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freebsd-dev/sys/kern/sched_ule.c
Adrian Chadd e77f9fed15 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

2894 lines
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/*-
* Copyright (c) 2002-2007, Jeffrey Roberson <jeff@freebsd.org>
* 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.
*/
/*
* 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:
* ULE is the last three letters in schedule. It owes its name to a
* 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.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "opt_hwpmc_hooks.h"
#include "opt_sched.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kdb.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/limits.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/resource.h>
#include <sys/resourcevar.h>
#include <sys/sched.h>
#include <sys/sdt.h>
#include <sys/smp.h>
#include <sys/sx.h>
#include <sys/sysctl.h>
#include <sys/sysproto.h>
#include <sys/turnstile.h>
#include <sys/umtx.h>
#include <sys/vmmeter.h>
#include <sys/cpuset.h>
#include <sys/sbuf.h>
#ifdef HWPMC_HOOKS
#include <sys/pmckern.h>
#endif
#ifdef KDTRACE_HOOKS
#include <sys/dtrace_bsd.h>
int dtrace_vtime_active;
dtrace_vtime_switch_func_t dtrace_vtime_switch_func;
#endif
#include <machine/cpu.h>
#include <machine/smp.h>
#define KTR_ULE 0
#define TS_NAME_LEN (MAXCOMLEN + sizeof(" td ") + sizeof(__XSTRING(UINT_MAX)))
#define TDQ_NAME_LEN (sizeof("sched lock ") + sizeof(__XSTRING(MAXCPU)))
#define TDQ_LOADNAME_LEN (sizeof("CPU ") + sizeof(__XSTRING(MAXCPU)) - 1 + sizeof(" load"))
/*
* Thread scheduler specific section. All fields are protected
* by the thread lock.
*/
struct td_sched {
struct runq *ts_runq; /* Run-queue we're queued on. */
short ts_flags; /* TSF_* flags. */
int ts_cpu; /* CPU that we have affinity for. */
int ts_rltick; /* Real last tick, for affinity. */
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 */
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 */
#ifdef KTR
char ts_name[TS_NAME_LEN];
#endif
};
/* flags kept in ts_flags */
#define TSF_BOUND 0x0001 /* Thread can not migrate. */
#define TSF_XFERABLE 0x0002 /* Thread was added as transferable. */
static struct td_sched td_sched0;
#define THREAD_CAN_MIGRATE(td) ((td)->td_pinned == 0)
#define THREAD_CAN_SCHED(td, cpu) \
CPU_ISSET((cpu), &(td)->td_cpuset->cs_mask)
/*
* Priority ranges used for interactive and non-interactive timeshare
* 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.
*/
#define PRI_TIMESHARE_RANGE (PRI_MAX_TIMESHARE - PRI_MIN_TIMESHARE + 1)
#define PRI_INTERACT_RANGE ((PRI_TIMESHARE_RANGE - SCHED_PRI_NRESV) / 2)
#define PRI_BATCH_RANGE (PRI_TIMESHARE_RANGE - PRI_INTERACT_RANGE)
#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)
#define PRI_MAX_BATCH PRI_MAX_TIMESHARE
/*
* 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.
* SCHED_TICK_MAX: Maximum number of ticks before scaling back.
* 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)
#define SCHED_TICK_MAX (SCHED_TICK_TARG + hz)
#define SCHED_TICK_SHIFT 10
#define SCHED_TICK_HZ(ts) ((ts)->ts_ticks >> SCHED_TICK_SHIFT)
#define SCHED_TICK_TOTAL(ts) (max((ts)->ts_ltick - (ts)->ts_ftick, hz))
/*
* 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.
*
* PRI_RANGE: Priority range for utilization dependent priorities.
* PRI_NRESV: Number of nice values.
* 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.
*/
#define SCHED_PRI_NRESV (PRIO_MAX - PRIO_MIN)
#define SCHED_PRI_NHALF (SCHED_PRI_NRESV / 2)
#define SCHED_PRI_MIN (PRI_MIN_BATCH + SCHED_PRI_NHALF)
#define SCHED_PRI_MAX (PRI_MAX_BATCH - SCHED_PRI_NHALF)
#define SCHED_PRI_RANGE (SCHED_PRI_MAX - SCHED_PRI_MIN + 1)
#define SCHED_PRI_TICKS(ts) \
(SCHED_TICK_HZ((ts)) / \
(roundup(SCHED_TICK_TOTAL((ts)), SCHED_PRI_RANGE) / SCHED_PRI_RANGE))
#define SCHED_PRI_NICE(nice) (nice)
/*
* 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.
*
* SLP_RUN_MAX: Maximum amount of sleep time + run time we'll accumulate
* before throttling back.
* SLP_RUN_FORK: Maximum slp+run time to inherit at fork time.
* INTERACT_MAX: Maximum interactivity value. Smaller is better.
* INTERACT_THRESH: Threshold for placement on the current runq.
*/
#define SCHED_SLP_RUN_MAX ((hz * 5) << SCHED_TICK_SHIFT)
#define SCHED_SLP_RUN_FORK ((hz / 2) << SCHED_TICK_SHIFT)
#define SCHED_INTERACT_MAX (100)
#define SCHED_INTERACT_HALF (SCHED_INTERACT_MAX / 2)
#define SCHED_INTERACT_THRESH (30)
/*
* 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. */
/* Flags kept in td_flags. */
#define TDF_SLICEEND TDF_SCHED2 /* Thread time slice is over. */
/*
* 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.
* preempt_thresh: Priority threshold for preemption and remote IPIs.
*/
static int sched_interact = SCHED_INTERACT_THRESH;
static int tickincr = 8 << SCHED_TICK_SHIFT;
static int realstathz = 127; /* reset during boot. */
static int sched_slice = 10; /* reset during boot. */
static int sched_slice_min = 1; /* reset during boot. */
#ifdef PREEMPTION
#ifdef FULL_PREEMPTION
static int preempt_thresh = PRI_MAX_IDLE;
#else
static int preempt_thresh = PRI_MIN_KERN;
#endif
#else
static int preempt_thresh = 0;
#endif
static int static_boost = PRI_MIN_BATCH;
static int sched_idlespins = 10000;
static int sched_idlespinthresh = -1;
/*
* 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();
*/
struct tdq {
/*
* Ordered to improve efficiency of cpu_search() and switch().
* tdq_lock is padded to avoid false sharing with tdq_load and
* tdq_cpu_idle.
*/
struct mtx_padalign tdq_lock; /* run queue lock. */
struct cpu_group *tdq_cg; /* Pointer to cpu topology. */
volatile int tdq_load; /* Aggregate load. */
volatile int tdq_cpu_idle; /* cpu_idle() is active. */
int tdq_sysload; /* For loadavg, !ITHD load. */
int tdq_transferable; /* Transferable thread count. */
short tdq_switchcnt; /* Switches this tick. */
short tdq_oldswitchcnt; /* Switches last tick. */
u_char tdq_lowpri; /* Lowest priority thread. */
u_char tdq_ipipending; /* IPI pending. */
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. */
char tdq_name[TDQ_NAME_LEN];
#ifdef KTR
char tdq_loadname[TDQ_LOADNAME_LEN];
#endif
} __aligned(64);
/* Idle thread states and config. */
#define TDQ_RUNNING 1
#define TDQ_IDLE 2
#ifdef SMP
struct cpu_group *cpu_top; /* CPU topology */
#define SCHED_AFFINITY_DEFAULT (max(1, hz / 1000))
#define SCHED_AFFINITY(ts, t) ((ts)->ts_rltick > ticks - ((t) * affinity))
/*
* Run-time tunables.
*/
static int rebalance = 1;
static int balance_interval = 128; /* Default set in sched_initticks(). */
static int affinity;
static int steal_idle = 1;
static int steal_thresh = 2;
/*
* One thread queue per processor.
*/
static struct tdq tdq_cpu[MAXCPU];
static struct tdq *balance_tdq;
static int balance_ticks;
static DPCPU_DEFINE(uint32_t, randomval);
#define TDQ_SELF() (&tdq_cpu[PCPU_GET(cpuid)])
#define TDQ_CPU(x) (&tdq_cpu[(x)])
#define TDQ_ID(x) ((int)((x) - tdq_cpu))
#else /* !SMP */
static struct tdq tdq_cpu;
#define TDQ_ID(x) (0)
#define TDQ_SELF() (&tdq_cpu)
#define TDQ_CPU(x) (&tdq_cpu)
#endif
#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)))
#define TDQ_LOCKPTR(t) ((struct mtx *)(&(t)->tdq_lock))
static void sched_priority(struct thread *);
static void sched_thread_priority(struct thread *, u_char);
static int sched_interact_score(struct thread *);
static void sched_interact_update(struct thread *);
static void sched_interact_fork(struct thread *);
static void sched_pctcpu_update(struct td_sched *, int);
/* Operations on per processor queues */
static struct thread *tdq_choose(struct tdq *);
static void tdq_setup(struct tdq *);
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 *);
static inline int sched_shouldpreempt(int, int, int);
void tdq_print(int cpu);
static void runq_print(struct runq *rq);
static void tdq_add(struct tdq *, struct thread *, int);
#ifdef SMP
static int tdq_move(struct tdq *, struct tdq *);
static int tdq_idled(struct tdq *);
static void tdq_notify(struct tdq *, struct thread *);
static struct thread *tdq_steal(struct tdq *, int);
static struct thread *runq_steal(struct runq *, int);
static int sched_pickcpu(struct thread *, int);
static void sched_balance(void);
static int sched_balance_pair(struct tdq *, struct tdq *);
static inline struct tdq *sched_setcpu(struct thread *, int, int);
static inline void thread_unblock_switch(struct thread *, struct mtx *);
static struct mtx *sched_switch_migrate(struct tdq *, struct thread *, int);
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);
#endif
static void sched_setup(void *dummy);
SYSINIT(sched_setup, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, sched_setup, NULL);
static void sched_initticks(void *dummy);
SYSINIT(sched_initticks, SI_SUB_CLOCKS, SI_ORDER_THIRD, sched_initticks,
NULL);
SDT_PROVIDER_DEFINE(sched);
SDT_PROBE_DEFINE3(sched, , , change__pri, "struct thread *",
"struct proc *", "uint8_t");
SDT_PROBE_DEFINE3(sched, , , dequeue, "struct thread *",
"struct proc *", "void *");
SDT_PROBE_DEFINE4(sched, , , enqueue, "struct thread *",
"struct proc *", "void *", "int");
SDT_PROBE_DEFINE4(sched, , , lend__pri, "struct thread *",
"struct proc *", "uint8_t", "struct thread *");
SDT_PROBE_DEFINE2(sched, , , load__change, "int", "int");
SDT_PROBE_DEFINE2(sched, , , off__cpu, "struct thread *",
"struct proc *");
SDT_PROBE_DEFINE(sched, , , on__cpu);
SDT_PROBE_DEFINE(sched, , , remain__cpu);
SDT_PROBE_DEFINE2(sched, , , surrender, "struct thread *",
"struct proc *");
/*
* Print the threads waiting on a run-queue.
*/
static void
runq_print(struct runq *rq)
{
struct rqhead *rqh;
struct thread *td;
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];
TAILQ_FOREACH(td, rqh, td_runq) {
printf("\t\t\ttd %p(%s) priority %d rqindex %d pri %d\n",
td, td->td_name, td->td_priority,
td->td_rqindex, pri);
}
}
}
}
/*
* Print the status of a per-cpu thread queue. Should be a ddb show cmd.
*/
void
tdq_print(int cpu)
{
struct tdq *tdq;
tdq = TDQ_CPU(cpu);
printf("tdq %d:\n", TDQ_ID(tdq));
printf("\tlock %p\n", TDQ_LOCKPTR(tdq));
printf("\tLock name: %s\n", tdq->tdq_name);
printf("\tload: %d\n", tdq->tdq_load);
printf("\tswitch cnt: %d\n", tdq->tdq_switchcnt);
printf("\told switch cnt: %d\n", tdq->tdq_oldswitchcnt);
printf("\ttimeshare idx: %d\n", tdq->tdq_idx);
printf("\ttimeshare ridx: %d\n", tdq->tdq_ridx);
printf("\tload transferable: %d\n", tdq->tdq_transferable);
printf("\tlowest priority: %d\n", tdq->tdq_lowpri);
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);
}
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);
/*
* If we're interactive or better and there is non-interactive
* or worse running preempt only remote processors.
*/
if (remote && pri <= PRI_MAX_INTERACT && cpri > PRI_MAX_INTERACT)
return (1);
return (0);
}
/*
* 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.
*/
static __inline void
tdq_runq_add(struct tdq *tdq, struct thread *td, int flags)
{
struct td_sched *ts;
u_char pri;
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
THREAD_LOCK_ASSERT(td, MA_OWNED);
pri = td->td_priority;
ts = td->td_sched;
TD_SET_RUNQ(td);
if (THREAD_CAN_MIGRATE(td)) {
tdq->tdq_transferable++;
ts->ts_flags |= TSF_XFERABLE;
}
if (pri < PRI_MIN_BATCH) {
ts->ts_runq = &tdq->tdq_realtime;
} else if (pri <= PRI_MAX_BATCH) {
ts->ts_runq = &tdq->tdq_timeshare;
KASSERT(pri <= PRI_MAX_BATCH && pri >= PRI_MIN_BATCH,
("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.
*/
if ((flags & (SRQ_BORROWING|SRQ_PREEMPTED)) == 0) {
pri = RQ_NQS * (pri - PRI_MIN_BATCH) / PRI_BATCH_RANGE;
pri = (pri + tdq->tdq_idx) % RQ_NQS;
/*
* 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)
pri = (unsigned char)(pri - 1) % RQ_NQS;
} else
pri = tdq->tdq_ridx;
runq_add_pri(ts->ts_runq, td, pri, flags);
return;
} else
ts->ts_runq = &tdq->tdq_idle;
runq_add(ts->ts_runq, td, flags);
}
/*
* 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.
*/
static __inline void
tdq_runq_rem(struct tdq *tdq, struct thread *td)
{
struct td_sched *ts;
ts = td->td_sched;
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
KASSERT(ts->ts_runq != NULL,
("tdq_runq_remove: thread %p null ts_runq", td));
if (ts->ts_flags & TSF_XFERABLE) {
tdq->tdq_transferable--;
ts->ts_flags &= ~TSF_XFERABLE;
}
if (ts->ts_runq == &tdq->tdq_timeshare) {
if (tdq->tdq_idx != tdq->tdq_ridx)
runq_remove_idx(ts->ts_runq, td, &tdq->tdq_ridx);
else
runq_remove_idx(ts->ts_runq, td, NULL);
} else
runq_remove(ts->ts_runq, td);
}
/*
* Load is maintained for all threads RUNNING and ON_RUNQ. Add the load
* for this thread to the referenced thread queue.
*/
static void
tdq_load_add(struct tdq *tdq, struct thread *td)
{
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
THREAD_LOCK_ASSERT(td, MA_OWNED);
tdq->tdq_load++;
if ((td->td_flags & TDF_NOLOAD) == 0)
tdq->tdq_sysload++;
KTR_COUNTER0(KTR_SCHED, "load", tdq->tdq_loadname, tdq->tdq_load);
SDT_PROBE2(sched, , , load__change, (int)TDQ_ID(tdq), tdq->tdq_load);
}
/*
* Remove the load from a thread that is transitioning to a sleep state or
* exiting.
*/
static void
tdq_load_rem(struct tdq *tdq, struct thread *td)
{
THREAD_LOCK_ASSERT(td, MA_OWNED);
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
KASSERT(tdq->tdq_load != 0,
("tdq_load_rem: Removing with 0 load on queue %d", TDQ_ID(tdq)));
tdq->tdq_load--;
if ((td->td_flags & TDF_NOLOAD) == 0)
tdq->tdq_sysload--;
KTR_COUNTER0(KTR_SCHED, "load", tdq->tdq_loadname, tdq->tdq_load);
SDT_PROBE2(sched, , , load__change, (int)TDQ_ID(tdq), tdq->tdq_load);
}
/*
* 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);
}
/*
* 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;
td = tdq_choose(tdq);
if (td == NULL || td->td_priority > ctd->td_priority)
tdq->tdq_lowpri = ctd->td_priority;
else
tdq->tdq_lowpri = td->td_priority;
}
#ifdef SMP
struct cpu_search {
cpuset_t cs_mask;
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;
};
#define CPU_SEARCH_LOWEST 0x1
#define CPU_SEARCH_HIGHEST 0x2
#define CPU_SEARCH_BOTH (CPU_SEARCH_LOWEST|CPU_SEARCH_HIGHEST)
#define CPUSET_FOREACH(cpu, mask) \
for ((cpu) = 0; (cpu) <= mp_maxid; (cpu)++) \
if (CPU_ISSET(cpu, &mask))
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,
struct cpu_search *high);
int __noinline cpu_search_both(const struct cpu_group *cg,
struct cpu_search *low, struct cpu_search *high);
/*
* 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
* the system. This balances work among caches and busses.
*
* 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.
*/
static __always_inline int
cpu_search(const struct cpu_group *cg, struct cpu_search *low,
struct cpu_search *high, const int match)
{
struct cpu_search lgroup;
struct cpu_search hgroup;
cpuset_t cpumask;
struct cpu_group *child;
struct tdq *tdq;
int cpu, i, hload, lload, load, total, rnd, *rndptr;
total = 0;
cpumask = cg->cg_mask;
if (match & CPU_SEARCH_LOWEST) {
lload = INT_MAX;
lgroup = *low;
}
if (match & CPU_SEARCH_HIGHEST) {
hload = INT_MIN;
hgroup = *high;
}
/* Iterate through the child CPU groups and then remaining CPUs. */
for (i = cg->cg_children, cpu = mp_maxid; ; ) {
if (i == 0) {
#ifdef HAVE_INLINE_FFSL
cpu = CPU_FFS(&cpumask) - 1;
#else
while (cpu >= 0 && !CPU_ISSET(cpu, &cpumask))
cpu--;
#endif
if (cpu < 0)
break;
child = NULL;
} else
child = &cg->cg_child[i - 1];
if (match & CPU_SEARCH_LOWEST)
lgroup.cs_cpu = -1;
if (match & CPU_SEARCH_HIGHEST)
hgroup.cs_cpu = -1;
if (child) { /* Handle child CPU group. */
CPU_NAND(&cpumask, &child->cg_mask);
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;
}
} else { /* Handle child CPU. */
CPU_CLR(cpu, &cpumask);
tdq = TDQ_CPU(cpu);
load = tdq->tdq_load * 256;
rndptr = DPCPU_PTR(randomval);
rnd = (*rndptr = *rndptr * 69069 + 5) >> 26;
if (match & CPU_SEARCH_LOWEST) {
if (cpu == low->cs_prefer)
load -= 64;
/* If that CPU is allowed and get data. */
if (tdq->tdq_lowpri > lgroup.cs_pri &&
tdq->tdq_load <= lgroup.cs_limit &&
CPU_ISSET(cpu, &lgroup.cs_mask)) {
lgroup.cs_cpu = cpu;
lgroup.cs_load = load - rnd;
}
}
if (match & CPU_SEARCH_HIGHEST)
if (tdq->tdq_load >= hgroup.cs_limit &&
tdq->tdq_transferable &&
CPU_ISSET(cpu, &hgroup.cs_mask)) {
hgroup.cs_cpu = cpu;
hgroup.cs_load = load - rnd;
}
}
total += load;
/* We have info about child item. Compare it. */
if (match & CPU_SEARCH_LOWEST) {
if (lgroup.cs_cpu >= 0 &&
(load < lload ||
(load == lload && lgroup.cs_load < low->cs_load))) {
lload = load;
low->cs_cpu = lgroup.cs_cpu;
low->cs_load = lgroup.cs_load;
}
}
if (match & CPU_SEARCH_HIGHEST)
if (hgroup.cs_cpu >= 0 &&
(load > hload ||
(load == hload && hgroup.cs_load > high->cs_load))) {
hload = load;
high->cs_cpu = hgroup.cs_cpu;
high->cs_load = hgroup.cs_load;
}
if (child) {
i--;
if (i == 0 && CPU_EMPTY(&cpumask))
break;
}
#ifndef HAVE_INLINE_FFSL
else
cpu--;
#endif
}
return (total);
}
/*
* cpu_search instantiations must pass constants to maintain the inline
* optimization.
*/
int
cpu_search_lowest(const struct cpu_group *cg, struct cpu_search *low)
{
return cpu_search(cg, low, NULL, CPU_SEARCH_LOWEST);
}
int
cpu_search_highest(const struct cpu_group *cg, struct cpu_search *high)
{
return cpu_search(cg, NULL, high, CPU_SEARCH_HIGHEST);
}
int
cpu_search_both(const struct cpu_group *cg, struct cpu_search *low,
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
sched_lowest(const struct cpu_group *cg, cpuset_t mask, int pri, int maxload,
int prefer)
{
struct cpu_search low;
low.cs_cpu = -1;
low.cs_prefer = prefer;
low.cs_mask = mask;
low.cs_pri = pri;
low.cs_limit = maxload;
cpu_search_lowest(cg, &low);
return low.cs_cpu;
}
/*
* Find the cpu with the highest load via the highest loaded path.
*/
static inline int
sched_highest(const struct cpu_group *cg, cpuset_t mask, int minload)
{
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;
}
static void
sched_balance_group(struct cpu_group *cg)
{
cpuset_t hmask, lmask;
int high, low, anylow;
CPU_FILL(&hmask);
for (;;) {
high = sched_highest(cg, hmask, 1);
/* Stop if there is no more CPU with transferrable threads. */
if (high == -1)
break;
CPU_CLR(high, &hmask);
CPU_COPY(&hmask, &lmask);
/* Stop if there is no more CPU left for low. */
if (CPU_EMPTY(&lmask))
break;
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;
}
}
}
static void
sched_balance(void)
{
struct tdq *tdq;
/*
* Select a random time between .5 * balance_interval and
* 1.5 * balance_interval.
*/
balance_ticks = max(balance_interval / 2, 1);
balance_ticks += random() % balance_interval;
if (smp_started == 0 || rebalance == 0)
return;
tdq = TDQ_SELF();
TDQ_UNLOCK(tdq);
sched_balance_group(cpu_top);
TDQ_LOCK(tdq);
}
/*
* 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);
}
}
/*
* 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);
}
/*
* Transfer load between two imbalanced thread queues.
*/
static int
sched_balance_pair(struct tdq *high, struct tdq *low)
{
int moved;
int cpu;
tdq_lock_pair(high, low);
moved = 0;
/*
* Determine what the imbalance is and then adjust that to how many
* threads we actually have to give up (transferable).
*/
if (high->tdq_transferable != 0 && high->tdq_load > low->tdq_load &&
(moved = tdq_move(high, low)) > 0) {
/*
* In case the target isn't the current cpu IPI it to force a
* reschedule with the new workload.
*/
cpu = TDQ_ID(low);
if (cpu != PCPU_GET(cpuid))
ipi_cpu(cpu, IPI_PREEMPT);
}
tdq_unlock_pair(high, low);
return (moved);
}
/*
* Move a thread from one thread queue to another.
*/
static int
tdq_move(struct tdq *from, struct tdq *to)
{
struct td_sched *ts;
struct thread *td;
struct tdq *tdq;
int cpu;
TDQ_LOCK_ASSERT(from, MA_OWNED);
TDQ_LOCK_ASSERT(to, MA_OWNED);
tdq = from;
cpu = TDQ_ID(to);
td = tdq_steal(tdq, cpu);
if (td == NULL)
return (0);
ts = td->td_sched;
/*
* Although the run queue is locked the thread may be blocked. Lock
* it to clear this and acquire the run-queue lock.
*/
thread_lock(td);
/* Drop recursive lock on from acquired via thread_lock(). */
TDQ_UNLOCK(from);
sched_rem(td);
ts->ts_cpu = cpu;
td->td_lock = TDQ_LOCKPTR(to);
tdq_add(to, td, SRQ_YIELDING);
return (1);
}
/*
* This tdq has idled. Try to steal a thread from another cpu and switch
* to it.
*/
static int
tdq_idled(struct tdq *tdq)
{
struct cpu_group *cg;
struct tdq *steal;
cpuset_t mask;
int thresh;
int cpu;
if (smp_started == 0 || steal_idle == 0)
return (1);
CPU_FILL(&mask);
CPU_CLR(PCPU_GET(cpuid), &mask);
/* We don't want to be preempted while we're iterating. */
spinlock_enter();
for (cg = tdq->tdq_cg; cg != NULL; ) {
if ((cg->cg_flags & CG_FLAG_THREAD) == 0)
thresh = steal_thresh;
else
thresh = 1;
cpu = sched_highest(cg, mask, thresh);
if (cpu == -1) {
cg = cg->cg_parent;
continue;
}
steal = TDQ_CPU(cpu);
CPU_CLR(cpu, &mask);
tdq_lock_pair(tdq, steal);
if (steal->tdq_load < thresh || steal->tdq_transferable == 0) {
tdq_unlock_pair(tdq, steal);
continue;
}
/*
* If a thread was added while interrupts were disabled don't
* steal one here. If we fail to acquire one due to affinity
* restrictions loop again with this cpu removed from the
* set.
*/
if (tdq->tdq_load == 0 && tdq_move(steal, tdq) == 0) {
tdq_unlock_pair(tdq, steal);
continue;
}
spinlock_exit();
TDQ_UNLOCK(steal);
mi_switch(SW_VOL | SWT_IDLE, NULL);
thread_unlock(curthread);
return (0);
}
spinlock_exit();
return (1);
}
/*
* Notify a remote cpu of new work. Sends an IPI if criteria are met.
*/
static void
tdq_notify(struct tdq *tdq, struct thread *td)
{
struct thread *ctd;
int pri;
int cpu;
if (tdq->tdq_ipipending)
return;
cpu = td->td_sched->ts_cpu;
pri = td->td_priority;
ctd = pcpu_find(cpu)->pc_curthread;
if (!sched_shouldpreempt(pri, ctd->td_priority, 1))
return;
/*
* Make sure that our caller's earlier update to tdq_load is
* globally visible before we read tdq_cpu_idle. Idle thread
* accesses both of them without locks, and the order is important.
*/
mb();
if (TD_IS_IDLETHREAD(ctd)) {
/*
* If the MD code has an idle wakeup routine try that before
* falling back to IPI.
*/
if (!tdq->tdq_cpu_idle || cpu_idle_wakeup(cpu))
return;
}
tdq->tdq_ipipending = 1;
ipi_cpu(cpu, IPI_PREEMPT);
}
/*
* Steals load from a timeshare queue. Honors the rotating queue head
* index.
*/
static struct thread *
runq_steal_from(struct runq *rq, int cpu, u_char start)
{
struct rqbits *rqb;
struct rqhead *rqh;
struct thread *td, *first;
int bit;
int i;
rqb = &rq->rq_status;
bit = start & (RQB_BPW -1);
first = NULL;
again:
for (i = RQB_WORD(start); i < RQB_LEN; bit = 0, i++) {
if (rqb->rqb_bits[i] == 0)
continue;
if (bit == 0)
bit = RQB_FFS(rqb->rqb_bits[i]);
for (; bit < RQB_BPW; bit++) {
if ((rqb->rqb_bits[i] & (1ul << bit)) == 0)
continue;
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;
}
}
}
if (start != 0) {
start = 0;
goto again;
}
if (first && THREAD_CAN_MIGRATE(first) &&
THREAD_CAN_SCHED(first, cpu))
return (first);
return (NULL);
}
/*
* Steals load from a standard linear queue.
*/
static struct thread *
runq_steal(struct runq *rq, int cpu)
{
struct rqhead *rqh;
struct rqbits *rqb;
struct thread *td;
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++) {
if ((rqb->rqb_bits[word] & (1ul << bit)) == 0)
continue;
rqh = &rq->rq_queues[bit + (word << RQB_L2BPW)];
TAILQ_FOREACH(td, rqh, td_runq)
if (THREAD_CAN_MIGRATE(td) &&
THREAD_CAN_SCHED(td, cpu))
return (td);
}
}
return (NULL);
}
/*
* Attempt to steal a thread in priority order from a thread queue.
*/
static struct thread *
tdq_steal(struct tdq *tdq, int cpu)
{
struct thread *td;
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
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);
return (runq_steal(&tdq->tdq_idle, cpu));
}
/*
* Sets the thread lock and ts_cpu to match the requested cpu. Unlocks the
* current lock and returns with the assigned queue locked.
*/
static inline struct tdq *
sched_setcpu(struct thread *td, int cpu, int flags)
{
struct tdq *tdq;
THREAD_LOCK_ASSERT(td, MA_OWNED);
tdq = TDQ_CPU(cpu);
td->td_sched->ts_cpu = cpu;
/*
* If the lock matches just return the queue.
*/
if (td->td_lock == TDQ_LOCKPTR(tdq))
return (tdq);
#ifdef notyet
/*
* If the thread isn't running its lockptr is a
* turnstile or a sleepqueue. We can just lock_set without
* blocking.
*/
if (TD_CAN_RUN(td)) {
TDQ_LOCK(tdq);
thread_lock_set(td, TDQ_LOCKPTR(tdq));
return (tdq);
}
#endif
/*
* The hard case, migration, we need to block the thread first to
* prevent order reversals with other cpus locks.
*/
spinlock_enter();
thread_lock_block(td);
TDQ_LOCK(tdq);
thread_lock_unblock(td, TDQ_LOCKPTR(tdq));
spinlock_exit();
return (tdq);
}
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");
static int
sched_pickcpu(struct thread *td, int flags)
{
struct cpu_group *cg, *ccg;
struct td_sched *ts;
struct tdq *tdq;
cpuset_t mask;
int cpu, pri, self;
self = PCPU_GET(cpuid);
ts = td->td_sched;
if (smp_started == 0)
return (self);
/*
* Don't migrate a running thread from sched_switch().
*/
if ((flags & SRQ_OURSELF) || !THREAD_CAN_MIGRATE(td))
return (ts->ts_cpu);
/*
* Prefer to run interrupt threads on the processors that generate
* the interrupt.
*/
pri = td->td_priority;
if (td->td_priority <= PRI_MAX_ITHD && THREAD_CAN_SCHED(td, self) &&
curthread->td_intr_nesting_level && ts->ts_cpu != self) {
SCHED_STAT_INC(pickcpu_intrbind);
ts->ts_cpu = self;
if (TDQ_CPU(self)->tdq_lowpri > pri) {
SCHED_STAT_INC(pickcpu_affinity);
return (ts->ts_cpu);
}
}
/*
* If the thread can run on the last cpu and the affinity has not
* expired or it is idle run it there.
*/
tdq = TDQ_CPU(ts->ts_cpu);
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) {
SCHED_STAT_INC(pickcpu_idle_affinity);
return (ts->ts_cpu);
}
}
/*
* 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.
*/
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;
cpu = -1;
/* Search the group for the less loaded idle CPU we can run now. */
mask = td->td_cpuset->cs_mask;
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. */
if (cpu == -1)
cpu = sched_lowest(cpu_top, mask, -1, INT_MAX, ts->ts_cpu);
KASSERT(cpu != -1, ("sched_pickcpu: Failed to find a cpu."));
/*
* Compare the lowest loaded cpu to current cpu.
*/
if (THREAD_CAN_SCHED(td, self) && TDQ_CPU(self)->tdq_lowpri > pri &&
TDQ_CPU(cpu)->tdq_lowpri < PRI_MIN_IDLE &&
TDQ_CPU(self)->tdq_load <= TDQ_CPU(cpu)->tdq_load + 1) {
SCHED_STAT_INC(pickcpu_local);
cpu = self;
} else
SCHED_STAT_INC(pickcpu_lowest);
if (cpu != ts->ts_cpu)
SCHED_STAT_INC(pickcpu_migration);
return (cpu);
}
#endif
/*
* Pick the highest priority task we have and return it.
*/
static struct thread *
tdq_choose(struct tdq *tdq)
{
struct thread *td;
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
td = runq_choose(&tdq->tdq_realtime);
if (td != NULL)
return (td);
td = runq_choose_from(&tdq->tdq_timeshare, tdq->tdq_ridx);
if (td != NULL) {
KASSERT(td->td_priority >= PRI_MIN_BATCH,
("tdq_choose: Invalid priority on timeshare queue %d",
td->td_priority));
return (td);
}
td = runq_choose(&tdq->tdq_idle);
if (td != NULL) {
KASSERT(td->td_priority >= PRI_MIN_IDLE,
("tdq_choose: Invalid priority on idle queue %d",
td->td_priority));
return (td);
}
return (NULL);
}
/*
* Initialize a thread queue.
*/
static void
tdq_setup(struct tdq *tdq)
{
if (bootverbose)
printf("ULE: setup cpu %d\n", TDQ_ID(tdq));
runq_init(&tdq->tdq_realtime);
runq_init(&tdq->tdq_timeshare);
runq_init(&tdq->tdq_idle);
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",
MTX_SPIN | MTX_RECURSE);
#ifdef KTR
snprintf(tdq->tdq_loadname, sizeof(tdq->tdq_loadname),
"CPU %d load", (int)TDQ_ID(tdq));
#endif
}
#ifdef SMP
static void
sched_setup_smp(void)
{
struct tdq *tdq;
int i;
cpu_top = smp_topo();
CPU_FOREACH(i) {
tdq = TDQ_CPU(i);
tdq_setup(tdq);
tdq->tdq_cg = smp_topo_find(cpu_top, i);
if (tdq->tdq_cg == NULL)
panic("Can't find cpu group for %d\n", i);
}
balance_tdq = TDQ_SELF();
sched_balance();
}
#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
sched_setup_smp();
#else
tdq_setup(tdq);
#endif
/* Add thread0's load since it's running. */
TDQ_LOCK(tdq);
thread0.td_lock = TDQ_LOCKPTR(TDQ_SELF());
tdq_load_add(tdq, &thread0);
tdq->tdq_lowpri = thread0.td_priority;
TDQ_UNLOCK(tdq);
}
/*
* This routine determines time constants after stathz and hz are setup.
*/
/* ARGSUSED */
static void
sched_initticks(void *dummy)
{
int incr;
realstathz = stathz ? stathz : hz;
sched_slice = realstathz / SCHED_SLICE_DEFAULT_DIVISOR;
sched_slice_min = sched_slice / SCHED_SLICE_MIN_DIVISOR;
hogticks = imax(1, (2 * hz * sched_slice + realstathz / 2) /
realstathz);
/*
* tickincr is shifted out by 10 to avoid rounding errors due to
* hz not being evenly divisible by stathz on all platforms.
*/
incr = (hz << SCHED_TICK_SHIFT) / realstathz;
/*
* This does not work for values of stathz that are more than
* 1 << SCHED_TICK_SHIFT * hz. In practice this does not happen.
*/
if (incr == 0)
incr = 1;
tickincr = incr;
#ifdef SMP
/*
* Set the default balance interval now that we know
* what realstathz is.
*/
balance_interval = realstathz;
affinity = SCHED_AFFINITY_DEFAULT;
#endif
if (sched_idlespinthresh < 0)
sched_idlespinthresh = 2 * max(10000, 6 * hz) / realstathz;
}
/*
* 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.
*/
static int
sched_interact_score(struct thread *td)
{
struct td_sched *ts;
int div;
ts = td->td_sched;
/*
* 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);
}
/*
* Scale the scheduling priority according to the "interactivity" of this
* process.
*/
static void
sched_priority(struct thread *td)
{
int score;
int pri;
if (PRI_BASE(td->td_pri_class) != PRI_TIMESHARE)
return;
/*
* 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.
*
* Scores greater than this are placed on the normal timeshare queue
* where the priority is partially decided by the most recent cpu
* utilization and the rest is decided by nice value.
*
* 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.
*/
score = imax(0, sched_interact_score(td) + td->td_proc->p_nice);
if (score < sched_interact) {
pri = PRI_MIN_INTERACT;
pri += ((PRI_MAX_INTERACT - PRI_MIN_INTERACT + 1) /
sched_interact) * score;
KASSERT(pri >= PRI_MIN_INTERACT && pri <= PRI_MAX_INTERACT,
("sched_priority: invalid interactive priority %d score %d",
pri, score));
} else {
pri = SCHED_PRI_MIN;
if (td->td_sched->ts_ticks)
pri += min(SCHED_PRI_TICKS(td->td_sched),
SCHED_PRI_RANGE - 1);
pri += SCHED_PRI_NICE(td->td_proc->p_nice);
KASSERT(pri >= PRI_MIN_BATCH && pri <= PRI_MAX_BATCH,
("sched_priority: invalid priority %d: nice %d, "
"ticks %d ftick %d ltick %d tick pri %d",
pri, td->td_proc->p_nice, td->td_sched->ts_ticks,
td->td_sched->ts_ftick, td->td_sched->ts_ltick,
SCHED_PRI_TICKS(td->td_sched)));
}
sched_user_prio(td, pri);
return;
}
/*
* This routine enforces a maximum limit on the amount of scheduling history
* kept. It is called after either the slptime or runtime is adjusted. This
* function is ugly due to integer math.
*/
static void
sched_interact_update(struct thread *td)
{
struct td_sched *ts;
u_int sum;
ts = td->td_sched;
sum = ts->ts_runtime + ts->ts_slptime;
if (sum < SCHED_SLP_RUN_MAX)
return;
/*
* 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) {
if (ts->ts_runtime > ts->ts_slptime) {
ts->ts_runtime = SCHED_SLP_RUN_MAX;
ts->ts_slptime = 1;
} else {
ts->ts_slptime = SCHED_SLP_RUN_MAX;
ts->ts_runtime = 1;
}
return;
}
/*
* 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
* us into the range of [4/5 * SCHED_INTERACT_MAX, SCHED_INTERACT_MAX]
*/
if (sum > (SCHED_SLP_RUN_MAX / 5) * 6) {
ts->ts_runtime /= 2;
ts->ts_slptime /= 2;
return;
}
ts->ts_runtime = (ts->ts_runtime / 5) * 4;
ts->ts_slptime = (ts->ts_slptime / 5) * 4;
}
/*
* 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.
*/
static void
sched_interact_fork(struct thread *td)
{
int ratio;
int sum;
sum = td->td_sched->ts_runtime + td->td_sched->ts_slptime;
if (sum > SCHED_SLP_RUN_FORK) {
ratio = sum / SCHED_SLP_RUN_FORK;
td->td_sched->ts_runtime /= ratio;
td->td_sched->ts_slptime /= ratio;
}
}
/*
* Called from proc0_init() to setup the scheduler fields.
*/
void
schedinit(void)
{
/*
* Set up the scheduler specific parts of proc0.
*/
proc0.p_sched = NULL; /* XXX */
thread0.td_sched = &td_sched0;
td_sched0.ts_ltick = ticks;
td_sched0.ts_ftick = ticks;
td_sched0.ts_slice = 0;
}
/*
* This is only somewhat accurate since given many processes of the same
* priority they will switch when their slices run out, which will be
* at most sched_slice stathz ticks.
*/
int
sched_rr_interval(void)
{
/* Convert sched_slice from stathz to hz. */
return (imax(1, (sched_slice * hz + realstathz / 2) / realstathz));
}
/*
* 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.
*/
static void
sched_pctcpu_update(struct td_sched *ts, int run)
{
int t = ticks;
if (t - ts->ts_ltick >= SCHED_TICK_TARG) {
ts->ts_ticks = 0;
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;
}
/*
* 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.
*/
static void
sched_thread_priority(struct thread *td, u_char prio)
{
struct td_sched *ts;
struct tdq *tdq;
int oldpri;
KTR_POINT3(KTR_SCHED, "thread", sched_tdname(td), "prio",
"prio:%d", td->td_priority, "new prio:%d", prio,
KTR_ATTR_LINKED, sched_tdname(curthread));
SDT_PROBE3(sched, , , change__pri, td, td->td_proc, prio);
if (td != curthread && prio < td->td_priority) {
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));
SDT_PROBE4(sched, , , lend__pri, td, td->td_proc, prio,
curthread);
}
ts = td->td_sched;
THREAD_LOCK_ASSERT(td, MA_OWNED);
if (td->td_priority == prio)
return;
/*
* 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.
*/
if (TD_ON_RUNQ(td) && prio < td->td_priority) {
sched_rem(td);
td->td_priority = prio;
sched_add(td, SRQ_BORROWING);
return;
}
/*
* If the thread is currently running we may have to adjust the lowpri
* information so other cpus are aware of our current priority.
*/
if (TD_IS_RUNNING(td)) {
tdq = TDQ_CPU(ts->ts_cpu);
oldpri = td->td_priority;
td->td_priority = prio;
if (prio < tdq->tdq_lowpri)
tdq->tdq_lowpri = prio;
else if (tdq->tdq_lowpri == oldpri)
tdq_setlowpri(tdq, td);
return;
}
td->td_priority = prio;
}
/*
* 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)
base_pri = td->td_user_pri;
else
base_pri = td->td_base_pri;
if (prio >= base_pri) {
td->td_flags &= ~TDF_BORROWING;
sched_thread_priority(td, base_pri);
} else
sched_lend_prio(td, prio);
}
/*
* Standard entry for setting the priority to an absolute value.
*/
void
sched_prio(struct thread *td, u_char prio)
{
u_char oldprio;
/* First, update the base priority. */
td->td_base_pri = prio;
/*
* If the thread is borrowing another thread's priority, don't
* 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);
}
/*
* Set the base user priority, does not effect current running priority.
*/
void
sched_user_prio(struct thread *td, u_char prio)
{
td->td_base_user_pri = prio;
if (td->td_lend_user_pri <= prio)
return;
td->td_user_pri = prio;
}
void
sched_lend_user_prio(struct thread *td, u_char prio)
{
THREAD_LOCK_ASSERT(td, MA_OWNED);
td->td_lend_user_pri = prio;
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;
}
/*
* 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;
tdn = TDQ_CPU(td->td_sched->ts_cpu);
#ifdef SMP
tdq_load_rem(tdq, td);
/*
* 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();
thread_lock_block(td); /* This releases the lock on tdq. */
/*
* 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.
*/
tdq_lock_pair(tdn, tdq);
tdq_add(tdn, td, flags);
tdq_notify(tdn, td);
TDQ_UNLOCK(tdn);
spinlock_exit();
#endif
return (TDQ_LOCKPTR(tdn));
}
/*
* Variadic version of thread_lock_unblock() that does not assume td_lock
* is blocked.
*/
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.
*/
void
sched_switch(struct thread *td, struct thread *newtd, int flags)
{
struct tdq *tdq;
struct td_sched *ts;
struct mtx *mtx;
int srqflag;
int cpuid, preempted;
THREAD_LOCK_ASSERT(td, MA_OWNED);
KASSERT(newtd == NULL, ("sched_switch: Unsupported newtd argument"));
cpuid = PCPU_GET(cpuid);
tdq = TDQ_CPU(cpuid);
ts = td->td_sched;
mtx = td->td_lock;
sched_pctcpu_update(ts, 1);
ts->ts_rltick = ticks;
td->td_lastcpu = td->td_oncpu;
td->td_oncpu = NOCPU;
preempted = !((td->td_flags & TDF_SLICEEND) ||
(flags & SWT_RELINQUISH));
td->td_flags &= ~(TDF_NEEDRESCHED | TDF_SLICEEND);
td->td_owepreempt = 0;
if (!TD_IS_IDLETHREAD(td))
tdq->tdq_switchcnt++;
/*
* The lock pointer in an idle thread should never change. Reset it
* to CAN_RUN as well.
*/
if (TD_IS_IDLETHREAD(td)) {
MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
TD_SET_CAN_RUN(td);
} else if (TD_IS_RUNNING(td)) {
MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
srqflag = preempted ?
SRQ_OURSELF|SRQ_YIELDING|SRQ_PREEMPTED :
SRQ_OURSELF|SRQ_YIELDING;
#ifdef SMP
if (THREAD_CAN_MIGRATE(td) && !THREAD_CAN_SCHED(td, ts->ts_cpu))
ts->ts_cpu = sched_pickcpu(td, 0);
#endif
if (ts->ts_cpu == cpuid)
tdq_runq_add(tdq, td, srqflag);
else {
KASSERT(THREAD_CAN_MIGRATE(td) ||
(ts->ts_flags & TSF_BOUND) != 0,
("Thread %p shouldn't migrate", td));
mtx = sched_switch_migrate(tdq, td, srqflag);
}
} else {
/* This thread must be going to sleep. */
TDQ_LOCK(tdq);
mtx = thread_lock_block(td);
tdq_load_rem(tdq, td);
}
/*
* 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.
*/
if (td != newtd) {
#ifdef HWPMC_HOOKS
if (PMC_PROC_IS_USING_PMCS(td->td_proc))
PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT);
#endif
SDT_PROBE2(sched, , , off__cpu, newtd, newtd->td_proc);
lock_profile_release_lock(&TDQ_LOCKPTR(tdq)->lock_object);
TDQ_LOCKPTR(tdq)->mtx_lock = (uintptr_t)newtd;
sched_pctcpu_update(newtd->td_sched, 0);
#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
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);
lock_profile_obtain_lock_success(
&TDQ_LOCKPTR(tdq)->lock_object, 0, 0, __FILE__, __LINE__);
SDT_PROBE0(sched, , , on__cpu);
#ifdef HWPMC_HOOKS
if (PMC_PROC_IS_USING_PMCS(td->td_proc))
PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_IN);
#endif
} else {
thread_unblock_switch(td, mtx);
SDT_PROBE0(sched, , , remain__cpu);
}
/*
* Assert that all went well and return.
*/
TDQ_LOCK_ASSERT(tdq, MA_OWNED|MA_NOTRECURSED);
MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
td->td_oncpu = cpuid;
}
/*
* Adjust thread priorities as a result of a nice request.
*/
void
sched_nice(struct proc *p, int nice)
{
struct thread *td;
PROC_LOCK_ASSERT(p, MA_OWNED);
p->p_nice = nice;
FOREACH_THREAD_IN_PROC(p, td) {
thread_lock(td);
sched_priority(td);
sched_prio(td, td->td_base_user_pri);
thread_unlock(td);
}
}
/*
* Record the sleep time for the interactivity scorer.
*/
void
sched_sleep(struct thread *td, int prio)
{
THREAD_LOCK_ASSERT(td, MA_OWNED);
td->td_slptick = ticks;
if (TD_IS_SUSPENDED(td) || prio >= PSOCK)
td->td_flags |= TDF_CANSWAP;
if (PRI_BASE(td->td_pri_class) != PRI_TIMESHARE)
return;
if (static_boost == 1 && prio)
sched_prio(td, prio);
else if (static_boost && td->td_priority > static_boost)
sched_prio(td, static_boost);
}
/*
* Schedule a thread to resume execution and record how long it voluntarily
* slept. We also update the pctcpu, interactivity, and priority.
*/
void
sched_wakeup(struct thread *td)
{
struct td_sched *ts;
int slptick;
THREAD_LOCK_ASSERT(td, MA_OWNED);
ts = td->td_sched;
td->td_flags &= ~TDF_CANSWAP;
/*
* If we slept for more than a tick update our interactivity and
* priority.
*/
slptick = td->td_slptick;
td->td_slptick = 0;
if (slptick && slptick != ticks) {
ts->ts_slptime += (ticks - slptick) << SCHED_TICK_SHIFT;
sched_interact_update(td);
sched_pctcpu_update(ts, 0);
}
/*
* Reset the slice value since we slept and advanced the round-robin.
*/
ts->ts_slice = 0;
sched_add(td, SRQ_BORING);
}
/*
* Penalize the parent for creating a new child and initialize the child's
* priority.
*/
void
sched_fork(struct thread *td, struct thread *child)
{
THREAD_LOCK_ASSERT(td, MA_OWNED);
sched_pctcpu_update(td->td_sched, 1);
sched_fork_thread(td, child);
/*
* Penalize the parent and child for forking.
*/
sched_interact_fork(child);
sched_priority(child);
td->td_sched->ts_runtime += tickincr;
sched_interact_update(td);
sched_priority(td);
}
/*
* Fork a new thread, may be within the same process.
*/
void
sched_fork_thread(struct thread *td, struct thread *child)
{
struct td_sched *ts;
struct td_sched *ts2;
struct tdq *tdq;
tdq = TDQ_SELF();
THREAD_LOCK_ASSERT(td, MA_OWNED);
/*
* Initialize child.
*/
ts = td->td_sched;
ts2 = child->td_sched;
child->td_lock = TDQ_LOCKPTR(tdq);
child->td_cpuset = cpuset_ref(td->td_cpuset);
ts2->ts_cpu = ts->ts_cpu;
ts2->ts_flags = 0;
/*
* Grab our parents cpu estimation information.
*/
ts2->ts_ticks = ts->ts_ticks;
ts2->ts_ltick = ts->ts_ltick;
ts2->ts_ftick = ts->ts_ftick;
/*
* Do not inherit any borrowed priority from the parent.
*/
child->td_priority = child->td_base_pri;
/*
* And update interactivity score.
*/
ts2->ts_slptime = ts->ts_slptime;
ts2->ts_runtime = ts->ts_runtime;
/* Attempt to quickly learn interactivity. */
ts2->ts_slice = tdq_slice(tdq) - sched_slice_min;
#ifdef KTR
bzero(ts2->ts_name, sizeof(ts2->ts_name));
#endif
}
/*
* Adjust the priority class of a thread.
*/
void
sched_class(struct thread *td, int class)
{
THREAD_LOCK_ASSERT(td, MA_OWNED);
if (td->td_pri_class == class)
return;
td->td_pri_class = class;
}
/*
* Return some of the child's priority and interactivity to the parent.
*/
void
sched_exit(struct proc *p, struct thread *child)
{
struct thread *td;
KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "proc exit",
"prio:%d", child->td_priority);
PROC_LOCK_ASSERT(p, MA_OWNED);
td = FIRST_THREAD_IN_PROC(p);
sched_exit_thread(td, child);
}
/*
* 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.
*/
void
sched_exit_thread(struct thread *td, struct thread *child)
{
KTR_STATE1(KTR_SCHED, "thread", sched_tdname(child), "thread exit",
"prio:%d", child->td_priority);
/*
* 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.
*/
thread_lock(td);
td->td_sched->ts_runtime += child->td_sched->ts_runtime;
sched_interact_update(td);
sched_priority(td);
thread_unlock(td);
}
void
sched_preempt(struct thread *td)
{
struct tdq *tdq;
SDT_PROBE2(sched, , , surrender, td, td->td_proc);
thread_lock(td);
tdq = TDQ_SELF();
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
tdq->tdq_ipipending = 0;
if (td->td_priority > tdq->tdq_lowpri) {
int flags;
flags = SW_INVOL | SW_PREEMPT;
if (td->td_critnest > 1)
td->td_owepreempt = 1;
else if (TD_IS_IDLETHREAD(td))
mi_switch(flags | SWT_REMOTEWAKEIDLE, NULL);
else
mi_switch(flags | SWT_REMOTEPREEMPT, NULL);
}
thread_unlock(td);
}
/*
* Fix priorities on return to user-space. Priorities may be elevated due
* to static priorities in msleep() or similar.
*/
void
sched_userret(struct thread *td)
{
/*
* XXX we cheat slightly on the locking here to avoid locking in
* the usual case. Setting td_priority here is essentially an
* incomplete workaround for not setting it properly elsewhere.
* Now that some interrupt handlers are threads, not setting it
* properly elsewhere can clobber it in the window between setting
* it here and returning to user mode, so don't waste time setting
* it perfectly here.
*/
KASSERT((td->td_flags & TDF_BORROWING) == 0,
("thread with borrowed priority returning to userland"));
if (td->td_priority != td->td_user_pri) {
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);
}
}
/*
* Handle a stathz tick. This is really only relevant for timeshare
* threads.
*/
void
sched_clock(struct thread *td)
{
struct tdq *tdq;
struct td_sched *ts;
THREAD_LOCK_ASSERT(td, MA_OWNED);
tdq = TDQ_SELF();
#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
/*
* 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;
tdq->tdq_switchcnt = tdq->tdq_load;
/*
* Advance the insert index once for each tick to ensure that all
* threads get a chance to run.
*/
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;
}
ts = td->td_sched;
sched_pctcpu_update(ts, 1);
if (td->td_pri_class & PRI_FIFO_BIT)
return;
if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE) {
/*
* We used a tick; charge it to the thread so
* that we can compute our interactivity.
*/
td->td_sched->ts_runtime += tickincr;
sched_interact_update(td);
sched_priority(td);
}
/*
* Force a context switch if the current thread has used up a full
* time slice (default is 100ms).
*/
if (!TD_IS_IDLETHREAD(td) && ++ts->ts_slice >= tdq_slice(tdq)) {
ts->ts_slice = 0;
td->td_flags |= TDF_NEEDRESCHED | TDF_SLICEEND;
}
}
/*
* Called once per hz tick.
*/
void
sched_tick(int cnt)
{
}
/*
* Return whether the current CPU has runnable tasks. Used for in-kernel
* cooperative idle threads.
*/
int
sched_runnable(void)
{
struct tdq *tdq;
int load;
load = 1;
tdq = TDQ_SELF();
if ((curthread->td_flags & TDF_IDLETD) != 0) {
if (tdq->tdq_load > 0)
goto out;
} else
if (tdq->tdq_load - 1 > 0)
goto out;
load = 0;
out:
return (load);
}
/*
* 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.
*/
struct thread *
sched_choose(void)
{
struct thread *td;
struct tdq *tdq;
tdq = TDQ_SELF();
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
td = tdq_choose(tdq);
if (td) {
tdq_runq_rem(tdq, td);
tdq->tdq_lowpri = td->td_priority;
return (td);
}
tdq->tdq_lowpri = PRI_MAX_IDLE;
return (PCPU_GET(idlethread));
}
/*
* 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)
{
struct thread *ctd;
int cpri;
int pri;
THREAD_LOCK_ASSERT(curthread, MA_OWNED);
ctd = curthread;
pri = td->td_priority;
cpri = ctd->td_priority;
if (pri < cpri)
ctd->td_flags |= TDF_NEEDRESCHED;
if (panicstr != NULL || pri >= cpri || cold || TD_IS_INHIBITED(ctd))
return;
if (!sched_shouldpreempt(pri, cpri, 0))
return;
ctd->td_owepreempt = 1;
}
/*
* 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.
*/
void
tdq_add(struct tdq *tdq, struct thread *td, int flags)
{
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
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"));
KASSERT(td->td_flags & TDF_INMEM,
("sched_add: thread swapped out"));
if (td->td_priority < tdq->tdq_lowpri)
tdq->tdq_lowpri = td->td_priority;
tdq_runq_add(tdq, td, flags);
tdq_load_add(tdq, td);
}
/*
* 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;
#ifdef SMP
int cpu;
#endif
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));
SDT_PROBE4(sched, , , enqueue, td, td->td_proc, NULL,
flags & SRQ_PREEMPTED);
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.
*/
cpu = sched_pickcpu(td, flags);
tdq = sched_setcpu(td, cpu, flags);
tdq_add(tdq, td, flags);
if (cpu != PCPU_GET(cpuid)) {
tdq_notify(tdq, td);
return;
}
#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);
#endif
if (!(flags & SRQ_YIELDING))
sched_setpreempt(td);
}
/*
* 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.
*/
void
sched_rem(struct thread *td)
{
struct tdq *tdq;
KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "runq rem",
"prio:%d", td->td_priority);
SDT_PROBE3(sched, , , dequeue, td, td->td_proc, NULL);
tdq = TDQ_CPU(td->td_sched->ts_cpu);
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
KASSERT(TD_ON_RUNQ(td),
("sched_rem: thread not on run queue"));
tdq_runq_rem(tdq, td);
tdq_load_rem(tdq, td);
TD_SET_CAN_RUN(td);
if (td->td_priority == tdq->tdq_lowpri)
tdq_setlowpri(tdq, NULL);
}
/*
* Fetch cpu utilization information. Updates on demand.
*/
fixpt_t
sched_pctcpu(struct thread *td)
{
fixpt_t pctcpu;
struct td_sched *ts;
pctcpu = 0;
ts = td->td_sched;
if (ts == NULL)
return (0);
THREAD_LOCK_ASSERT(td, MA_OWNED);
sched_pctcpu_update(ts, TD_IS_RUNNING(td));
if (ts->ts_ticks) {
int rtick;
/* How many rtick per second ? */
rtick = min(SCHED_TICK_HZ(ts) / SCHED_TICK_SECS, hz);
pctcpu = (FSCALE * ((FSCALE * rtick)/hz)) >> FSHIFT;
}
return (pctcpu);
}
/*
* Enforce affinity settings for a thread. Called after adjustments to
* cpumask.
*/
void
sched_affinity(struct thread *td)
{
#ifdef SMP
struct td_sched *ts;
THREAD_LOCK_ASSERT(td, MA_OWNED);
ts = td->td_sched;
if (THREAD_CAN_SCHED(td, ts->ts_cpu))
return;
if (TD_ON_RUNQ(td)) {
sched_rem(td);
sched_add(td, SRQ_BORING);
return;
}
if (!TD_IS_RUNNING(td))
return;
/*
* Force a switch before returning to userspace. If the
* target thread is not running locally send an ipi to force
* the issue.
*/
td->td_flags |= TDF_NEEDRESCHED;
if (td != curthread)
ipi_cpu(ts->ts_cpu, IPI_PREEMPT);
#endif
}
/*
* Bind a thread to a target cpu.
*/
void
sched_bind(struct thread *td, int cpu)
{
struct td_sched *ts;
THREAD_LOCK_ASSERT(td, MA_OWNED|MA_NOTRECURSED);
KASSERT(td == curthread, ("sched_bind: can only bind curthread"));
ts = td->td_sched;
if (ts->ts_flags & TSF_BOUND)
sched_unbind(td);
KASSERT(THREAD_CAN_MIGRATE(td), ("%p must be migratable", td));
ts->ts_flags |= TSF_BOUND;
sched_pin();
if (PCPU_GET(cpuid) == cpu)
return;
ts->ts_cpu = cpu;
/* When we return from mi_switch we'll be on the correct cpu. */
mi_switch(SW_VOL, NULL);
}
/*
* Release a bound thread.
*/
void
sched_unbind(struct thread *td)
{
struct td_sched *ts;
THREAD_LOCK_ASSERT(td, MA_OWNED);
KASSERT(td == curthread, ("sched_unbind: can only bind curthread"));
ts = td->td_sched;
if ((ts->ts_flags & TSF_BOUND) == 0)
return;
ts->ts_flags &= ~TSF_BOUND;
sched_unpin();
}
int
sched_is_bound(struct thread *td)
{
THREAD_LOCK_ASSERT(td, MA_OWNED);
return (td->td_sched->ts_flags & TSF_BOUND);
}
/*
* Basic yield call.
*/
void
sched_relinquish(struct thread *td)
{
thread_lock(td);
mi_switch(SW_VOL | SWT_RELINQUISH, NULL);
thread_unlock(td);
}
/*
* Return the total system load.
*/
int
sched_load(void)
{
#ifdef SMP
int total;
int i;
total = 0;
CPU_FOREACH(i)
total += TDQ_CPU(i)->tdq_sysload;
return (total);
#else
return (TDQ_SELF()->tdq_sysload);
#endif
}
int
sched_sizeof_proc(void)
{
return (sizeof(struct proc));
}
int
sched_sizeof_thread(void)
{
return (sizeof(struct thread) + sizeof(struct td_sched));
}
#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
/*
* The actual idle process.
*/
void
sched_idletd(void *dummy)
{
struct thread *td;
struct tdq *tdq;
int oldswitchcnt, switchcnt;
int i;
mtx_assert(&Giant, MA_NOTOWNED);
td = curthread;
tdq = TDQ_SELF();
THREAD_NO_SLEEPING();
oldswitchcnt = -1;
for (;;) {
if (tdq->tdq_load) {
thread_lock(td);
mi_switch(SW_VOL | SWT_IDLE, NULL);
thread_unlock(td);
}
switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
#ifdef SMP
if (switchcnt != oldswitchcnt) {
oldswitchcnt = switchcnt;
if (tdq_idled(tdq) == 0)
continue;
}
switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
#else
oldswitchcnt = switchcnt;
#endif
/*
* If we're switching very frequently, spin while checking
* for load rather than entering a low power state that
* 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.
*/
if (TDQ_IDLESPIN(tdq) && switchcnt > sched_idlespinthresh) {
for (i = 0; i < sched_idlespins; i++) {
if (tdq->tdq_load)
break;
cpu_spinwait();
}
}
/* If there was context switch during spin, restart it. */
switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
if (tdq->tdq_load != 0 || switchcnt != oldswitchcnt)
continue;
/* Run main MD idle handler. */
tdq->tdq_cpu_idle = 1;
/*
* 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.
*/
mb();
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++;
}
}
/*
* A CPU is entering for the first time or a thread is exiting.
*/
void
sched_throw(struct thread *td)
{
struct thread *newtd;
struct tdq *tdq;
tdq = TDQ_SELF();
if (td == NULL) {
/* Correct spinlock nesting and acquire the correct lock. */
TDQ_LOCK(tdq);
spinlock_exit();
PCPU_SET(switchtime, cpu_ticks());
PCPU_SET(switchticks, ticks);
} else {
MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
tdq_load_rem(tdq, td);
lock_profile_release_lock(&TDQ_LOCKPTR(tdq)->lock_object);
}
KASSERT(curthread->td_md.md_spinlock_count == 1, ("invalid count"));
newtd = choosethread();
TDQ_LOCKPTR(tdq)->mtx_lock = (uintptr_t)newtd;
cpu_throw(td, newtd); /* doesn't return */
}
/*
* This is called from fork_exit(). Just acquire the correct locks and
* let fork do the rest of the work.
*/
void
sched_fork_exit(struct thread *td)
{
struct tdq *tdq;
int cpuid;
/*
* Finish setting up thread glue so that it begins execution in a
* non-nested critical section with the scheduler lock held.
*/
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;
TDQ_LOCK_ASSERT(tdq, MA_OWNED | MA_NOTRECURSED);
lock_profile_obtain_lock_success(
&TDQ_LOCKPTR(tdq)->lock_object, 0, 0, __FILE__, __LINE__);
}
/*
* Create on first use to catch odd startup conditons.
*/
char *
sched_tdname(struct thread *td)
{
#ifdef KTR
struct td_sched *ts;
ts = td->td_sched;
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
}
#ifdef KTR
void
sched_clear_tdname(struct thread *td)
{
struct td_sched *ts;
ts = td->td_sched;
ts->ts_name[0] = '\0';
}
#endif
#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)
{
char cpusetbuf[CPUSETBUFSIZ];
int i, first;
sbuf_printf(sb, "%*s<group level=\"%d\" cache-level=\"%d\">\n", indent,
"", 1 + indent / 2, cg->cg_level);
sbuf_printf(sb, "%*s <cpu count=\"%d\" mask=\"%s\">", indent, "",
cg->cg_count, cpusetobj_strprint(cpusetbuf, &cg->cg_mask));
first = TRUE;
for (i = 0; i < MAXCPU; i++) {
if (CPU_ISSET(i, &cg->cg_mask)) {
if (!first)
sbuf_printf(sb, ", ");
else
first = FALSE;
sbuf_printf(sb, "%d", i);
}
}
sbuf_printf(sb, "</cpu>\n");
if (cg->cg_flags != 0) {
sbuf_printf(sb, "%*s <flags>", indent, "");
if ((cg->cg_flags & CG_FLAG_HTT) != 0)
sbuf_printf(sb, "<flag name=\"HTT\">HTT group</flag>");
if ((cg->cg_flags & CG_FLAG_THREAD) != 0)
sbuf_printf(sb, "<flag name=\"THREAD\">THREAD group</flag>");
if ((cg->cg_flags & CG_FLAG_SMT) != 0)
sbuf_printf(sb, "<flag name=\"SMT\">SMT group</flag>");
sbuf_printf(sb, "</flags>\n");
}
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"));
topo = sbuf_new(NULL, NULL, 500, SBUF_AUTOEXTEND);
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) {
sbuf_finish(topo);
err = SYSCTL_OUT(req, sbuf_data(topo), sbuf_len(topo));
}
sbuf_delete(topo);
return (err);
}
#endif
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);
if (error != 0 || req->newptr == NULL)
return (error);
if (new_val <= 0)
return (EINVAL);
sched_slice = imax(1, (new_val + period / 2) / period);
sched_slice_min = sched_slice / SCHED_SLICE_MIN_DIVISOR;
hogticks = imax(1, (2 * hz * sched_slice + realstathz / 2) /
realstathz);
return (0);
}
SYSCTL_NODE(_kern, OID_AUTO, sched, CTLFLAG_RW, 0, "Scheduler");
SYSCTL_STRING(_kern_sched, OID_AUTO, name, CTLFLAG_RD, "ULE", 0,
"Scheduler name");
SYSCTL_PROC(_kern_sched, OID_AUTO, quantum, CTLTYPE_INT | CTLFLAG_RW,
NULL, 0, sysctl_kern_quantum, "I",
"Quantum for timeshare threads in microseconds");
SYSCTL_INT(_kern_sched, OID_AUTO, slice, CTLFLAG_RW, &sched_slice, 0,
"Quantum for timeshare threads in stathz ticks");
SYSCTL_INT(_kern_sched, OID_AUTO, interact, CTLFLAG_RW, &sched_interact, 0,
"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");
#ifdef SMP
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");
SYSCTL_INT(_kern_sched, OID_AUTO, balance_interval, CTLFLAG_RW,
&balance_interval, 0,
"Average period in stathz ticks to run the long-term balancer");
SYSCTL_INT(_kern_sched, OID_AUTO, steal_idle, CTLFLAG_RW, &steal_idle, 0,
"Attempts to steal work from other cores before idling");
SYSCTL_INT(_kern_sched, OID_AUTO, steal_thresh, CTLFLAG_RW, &steal_thresh, 0,
"Minimum load on remote CPU before we'll steal");
SYSCTL_PROC(_kern_sched, OID_AUTO, topology_spec, CTLTYPE_STRING |
CTLFLAG_RD, NULL, 0, sysctl_kern_sched_topology_spec, "A",
"XML dump of detected CPU topology");
#endif
/* ps compat. All cpu percentages from ULE are weighted. */
static int ccpu = 0;
SYSCTL_INT(_kern, OID_AUTO, ccpu, CTLFLAG_RD, &ccpu, 0, "");
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