statistic is now always 0 to facilitate this. - Support shared locking by tracking individual lock instances and statistics in the per-thread per-instance lock_profile_object. - Make the lock profiling hash table a per-cpu singly linked list with a per-cpu static lock_prof allocator. This removes the need for an array of spinlocks and reduces cache contention between cores. - Use a seperate hash for spinlocks and other locks so that only a critical_enter() is required and not a spinlock_enter() to modify the per-cpu tables. - Count time spent spinning in the lock statistics. - Remove the LOCK_PROFILE_SHARED option as it is always supported now. - Specifically drop and release the scheduler locks in both schedulers since we track owners now. In collaboration with: Kip Macy Sponsored by: Nokia
2007-12-15 23:13:31 +00:00
lock_profile_obtain_lock_success(
&TDQ_LOCKPTR(tdq)->lock_object, 0, 0, __FILE__, __LINE__);
trace thread running state when a thread is run for the first time This applies to both KTR_SCHED and DTrace sched:::on-cpu tracing. MFC after: 10 days
2017-03-11 15:57:41 +00:00
KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "running",
"prio:%d", td->td_priority);
SDT_PROBE0(sched, , , on__cpu);
Commit 1/14 of sched_lock decomposition. - Move all scheduler locking into the schedulers utilizing a technique similar to solaris's container locking. - A per-process spinlock is now used to protect the queue of threads, thread count, suspension count, p_sflags, and other process related scheduling fields. - The new thread lock is actually a pointer to a spinlock for the container that the thread is currently owned by. The container may be a turnstile, sleepqueue, or run queue. - thread_lock() is now used to protect access to thread related scheduling fields. thread_unlock() unlocks the lock and thread_set_lock() implements the transition from one lock to another. - A new "blocked_lock" is used in cases where it is not safe to hold the actual thread's lock yet we must prevent access to the thread. - sched_throw() and sched_fork_exit() are introduced to allow the schedulers to fix-up locking at these points. - Add some minor infrastructure for optionally exporting scheduler statistics that were invaluable in solving performance problems with this patch. Generally these statistics allow you to differentiate between different causes of context switches. Tested by: kris, current@ Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc. Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
2007-06-04 23:50:30 +00:00
}
- Implement generic macros for producing KTR records that are compatible with src/tools/sched/schedgraph.py. This allows developers to quickly create a graphical view of ktr data for any resource in the system. - Add sched_tdname() and the pcpu field 'name' for quickly and uniformly identifying records associated with a thread or cpu. - Reimplement the KTR_SCHED traces using the new generic facility. Obtained from: attilio Discussed with: jhb Sponsored by: Nokia
2009-01-17 07:17:57 +00:00
/*
* Create on first use to catch odd startup conditons.
*/
char *
sched_tdname(struct thread *td)
{
#ifdef KTR
struct td_sched *ts;
Get rid of struct proc p_sched and struct thread td_sched pointers. p_sched is unused. The struct td_sched is always co-allocated with the struct thread, except for the thread0. Avoid useless indirection, instead calculate td_sched location using simple pointer arithmetic in td_get_sched(9). For thread0, which is statically allocated, create a structure to emulate layout of the dynamic allocation. Reviewed by: jhb (previous version) Sponsored by: The FreeBSD Foundation Differential revision: https://reviews.freebsd.org/D6711
2016-06-05 17:04:03 +00:00
ts = td_get_sched(td);
- Implement generic macros for producing KTR records that are compatible with src/tools/sched/schedgraph.py. This allows developers to quickly create a graphical view of ktr data for any resource in the system. - Add sched_tdname() and the pcpu field 'name' for quickly and uniformly identifying records associated with a thread or cpu. - Reimplement the KTR_SCHED traces using the new generic facility. Obtained from: attilio Discussed with: jhb Sponsored by: Nokia
2009-01-17 07:17:57 +00:00
if (ts->ts_name[0] == '\0')
snprintf(ts->ts_name, sizeof(ts->ts_name),
"%s tid %d", td->td_name, td->td_tid);
return (ts->ts_name);
#else
return (td->td_name);
#endif
}
Add a new sched_clear_name() method to the scheduler interface to clear the cached name used for KTR_SCHED traces when a thread's name changes. This way KTR_SCHED traces (and thus schedgraph) will notice when a thread's name changes, most commonly via execve(). MFC after: 2 weeks
2012-03-08 19:41:05 +00:00
#ifdef KTR
void
sched_clear_tdname(struct thread *td)
{
struct td_sched *ts;
Get rid of struct proc p_sched and struct thread td_sched pointers. p_sched is unused. The struct td_sched is always co-allocated with the struct thread, except for the thread0. Avoid useless indirection, instead calculate td_sched location using simple pointer arithmetic in td_get_sched(9). For thread0, which is statically allocated, create a structure to emulate layout of the dynamic allocation. Reviewed by: jhb (previous version) Sponsored by: The FreeBSD Foundation Differential revision: https://reviews.freebsd.org/D6711
2016-06-05 17:04:03 +00:00
ts = td_get_sched(td);
Add a new sched_clear_name() method to the scheduler interface to clear the cached name used for KTR_SCHED traces when a thread's name changes. This way KTR_SCHED traces (and thus schedgraph) will notice when a thread's name changes, most commonly via execve(). MFC after: 2 weeks
2012-03-08 19:41:05 +00:00
ts->ts_name[0] = '\0';
}
#endif
Introduce a new sysctl, kern.sched.topology_spec, that returns an XML dump of detected ULE CPU topology. This dump can be used to check the topology detection and for general system information. An example of CPU topology dump is: kern.sched.topology_spec: <groups> <group level="1" cache-level="0"> <cpu count="8" mask="0xff">0, 1, 2, 3, 4, 5, 6, 7</cpu> <flags></flags> <children> <group level="2" cache-level="0"> <cpu count="4" mask="0xf">0, 1, 2, 3</cpu> <flags></flags> </group> <group level="2" cache-level="0"> <cpu count="4" mask="0xf0">4, 5, 6, 7</cpu> <flags></flags> </group> </children> </group> </groups> Reviewed by: jeff Approved by: gnn (mentor)
2008-10-29 13:36:23 +00:00
#ifdef SMP
/*
* Build the CPU topology dump string. Is recursively called to collect
* the topology tree.
*/
static int
sysctl_kern_sched_topology_spec_internal(struct sbuf *sb, struct cpu_group *cg,
int indent)
{
Commit the support for removing cpumask_t and replacing it directly with cpuset_t objects. That is going to offer the underlying support for a simple bump of MAXCPU and then support for number of cpus > 32 (as it is today). Right now, cpumask_t is an int, 32 bits on all our supported architecture. cpumask_t on the other side is implemented as an array of longs, and easilly extendible by definition. The architectures touched by this commit are the following: - amd64 - i386 - pc98 - arm - ia64 - XEN while the others are still missing. Userland is believed to be fully converted with the changes contained here. Some technical notes: - This commit may be considered an ABI nop for all the architectures different from amd64 and ia64 (and sparc64 in the future) - per-cpu members, which are now converted to cpuset_t, needs to be accessed avoiding migration, because the size of cpuset_t should be considered unknown - size of cpuset_t objects is different from kernel and userland (this is primirally done in order to leave some more space in userland to cope with KBI extensions). If you need to access kernel cpuset_t from the userland please refer to example in this patch on how to do that correctly (kgdb may be a good source, for example). - Support for other architectures is going to be added soon - Only MAXCPU for amd64 is bumped now The patch has been tested by sbruno and Nicholas Esborn on opteron 4 x 12 pack CPUs. More testing on big SMP is expected to came soon. pluknet tested the patch with his 8-ways on both amd64 and i386. Tested by: pluknet, sbruno, gianni, Nicholas Esborn Reviewed by: jeff, jhb, sbruno
2011-05-05 14:39:14 +00:00
char cpusetbuf[CPUSETBUFSIZ];
Introduce a new sysctl, kern.sched.topology_spec, that returns an XML dump of detected ULE CPU topology. This dump can be used to check the topology detection and for general system information. An example of CPU topology dump is: kern.sched.topology_spec: <groups> <group level="1" cache-level="0"> <cpu count="8" mask="0xff">0, 1, 2, 3, 4, 5, 6, 7</cpu> <flags></flags> <children> <group level="2" cache-level="0"> <cpu count="4" mask="0xf">0, 1, 2, 3</cpu> <flags></flags> </group> <group level="2" cache-level="0"> <cpu count="4" mask="0xf0">4, 5, 6, 7</cpu> <flags></flags> </group> </children> </group> </groups> Reviewed by: jeff Approved by: gnn (mentor)
2008-10-29 13:36:23 +00:00
int i, first;
sbuf_printf(sb, "%*s<group level=\"%d\" cache-level=\"%d\">\n", indent,
kern.sched.topology_spec sysctl: use step of 1 for group levels numeration This is just a cosmetic change for prettier output. 'indent' variable/parameter serves two purposes: it specifies whitespace indentation level and also implies cpu group level/depth. It would have been better to split those two uses, but for now just a simple change. MFC after: 1 week
2010-09-18 11:16:43 +00:00
"", 1 + indent / 2, cg->cg_level);
Commit the support for removing cpumask_t and replacing it directly with cpuset_t objects. That is going to offer the underlying support for a simple bump of MAXCPU and then support for number of cpus > 32 (as it is today). Right now, cpumask_t is an int, 32 bits on all our supported architecture. cpumask_t on the other side is implemented as an array of longs, and easilly extendible by definition. The architectures touched by this commit are the following: - amd64 - i386 - pc98 - arm - ia64 - XEN while the others are still missing. Userland is believed to be fully converted with the changes contained here. Some technical notes: - This commit may be considered an ABI nop for all the architectures different from amd64 and ia64 (and sparc64 in the future) - per-cpu members, which are now converted to cpuset_t, needs to be accessed avoiding migration, because the size of cpuset_t should be considered unknown - size of cpuset_t objects is different from kernel and userland (this is primirally done in order to leave some more space in userland to cope with KBI extensions). If you need to access kernel cpuset_t from the userland please refer to example in this patch on how to do that correctly (kgdb may be a good source, for example). - Support for other architectures is going to be added soon - Only MAXCPU for amd64 is bumped now The patch has been tested by sbruno and Nicholas Esborn on opteron 4 x 12 pack CPUs. More testing on big SMP is expected to came soon. pluknet tested the patch with his 8-ways on both amd64 and i386. Tested by: pluknet, sbruno, gianni, Nicholas Esborn Reviewed by: jeff, jhb, sbruno
2011-05-05 14:39:14 +00:00
sbuf_printf(sb, "%*s <cpu count=\"%d\" mask=\"%s\">", indent, "",
cg->cg_count, cpusetobj_strprint(cpusetbuf, &cg->cg_mask));
Introduce a new sysctl, kern.sched.topology_spec, that returns an XML dump of detected ULE CPU topology. This dump can be used to check the topology detection and for general system information. An example of CPU topology dump is: kern.sched.topology_spec: <groups> <group level="1" cache-level="0"> <cpu count="8" mask="0xff">0, 1, 2, 3, 4, 5, 6, 7</cpu> <flags></flags> <children> <group level="2" cache-level="0"> <cpu count="4" mask="0xf">0, 1, 2, 3</cpu> <flags></flags> </group> <group level="2" cache-level="0"> <cpu count="4" mask="0xf0">4, 5, 6, 7</cpu> <flags></flags> </group> </children> </group> </groups> Reviewed by: jeff Approved by: gnn (mentor)
2008-10-29 13:36:23 +00:00
first = TRUE;
for (i = 0; i < MAXCPU; i++) {
Commit the support for removing cpumask_t and replacing it directly with cpuset_t objects. That is going to offer the underlying support for a simple bump of MAXCPU and then support for number of cpus > 32 (as it is today). Right now, cpumask_t is an int, 32 bits on all our supported architecture. cpumask_t on the other side is implemented as an array of longs, and easilly extendible by definition. The architectures touched by this commit are the following: - amd64 - i386 - pc98 - arm - ia64 - XEN while the others are still missing. Userland is believed to be fully converted with the changes contained here. Some technical notes: - This commit may be considered an ABI nop for all the architectures different from amd64 and ia64 (and sparc64 in the future) - per-cpu members, which are now converted to cpuset_t, needs to be accessed avoiding migration, because the size of cpuset_t should be considered unknown - size of cpuset_t objects is different from kernel and userland (this is primirally done in order to leave some more space in userland to cope with KBI extensions). If you need to access kernel cpuset_t from the userland please refer to example in this patch on how to do that correctly (kgdb may be a good source, for example). - Support for other architectures is going to be added soon - Only MAXCPU for amd64 is bumped now The patch has been tested by sbruno and Nicholas Esborn on opteron 4 x 12 pack CPUs. More testing on big SMP is expected to came soon. pluknet tested the patch with his 8-ways on both amd64 and i386. Tested by: pluknet, sbruno, gianni, Nicholas Esborn Reviewed by: jeff, jhb, sbruno
2011-05-05 14:39:14 +00:00
if (CPU_ISSET(i, &cg->cg_mask)) {
Introduce a new sysctl, kern.sched.topology_spec, that returns an XML dump of detected ULE CPU topology. This dump can be used to check the topology detection and for general system information. An example of CPU topology dump is: kern.sched.topology_spec: <groups> <group level="1" cache-level="0"> <cpu count="8" mask="0xff">0, 1, 2, 3, 4, 5, 6, 7</cpu> <flags></flags> <children> <group level="2" cache-level="0"> <cpu count="4" mask="0xf">0, 1, 2, 3</cpu> <flags></flags> </group> <group level="2" cache-level="0"> <cpu count="4" mask="0xf0">4, 5, 6, 7</cpu> <flags></flags> </group> </children> </group> </groups> Reviewed by: jeff Approved by: gnn (mentor)
2008-10-29 13:36:23 +00:00
if (!first)
sbuf_printf(sb, ", ");
else
first = FALSE;
sbuf_printf(sb, "%d", i);
}
}
sbuf_printf(sb, "</cpu>\n");
if (cg->cg_flags != 0) {
A cosmetic change - don't output empty <flags>.
2010-07-15 13:46:30 +00:00
sbuf_printf(sb, "%*s <flags>", indent, "");
Introduce a new sysctl, kern.sched.topology_spec, that returns an XML dump of detected ULE CPU topology. This dump can be used to check the topology detection and for general system information. An example of CPU topology dump is: kern.sched.topology_spec: <groups> <group level="1" cache-level="0"> <cpu count="8" mask="0xff">0, 1, 2, 3, 4, 5, 6, 7</cpu> <flags></flags> <children> <group level="2" cache-level="0"> <cpu count="4" mask="0xf">0, 1, 2, 3</cpu> <flags></flags> </group> <group level="2" cache-level="0"> <cpu count="4" mask="0xf0">4, 5, 6, 7</cpu> <flags></flags> </group> </children> </group> </groups> Reviewed by: jeff Approved by: gnn (mentor)
2008-10-29 13:36:23 +00:00
if ((cg->cg_flags & CG_FLAG_HTT) != 0)
Cosmetic change to XML - less ugly newlines
2010-06-10 11:01:17 +00:00
sbuf_printf(sb, "<flag name=\"HTT\">HTT group</flag>");
Unconfuse THREAD and SMT flags
2010-06-10 11:48:14 +00:00
if ((cg->cg_flags & CG_FLAG_THREAD) != 0)
sbuf_printf(sb, "<flag name=\"THREAD\">THREAD group</flag>");
- Remove the bogus idle thread state code. This may have a race in it and it only optimized out an ipi or mwait in very few cases. - Skip the adaptive idle code when running on SMT or HTT cores. This just wastes cpu time that could be used on a busy thread on the same core. - Rename CG_FLAG_THREAD to CG_FLAG_SMT to be more descriptive. Re-use CG_FLAG_THREAD to mean SMT or HTT. Sponsored by: Nokia
2009-04-29 03:15:43 +00:00
if ((cg->cg_flags & CG_FLAG_SMT) != 0)
Unconfuse THREAD and SMT flags
2010-06-10 11:48:14 +00:00
sbuf_printf(sb, "<flag name=\"SMT\">SMT group</flag>");
A cosmetic change - don't output empty <flags>.
2010-07-15 13:46:30 +00:00
sbuf_printf(sb, "</flags>\n");
Introduce a new sysctl, kern.sched.topology_spec, that returns an XML dump of detected ULE CPU topology. This dump can be used to check the topology detection and for general system information. An example of CPU topology dump is: kern.sched.topology_spec: <groups> <group level="1" cache-level="0"> <cpu count="8" mask="0xff">0, 1, 2, 3, 4, 5, 6, 7</cpu> <flags></flags> <children> <group level="2" cache-level="0"> <cpu count="4" mask="0xf">0, 1, 2, 3</cpu> <flags></flags> </group> <group level="2" cache-level="0"> <cpu count="4" mask="0xf0">4, 5, 6, 7</cpu> <flags></flags> </group> </children> </group> </groups> Reviewed by: jeff Approved by: gnn (mentor)
2008-10-29 13:36:23 +00:00
}
if (cg->cg_children > 0) {
sbuf_printf(sb, "%*s <children>\n", indent, "");
for (i = 0; i < cg->cg_children; i++)
sysctl_kern_sched_topology_spec_internal(sb,
&cg->cg_child[i], indent+2);
sbuf_printf(sb, "%*s </children>\n", indent, "");
}
sbuf_printf(sb, "%*s</group>\n", indent, "");
return (0);
}
/*
* Sysctl handler for retrieving topology dump. It's a wrapper for
* the recursive sysctl_kern_smp_topology_spec_internal().
*/
static int
sysctl_kern_sched_topology_spec(SYSCTL_HANDLER_ARGS)
{
struct sbuf *topo;
int err;
KASSERT(cpu_top != NULL, ("cpu_top isn't initialized"));
Use sbuf_new_for_sysctl() instead of plain sbuf_new() to ensure sysctl string returned to userland is nulterminated. PR: 195668
2015-03-14 18:42:30 +00:00
topo = sbuf_new_for_sysctl(NULL, NULL, 512, req);
Introduce a new sysctl, kern.sched.topology_spec, that returns an XML dump of detected ULE CPU topology. This dump can be used to check the topology detection and for general system information. An example of CPU topology dump is: kern.sched.topology_spec: <groups> <group level="1" cache-level="0"> <cpu count="8" mask="0xff">0, 1, 2, 3, 4, 5, 6, 7</cpu> <flags></flags> <children> <group level="2" cache-level="0"> <cpu count="4" mask="0xf">0, 1, 2, 3</cpu> <flags></flags> </group> <group level="2" cache-level="0"> <cpu count="4" mask="0xf0">4, 5, 6, 7</cpu> <flags></flags> </group> </children> </group> </groups> Reviewed by: jeff Approved by: gnn (mentor)
2008-10-29 13:36:23 +00:00
if (topo == NULL)
return (ENOMEM);
sbuf_printf(topo, "<groups>\n");
err = sysctl_kern_sched_topology_spec_internal(topo, cpu_top, 1);
sbuf_printf(topo, "</groups>\n");
if (err == 0) {
Use sbuf_new_for_sysctl() instead of plain sbuf_new() to ensure sysctl string returned to userland is nulterminated. PR: 195668
2015-03-14 18:42:30 +00:00
err = sbuf_finish(topo);
Introduce a new sysctl, kern.sched.topology_spec, that returns an XML dump of detected ULE CPU topology. This dump can be used to check the topology detection and for general system information. An example of CPU topology dump is: kern.sched.topology_spec: <groups> <group level="1" cache-level="0"> <cpu count="8" mask="0xff">0, 1, 2, 3, 4, 5, 6, 7</cpu> <flags></flags> <children> <group level="2" cache-level="0"> <cpu count="4" mask="0xf">0, 1, 2, 3</cpu> <flags></flags> </group> <group level="2" cache-level="0"> <cpu count="4" mask="0xf0">4, 5, 6, 7</cpu> <flags></flags> </group> </children> </group> </groups> Reviewed by: jeff Approved by: gnn (mentor)
2008-10-29 13:36:23 +00:00
}
sbuf_delete(topo);
return (err);
}
Add sysctl kern.sched.cpusetsize to export the size of kernel cpuset, also add sysconf() key _SC_CPUSET_SIZE to get sysctl value. Submitted by: gcooper
2010-10-29 13:31:10 +00:00
Introduce a new sysctl, kern.sched.topology_spec, that returns an XML dump of detected ULE CPU topology. This dump can be used to check the topology detection and for general system information. An example of CPU topology dump is: kern.sched.topology_spec: <groups> <group level="1" cache-level="0"> <cpu count="8" mask="0xff">0, 1, 2, 3, 4, 5, 6, 7</cpu> <flags></flags> <children> <group level="2" cache-level="0"> <cpu count="4" mask="0xf">0, 1, 2, 3</cpu> <flags></flags> </group> <group level="2" cache-level="0"> <cpu count="4" mask="0xf0">4, 5, 6, 7</cpu> <flags></flags> </group> </children> </group> </groups> Reviewed by: jeff Approved by: gnn (mentor)
2008-10-29 13:36:23 +00:00
#endif
Some minor tunings/cleanups inspired by bde@ after previous commits: - remove extra dynamic variable initializations; - restore (4BSD) and implement (ULE) hogticks variable setting; - make sched_rr_interval() more tolerant to options; - restore (4BSD) and implement (ULE) kern.sched.quantum sysctl, a more user-friendly wrapper for sched_slice; - tune some sysctl descriptions; - make some style fixes.
2012-08-10 19:02:49 +00:00
static int
sysctl_kern_quantum(SYSCTL_HANDLER_ARGS)
{
int error, new_val, period;
period = 1000000 / realstathz;
new_val = period * sched_slice;
error = sysctl_handle_int(oidp, &new_val, 0, req);
Some more minor tunings inspired by bde@.
2012-08-11 20:24:39 +00:00
if (error != 0 || req->newptr == NULL)
Some minor tunings/cleanups inspired by bde@ after previous commits: - remove extra dynamic variable initializations; - restore (4BSD) and implement (ULE) hogticks variable setting; - make sched_rr_interval() more tolerant to options; - restore (4BSD) and implement (ULE) kern.sched.quantum sysctl, a more user-friendly wrapper for sched_slice; - tune some sysctl descriptions; - make some style fixes.
2012-08-10 19:02:49 +00:00
return (error);
if (new_val <= 0)
return (EINVAL);
Some more minor tunings inspired by bde@.
2012-08-11 20:24:39 +00:00
sched_slice = imax(1, (new_val + period / 2) / period);
- Change ULE to use dynamic slice sizes for the timeshare queue in order to further reduce latency for threads in this queue. This should help as threads transition from realtime to timeshare. The latency is bound to a max of sched_slice until we have more than sched_slice / 6 threads runnable. Then the min slice is allotted to all threads and latency becomes (nthreads - 1) * min_slice. Discussed with: mav
2012-11-08 01:46:47 +00:00
sched_slice_min = sched_slice / SCHED_SLICE_MIN_DIVISOR;
Some more minor tunings inspired by bde@.
2012-08-11 20:24:39 +00:00
hogticks = imax(1, (2 * hz * sched_slice + realstathz / 2) /
realstathz);
Some minor tunings/cleanups inspired by bde@ after previous commits: - remove extra dynamic variable initializations; - restore (4BSD) and implement (ULE) hogticks variable setting; - make sched_rr_interval() more tolerant to options; - restore (4BSD) and implement (ULE) kern.sched.quantum sysctl, a more user-friendly wrapper for sched_slice; - tune some sysctl descriptions; - make some style fixes.
2012-08-10 19:02:49 +00:00
return (0);
}
- Restore runq to manipulating threads directly by putting runq links and rqindex back in struct thread. - Compile kern_switch.c independently again and stop #include'ing it from schedulers. - Remove the ts_thread backpointers and convert most code to go from struct thread to struct td_sched. - Cleanup the ts_flags #define garbage that was causing us to sometimes do things that expanded to td->td_sched->ts_thread->td_flags in 4BSD. - Export the kern.sched sysctl node in sysctl.h
2008-03-20 05:51:16 +00:00
SYSCTL_NODE(_kern, OID_AUTO, sched, CTLFLAG_RW, 0, "Scheduler");
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
SYSCTL_STRING(_kern_sched, OID_AUTO, name, CTLFLAG_RD, "ULE", 0,
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
"Scheduler name");
Some minor tunings/cleanups inspired by bde@ after previous commits: - remove extra dynamic variable initializations; - restore (4BSD) and implement (ULE) hogticks variable setting; - make sched_rr_interval() more tolerant to options; - restore (4BSD) and implement (ULE) kern.sched.quantum sysctl, a more user-friendly wrapper for sched_slice; - tune some sysctl descriptions; - make some style fixes.
2012-08-10 19:02:49 +00:00
SYSCTL_PROC(_kern_sched, OID_AUTO, quantum, CTLTYPE_INT | CTLFLAG_RW,
NULL, 0, sysctl_kern_quantum, "I",
Some more minor tunings inspired by bde@.
2012-08-11 20:24:39 +00:00
"Quantum for timeshare threads in microseconds");
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
SYSCTL_INT(_kern_sched, OID_AUTO, slice, CTLFLAG_RW, &sched_slice, 0,
Some more minor tunings inspired by bde@.
2012-08-11 20:24:39 +00:00
"Quantum for timeshare threads in stathz ticks");
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
SYSCTL_INT(_kern_sched, OID_AUTO, interact, CTLFLAG_RW, &sched_interact, 0,
Some more minor tunings inspired by bde@.
2012-08-11 20:24:39 +00:00
"Interactivity score threshold");
SYSCTL_INT(_kern_sched, OID_AUTO, preempt_thresh, CTLFLAG_RW,
&preempt_thresh, 0,
"Maximal (lowest) priority for preemption");
SYSCTL_INT(_kern_sched, OID_AUTO, static_boost, CTLFLAG_RW, &static_boost, 0,
"Assign static kernel priorities to sleeping threads");
SYSCTL_INT(_kern_sched, OID_AUTO, idlespins, CTLFLAG_RW, &sched_idlespins, 0,
"Number of times idle thread will spin waiting for new work");
SYSCTL_INT(_kern_sched, OID_AUTO, idlespinthresh, CTLFLAG_RW,
&sched_idlespinthresh, 0,
"Threshold before we will permit idle thread spinning");
Major revamp of ULE's cpu load balancing: - Switch back to direct modification of remote CPU run queues. This added a lot of complexity with questionable gain. It's easy enough to reimplement if it's shown to help on huge machines. - Re-implement the old tdq_transfer() call as tdq_pickidle(). Change sched_add() so we have selectable cpu choosers and simplify the logic a bit here. - Implement tdq_pickpri() as the new default cpu chooser. This algorithm is similar to Solaris in that it tries to always run the threads with the best priorities. It is actually slightly more complex than solaris's algorithm because we also tend to favor the local cpu over other cpus which has a boost in latency but also potentially enables cache sharing between the waking thread and the woken thread. - Add a bunch of tunables that can be used to measure effects of different load balancing strategies. Most of these will go away once the algorithm is more definite. - Add a new mechanism to steal threads from busy cpus when we idle. This is enabled with kern.sched.steal_busy and kern.sched.busy_thresh. The threshold is the required length of a tdq's run queue before another cpu will be able to steal runnable threads. This prevents most queue imbalances that contribute the long latencies.
2007-01-19 21:56:08 +00:00
#ifdef SMP
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
SYSCTL_INT(_kern_sched, OID_AUTO, affinity, CTLFLAG_RW, &affinity, 0,
"Number of hz ticks to keep thread affinity for");
SYSCTL_INT(_kern_sched, OID_AUTO, balance, CTLFLAG_RW, &rebalance, 0,
"Enables the long-term load balancer");
- Move the rebalancer back into hardclock to prevent potential softclock starvation caused by unbalanced interrupt loads. - Change the rebalancer to work on stathz ticks but retain randomization. - Simplify locking in tdq_idled() to use the tdq_lock_pair() rather than complex sequences of locks to avoid deadlock. Reported by: kris Approved by: re
2007-10-02 00:36:06 +00:00
SYSCTL_INT(_kern_sched, OID_AUTO, balance_interval, CTLFLAG_RW,
&balance_interval, 0,
Some minor tunings/cleanups inspired by bde@ after previous commits: - remove extra dynamic variable initializations; - restore (4BSD) and implement (ULE) hogticks variable setting; - make sched_rr_interval() more tolerant to options; - restore (4BSD) and implement (ULE) kern.sched.quantum sysctl, a more user-friendly wrapper for sched_slice; - tune some sysctl descriptions; - make some style fixes.
2012-08-10 19:02:49 +00:00
"Average period in stathz ticks to run the long-term balancer");
ULE 3.0: Fine grain scheduler locking and affinity improvements. This has been in development for over 6 months as SCHED_SMP. - Implement one spin lock per thread-queue. Threads assigned to a run-queue point to this lock via td_lock. - Improve the facility for assigning threads to CPUs now that sched_lock contention no longer dominates scheduling decisions on larger SMP machines. - Re-write idle time stealing in an attempt to make it less damaging to general performance. This is still disabled by default. See kern.sched.steal_idle. - Call the long-term load balancer from a callout rather than sched_clock() so there are no locks held. This is disabled by default. See kern.sched.balance. - Parameterize many scheduling decisions via sysctls. Try to document these via sysctl descriptions. - General structural and naming cleanups. - Document each function with comments. Tested by: current@ amd64, x86, UP, SMP. Approved by: re
2007-07-17 22:53:23 +00:00
SYSCTL_INT(_kern_sched, OID_AUTO, steal_idle, CTLFLAG_RW, &steal_idle, 0,
"Attempts to steal work from other cores before idling");
- Refine the load balancer to improve buildkernel times on dual core machines. - Leave the long-term load balancer running by default once per second. - Enable stealing load from the idle thread only when the remote processor has more than two transferable tasks. Setting this to one further improves buildworld. Setting it higher improves mysql. - Remove the bogus pick_zero option. I had not intended to commit this. - Entirely disallow migration for threads with SRQ_YIELDING set. This balances out the extra migration allowed for with the load balancers. It also makes pick_pri perform better as I had anticipated. Tested by: Dmitry Morozovsky <marck@rinet.ru> Approved by: re
2007-07-19 20:03:15 +00:00
SYSCTL_INT(_kern_sched, OID_AUTO, steal_thresh, CTLFLAG_RW, &steal_thresh, 0,
Some more minor tunings inspired by bde@.
2012-08-11 20:24:39 +00:00
"Minimum load on remote CPU before we'll steal");
Decrease latency by not wrapping the idle loop's potentially lengthy search for a thread to steal inside a critical section. Since this allows the search to be preempted, restart the search if preemption happens since the search results found earlier may no longer be valid. Decrease the latency of starting a thread that may be assigned to this CPU during the search by polling for incoming threads during the search and switching to that thread instead of continuing the search. Test for stale search results and restart the search before going through the expense of calling tdq_lock_pair(). Retry some tests after grabbing the locks since things may have changed while waiting to get both locks. Eliminate special case handling for stealing from an SMT peer that uses 1 as the steal threshold. This can only succeed if a thread has been assigned but our SMT peer has not yet started executing it. This is quite rare and when it happens the other SMT thread is generally waiting for the same tdq lock that we hold. Basically both SMT threads are racing to grab the same spin lock. Add the kern.sched.always_steal knob from a ULE patch by jeff@. Incorporate another idea from Jeff's ULE patch. If the sched_switch() detects that the CPU is about to go idle, try to steal a thread before switching to the idle thread. Since the search for a thread to steal has to be done inside a critical section in this context, limit the impact on latency by adding the knob kern.sched.trysteal_limit to limit the topological distance of the search and don't restart the search if we detect stale results. If this search can't find an stealable thread, the idle loop can do a more complete search. Also poll for threads being assigned to this CPU during the search and switch to them instead of continuing the search. This change is responsibile for the majority of the improvement in parallel buildworld times. In sched_balance_group() change the minimum threshold from stealing a thread from 1 to 2. Poaching a newly assigned thread from a CPU that is waking up hasn't yet switched to that thread from idle is likely very rare and is likely to have the same lock race as is seen when stealing threads in the idle loop. Also use tdq_notify() to kick the destintation CPU instead of always sending an IPI. Update a stale comment, the number of transferable threads is not calculated. Reviewed by: kib (earlier version) Comments by: avg, jeff, mav MFC after: 1 month Differential Revision: https://reviews.freebsd.org/D12130
2018-02-23 00:12:51 +00:00
SYSCTL_INT(_kern_sched, OID_AUTO, trysteal_limit, CTLFLAG_RW, &trysteal_limit,
0, "Topological distance limit for stealing threads in sched_switch()");
SYSCTL_INT(_kern_sched, OID_AUTO, always_steal, CTLFLAG_RW, &always_steal, 0,
"Always run the stealer from the idle thread");
Introduce a new sysctl, kern.sched.topology_spec, that returns an XML dump of detected ULE CPU topology. This dump can be used to check the topology detection and for general system information. An example of CPU topology dump is: kern.sched.topology_spec: <groups> <group level="1" cache-level="0"> <cpu count="8" mask="0xff">0, 1, 2, 3, 4, 5, 6, 7</cpu> <flags></flags> <children> <group level="2" cache-level="0"> <cpu count="4" mask="0xf">0, 1, 2, 3</cpu> <flags></flags> </group> <group level="2" cache-level="0"> <cpu count="4" mask="0xf0">4, 5, 6, 7</cpu> <flags></flags> </group> </children> </group> </groups> Reviewed by: jeff Approved by: gnn (mentor)
2008-10-29 13:36:23 +00:00
SYSCTL_PROC(_kern_sched, OID_AUTO, topology_spec, CTLTYPE_STRING |
Don't take Giant for SMP status and cpu topology sysctls. Not only this lock doesn't play any role here, dirtying it slows down other things a little bit as giant-held checks (e.g. DROP_GIANT) are spread all over the kernel. MFC after: 1 week
2017-10-18 22:00:44 +00:00
CTLFLAG_MPSAFE | CTLFLAG_RD, NULL, 0, sysctl_kern_sched_topology_spec, "A",
Introduce a new sysctl, kern.sched.topology_spec, that returns an XML dump of detected ULE CPU topology. This dump can be used to check the topology detection and for general system information. An example of CPU topology dump is: kern.sched.topology_spec: <groups> <group level="1" cache-level="0"> <cpu count="8" mask="0xff">0, 1, 2, 3, 4, 5, 6, 7</cpu> <flags></flags> <children> <group level="2" cache-level="0"> <cpu count="4" mask="0xf">0, 1, 2, 3</cpu> <flags></flags> </group> <group level="2" cache-level="0"> <cpu count="4" mask="0xf0">4, 5, 6, 7</cpu> <flags></flags> </group> </children> </group> </groups> Reviewed by: jeff Approved by: gnn (mentor)
2008-10-29 13:36:23 +00:00
"XML dump of detected CPU topology");
Major revamp of ULE's cpu load balancing: - Switch back to direct modification of remote CPU run queues. This added a lot of complexity with questionable gain. It's easy enough to reimplement if it's shown to help on huge machines. - Re-implement the old tdq_transfer() call as tdq_pickidle(). Change sched_add() so we have selectable cpu choosers and simplify the logic a bit here. - Implement tdq_pickpri() as the new default cpu chooser. This algorithm is similar to Solaris in that it tries to always run the threads with the best priorities. It is actually slightly more complex than solaris's algorithm because we also tend to favor the local cpu over other cpus which has a boost in latency but also potentially enables cache sharing between the waking thread and the woken thread. - Add a bunch of tunables that can be used to measure effects of different load balancing strategies. Most of these will go away once the algorithm is more definite. - Add a new mechanism to steal threads from busy cpus when we idle. This is enabled with kern.sched.steal_busy and kern.sched.busy_thresh. The threshold is the required length of a tdq's run queue before another cpu will be able to steal runnable threads. This prevents most queue imbalances that contribute the long latencies.
2007-01-19 21:56:08 +00:00
#endif
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
- Redefine p_swtime and td_slptime as p_swtick and td_slptick. This changes the units from seconds to the value of 'ticks' when swapped in/out. ULE does not have a periodic timer that scans all threads in the system and as such maintaining a per-second counter is difficult. - Change computations requiring the unit in seconds to subtract ticks and divide by hz. This does make the wraparound condition hz times more frequent but this is still in the range of several months to years and the adverse effects are minimal. Approved by: re
2007-09-21 04:10:23 +00:00
/* ps compat. All cpu percentages from ULE are weighted. */
- Improve grammar. s/it's/its/. - Improve load long-term load balancer by always IPIing exactly once. Previously the delay after rebalancing could cause problems with uneven workloads. - Allow nice to have a linear effect on the interactivity score. This allows negatively niced programs to stay interactive longer. It may be useful with very expensive Xorg servers under high loads. In general it should not be necessary to alter the nice level to improve interactive response. We may also want to consider never allowing positively niced processes to become interactive at all. - Initialize ccpu to 0 rather than 0.0. The decimal point was leftover from when the code was copied from 4bsd. ccpu is 0 in ULE because ULE only exports weighted cpu values. Reported by: Steve Kargl (Load balancing problem) Approved by: re
2007-09-22 02:20:14 +00:00
static int ccpu = 0;
ULE 2.0: - Remove the double queue mechanism for timeshare threads. It was slow due to excess cache lines in play, caused suboptimal scheduling behavior with niced and other non-interactive processes, complicated priority lending, etc. - Use a circular queue with a floating starting index for timeshare threads. Enforces fairness by moving the insertion point closer to threads with worse priorities over time. - Give interactive timeshare threads real-time user-space priorities and place them on the realtime/ithd queue. - Select non-interactive timeshare thread priorities based on their cpu utilization over the last 10 seconds combined with the nice value. This gives us more sane priorities and behavior in a loaded system as compared to the old method of using the interactivity score. The interactive score quickly hit a ceiling if threads were non-interactive and penalized new hog threads. - Use one slice size for all threads. The slice is not currently dynamically set to adjust scheduling behavior of different threads. - Add some new sysctls for scheduling parameters. Bug fixes/Clean up: - Fix zeroing of td_sched after initialization in sched_fork_thread() caused by recent ksegrp removal. - Fix KSE interactivity issues related to frequent forking and exiting of kse threads. We simply disable the penalty for thread creation and exit for kse threads. - Cleanup the cpu estimator by using tickincr here as well. Keep ticks and ltick/ftick in the same frequency. Previously ticks were stathz and others were hz. - Lots of new and updated comments. - Many many others. Tested on: up x86/amd64, 8way amd64.
2007-01-04 08:56:25 +00:00
SYSCTL_INT(_kern, OID_AUTO, ccpu, CTLFLAG_RD, &ccpu, 0, "");
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