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freebsd-dev/sys/kern/sched_ule.c
Jeff Roberson 317da70593 - sched_prio() should only adjust tdq_lowpri if the thread is running or on 
a run-queue.  If the priority is numerically raised only change lowpri
   if we're certain it will be correct.  Some slop is allowed however
   previously we could erroneously raise lowpri for an idle cpu that a
   thread had recently run on which lead to errors in load balancing
   decisions.
2008-01-23 03:10:18 +00:00

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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/lock.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/resource.h>
#include <sys/resourcevar.h>
#include <sys/sched.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>
#ifdef KTRACE
#include <sys/uio.h>
#include <sys/ktrace.h>
#endif
#ifdef HWPMC_HOOKS
#include <sys/pmckern.h>
#endif
#include <machine/cpu.h>
#include <machine/smp.h>
#if !defined(__i386__) && !defined(__amd64__) && !defined(__powerpc__) && !defined(__arm__)
#error "This architecture is not currently compatible with ULE"
#endif
#define KTR_ULE 0
/*
* Thread scheduler specific section. All fields are protected
* by the thread lock.
*/
struct td_sched {
TAILQ_ENTRY(td_sched) ts_procq; /* Run queue. */
struct thread *ts_thread; /* Active associated thread. */
struct runq *ts_runq; /* Run-queue we're queued on. */
short ts_flags; /* TSF_* flags. */
u_char ts_rqindex; /* Run queue index. */
u_char ts_cpu; /* CPU that we have affinity for. */
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 */
/* The following variables are only used for pctcpu calculation */
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 SMP
int ts_rltick; /* Real last tick, for affinity. */
#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;
/*
* 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_TIMESHARE + SCHED_PRI_NHALF)
#define SCHED_PRI_MAX (PRI_MAX_TIMESHARE - SCHED_PRI_NHALF)
#define SCHED_PRI_RANGE (SCHED_PRI_MAX - SCHED_PRI_MIN)
#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: Threshhold 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)
/*
* 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 realstathz;
static int tickincr;
static int sched_slice;
#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
/*
* 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 {
struct mtx *tdq_lock; /* Pointer to group lock. */
struct runq tdq_realtime; /* real-time run queue. */
struct runq tdq_timeshare; /* timeshare run queue. */
struct runq tdq_idle; /* Queue of IDLE threads. */
int tdq_load; /* Aggregate load. */
u_char tdq_idx; /* Current insert index. */
u_char tdq_ridx; /* Current removal index. */
#ifdef SMP
u_char tdq_lowpri; /* Lowest priority thread. */
int tdq_transferable; /* Transferable thread count. */
LIST_ENTRY(tdq) tdq_siblings; /* Next in tdq group. */
struct tdq_group *tdq_group; /* Our processor group. */
#else
int tdq_sysload; /* For loadavg, !ITHD load. */
#endif
} __aligned(64);
#ifdef SMP
/*
* tdq groups are groups of processors which can cheaply share threads. When
* one processor in the group goes idle it will check the runqs of the other
* processors in its group prior to halting and waiting for an interrupt.
* These groups are suitable for SMT (Symetric Multi-Threading) and not NUMA.
* In a numa environment we'd want an idle bitmap per group and a two tiered
* load balancer.
*/
struct tdq_group {
struct mtx tdg_lock; /* Protects all fields below. */
int tdg_cpus; /* Count of CPUs in this tdq group. */
cpumask_t tdg_cpumask; /* Mask of cpus in this group. */
cpumask_t tdg_idlemask; /* Idle cpus in this group. */
cpumask_t tdg_mask; /* Bit mask for first cpu. */
int tdg_load; /* Total load of this group. */
int tdg_transferable; /* Transferable load of this group. */
LIST_HEAD(, tdq) tdg_members; /* Linked list of all members. */
char tdg_name[16]; /* lock name. */
} __aligned(64);
#define SCHED_AFFINITY_DEFAULT (max(1, hz / 300))
#define SCHED_AFFINITY(ts) ((ts)->ts_rltick > ticks - affinity)
/*
* Run-time tunables.
*/
static int rebalance = 1;
static int balance_interval = 128; /* Default set in sched_initticks(). */
static int pick_pri = 1;
static int affinity;
static int tryself = 1;
static int steal_htt = 1;
static int steal_idle = 1;
static int steal_thresh = 2;
static int topology = 0;
/*
* One thread queue per processor.
*/
static volatile cpumask_t tdq_idle;
static int tdg_maxid;
static struct tdq tdq_cpu[MAXCPU];
static struct tdq_group tdq_groups[MAXCPU];
static struct tdq *balance_tdq;
static int balance_group_ticks;
static int balance_ticks;
#define TDQ_SELF() (&tdq_cpu[PCPU_GET(cpuid)])
#define TDQ_CPU(x) (&tdq_cpu[(x)])
#define TDQ_ID(x) ((int)((x) - tdq_cpu))
#define TDQ_GROUP(x) (&tdq_groups[(x)])
#define TDG_ID(x) ((int)((x) - tdq_groups))
#else /* !SMP */
static struct tdq tdq_cpu;
static struct mtx tdq_lock;
#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) ((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 *);
/* Operations on per processor queues */
static struct td_sched * tdq_choose(struct tdq *);
static void tdq_setup(struct tdq *);
static void tdq_load_add(struct tdq *, struct td_sched *);
static void tdq_load_rem(struct tdq *, struct td_sched *);
static __inline void tdq_runq_add(struct tdq *, struct td_sched *, int);
static __inline void tdq_runq_rem(struct tdq *, struct td_sched *);
void tdq_print(int cpu);
static void runq_print(struct runq *rq);
static void tdq_add(struct tdq *, struct thread *, int);
#ifdef SMP
static void tdq_move(struct tdq *, struct tdq *);
static int tdq_idled(struct tdq *);
static void tdq_notify(struct td_sched *);
static struct td_sched *tdq_steal(struct tdq *);
static struct td_sched *runq_steal(struct runq *);
static int sched_pickcpu(struct td_sched *, int);
static void sched_balance(void);
static void sched_balance_groups(void);
static void sched_balance_group(struct tdq_group *);
static void sched_balance_pair(struct tdq *, struct tdq *);
static inline struct tdq *sched_setcpu(struct td_sched *, int, int);
static inline struct mtx *thread_block_switch(struct thread *);
static inline void thread_unblock_switch(struct thread *, struct mtx *);
static struct mtx *sched_switch_migrate(struct tdq *, struct thread *, int);
#define THREAD_CAN_MIGRATE(td) ((td)->td_pinned == 0)
#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)
/*
* Print the threads waiting on a run-queue.
*/
static void
runq_print(struct runq *rq)
{
struct rqhead *rqh;
struct td_sched *ts;
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(ts, rqh, ts_procq) {
printf("\t\t\ttd %p(%s) priority %d rqindex %d pri %d\n",
ts->ts_thread, ts->ts_thread->td_name, ts->ts_thread->td_priority, ts->ts_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("\tlockptr %p\n", TDQ_LOCKPTR(tdq));
printf("\tload: %d\n", tdq->tdq_load);
printf("\ttimeshare idx: %d\n", tdq->tdq_idx);
printf("\ttimeshare ridx: %d\n", tdq->tdq_ridx);
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);
#ifdef SMP
printf("\tload transferable: %d\n", tdq->tdq_transferable);
printf("\tlowest priority: %d\n", tdq->tdq_lowpri);
printf("\tgroup: %d\n", TDG_ID(tdq->tdq_group));
printf("\tLock name: %s\n", tdq->tdq_group->tdg_name);
#endif
}
#define TS_RQ_PPQ (((PRI_MAX_TIMESHARE - PRI_MIN_TIMESHARE) + 1) / RQ_NQS)
/*
* 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 td_sched *ts, int flags)
{
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
THREAD_LOCK_ASSERT(ts->ts_thread, MA_OWNED);
#ifdef SMP
if (THREAD_CAN_MIGRATE(ts->ts_thread)) {
tdq->tdq_transferable++;
tdq->tdq_group->tdg_transferable++;
ts->ts_flags |= TSF_XFERABLE;
}
#endif
if (ts->ts_runq == &tdq->tdq_timeshare) {
u_char pri;
pri = ts->ts_thread->td_priority;
KASSERT(pri <= PRI_MAX_TIMESHARE && pri >= PRI_MIN_TIMESHARE,
("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 = (pri - PRI_MIN_TIMESHARE) / TS_RQ_PPQ;
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, ts, pri, flags);
} else
runq_add(ts->ts_runq, ts, 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 td_sched *ts)
{
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
KASSERT(ts->ts_runq != NULL,
("tdq_runq_remove: thread %p null ts_runq", ts->ts_thread));
#ifdef SMP
if (ts->ts_flags & TSF_XFERABLE) {
tdq->tdq_transferable--;
tdq->tdq_group->tdg_transferable--;
ts->ts_flags &= ~TSF_XFERABLE;
}
#endif
if (ts->ts_runq == &tdq->tdq_timeshare) {
if (tdq->tdq_idx != tdq->tdq_ridx)
runq_remove_idx(ts->ts_runq, ts, &tdq->tdq_ridx);
else
runq_remove_idx(ts->ts_runq, ts, NULL);
/*
* For timeshare threads we update the priority here so
* the priority reflects the time we've been sleeping.
*/
ts->ts_ltick = ticks;
sched_pctcpu_update(ts);
sched_priority(ts->ts_thread);
} else
runq_remove(ts->ts_runq, ts);
}
/*
* 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 td_sched *ts)
{
int class;
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
THREAD_LOCK_ASSERT(ts->ts_thread, MA_OWNED);
class = PRI_BASE(ts->ts_thread->td_pri_class);
tdq->tdq_load++;
CTR2(KTR_SCHED, "cpu %d load: %d", TDQ_ID(tdq), tdq->tdq_load);
if (class != PRI_ITHD &&
(ts->ts_thread->td_proc->p_flag & P_NOLOAD) == 0)
#ifdef SMP
tdq->tdq_group->tdg_load++;
#else
tdq->tdq_sysload++;
#endif
}
/*
* Remove the load from a thread that is transitioning to a sleep state or
* exiting.
*/
static void
tdq_load_rem(struct tdq *tdq, struct td_sched *ts)
{
int class;
THREAD_LOCK_ASSERT(ts->ts_thread, MA_OWNED);
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
class = PRI_BASE(ts->ts_thread->td_pri_class);
if (class != PRI_ITHD &&
(ts->ts_thread->td_proc->p_flag & P_NOLOAD) == 0)
#ifdef SMP
tdq->tdq_group->tdg_load--;
#else
tdq->tdq_sysload--;
#endif
KASSERT(tdq->tdq_load != 0,
("tdq_load_rem: Removing with 0 load on queue %d", TDQ_ID(tdq)));
tdq->tdq_load--;
CTR1(KTR_SCHED, "load: %d", tdq->tdq_load);
ts->ts_runq = NULL;
}
#ifdef SMP
/*
* sched_balance is a simple CPU load balancing algorithm. It operates by
* finding the least loaded and most loaded cpu and equalizing their load
* by migrating some processes.
*
* Dealing only with two CPUs at a time has two advantages. Firstly, most
* installations will only have 2 cpus. Secondly, load balancing too much at
* once can have an unpleasant effect on the system. The scheduler rarely has
* enough information to make perfect decisions. So this algorithm chooses
* simplicity and more gradual effects on load in larger systems.
*
*/
static void
sched_balance()
{
struct tdq_group *high;
struct tdq_group *low;
struct tdq_group *tdg;
struct tdq *tdq;
int cnt;
int i;
/*
* 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);
low = high = NULL;
i = random() % (tdg_maxid + 1);
for (cnt = 0; cnt <= tdg_maxid; cnt++) {
tdg = TDQ_GROUP(i);
/*
* Find the CPU with the highest load that has some
* threads to transfer.
*/
if ((high == NULL || tdg->tdg_load > high->tdg_load)
&& tdg->tdg_transferable)
high = tdg;
if (low == NULL || tdg->tdg_load < low->tdg_load)
low = tdg;
if (++i > tdg_maxid)
i = 0;
}
if (low != NULL && high != NULL && high != low)
sched_balance_pair(LIST_FIRST(&high->tdg_members),
LIST_FIRST(&low->tdg_members));
TDQ_LOCK(tdq);
}
/*
* Balance load between CPUs in a group. Will only migrate within the group.
*/
static void
sched_balance_groups()
{
struct tdq *tdq;
int i;
/*
* Select a random time between .5 * balance_interval and
* 1.5 * balance_interval.
*/
balance_group_ticks = max(balance_interval / 2, 1);
balance_group_ticks += random() % balance_interval;
if (smp_started == 0 || rebalance == 0)
return;
tdq = TDQ_SELF();
TDQ_UNLOCK(tdq);
for (i = 0; i <= tdg_maxid; i++)
sched_balance_group(TDQ_GROUP(i));
TDQ_LOCK(tdq);
}
/*
* Finds the greatest imbalance between two tdqs in a group.
*/
static void
sched_balance_group(struct tdq_group *tdg)
{
struct tdq *tdq;
struct tdq *high;
struct tdq *low;
int load;
if (tdg->tdg_transferable == 0)
return;
low = NULL;
high = NULL;
LIST_FOREACH(tdq, &tdg->tdg_members, tdq_siblings) {
load = tdq->tdq_load;
if (high == NULL || load > high->tdq_load)
high = tdq;
if (low == NULL || load < low->tdq_load)
low = tdq;
}
if (high != NULL && low != NULL && high != low)
sched_balance_pair(high, low);
}
/*
* 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 void
sched_balance_pair(struct tdq *high, struct tdq *low)
{
int transferable;
int high_load;
int low_load;
int move;
int diff;
int i;
tdq_lock_pair(high, low);
/*
* If we're transfering within a group we have to use this specific
* tdq's transferable count, otherwise we can steal from other members
* of the group.
*/
if (high->tdq_group == low->tdq_group) {
transferable = high->tdq_transferable;
high_load = high->tdq_load;
low_load = low->tdq_load;
} else {
transferable = high->tdq_group->tdg_transferable;
high_load = high->tdq_group->tdg_load;
low_load = low->tdq_group->tdg_load;
}
/*
* Determine what the imbalance is and then adjust that to how many
* threads we actually have to give up (transferable).
*/
if (transferable != 0) {
diff = high_load - low_load;
move = diff / 2;
if (diff & 0x1)
move++;
move = min(move, transferable);
for (i = 0; i < move; i++)
tdq_move(high, low);
/*
* IPI the target cpu to force it to reschedule with the new
* workload.
*/
ipi_selected(1 << TDQ_ID(low), IPI_PREEMPT);
}
tdq_unlock_pair(high, low);
return;
}
/*
* Move a thread from one thread queue to another.
*/
static void
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);
ts = tdq_steal(tdq);
if (ts == NULL) {
struct tdq_group *tdg;
tdg = tdq->tdq_group;
LIST_FOREACH(tdq, &tdg->tdg_members, tdq_siblings) {
if (tdq == from || tdq->tdq_transferable == 0)
continue;
ts = tdq_steal(tdq);
break;
}
if (ts == NULL)
return;
}
if (tdq == to)
return;
td = ts->ts_thread;
/*
* 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);
}
/*
* This tdq has idled. Try to steal a thread from another cpu and switch
* to it.
*/
static int
tdq_idled(struct tdq *tdq)
{
struct tdq_group *tdg;
struct tdq *steal;
int highload;
int highcpu;
int cpu;
if (smp_started == 0 || steal_idle == 0)
return (1);
/* We don't want to be preempted while we're iterating over tdqs */
spinlock_enter();
tdg = tdq->tdq_group;
/*
* If we're in a cpu group, try and steal threads from another cpu in
* the group before idling. In a HTT group all cpus share the same
* run-queue lock, however, we still need a recursive lock to
* call tdq_move().
*/
if (steal_htt && tdg->tdg_cpus > 1 && tdg->tdg_transferable) {
TDQ_LOCK(tdq);
LIST_FOREACH(steal, &tdg->tdg_members, tdq_siblings) {
if (steal == tdq || steal->tdq_transferable == 0)
continue;
TDQ_LOCK(steal);
goto steal;
}
TDQ_UNLOCK(tdq);
}
/*
* Find the least loaded CPU with a transferable thread and attempt
* to steal it. We make a lockless pass and then verify that the
* thread is still available after locking.
*/
for (;;) {
highcpu = 0;
highload = 0;
for (cpu = 0; cpu <= mp_maxid; cpu++) {
if (CPU_ABSENT(cpu))
continue;
steal = TDQ_CPU(cpu);
if (steal->tdq_transferable == 0)
continue;
if (steal->tdq_load < highload)
continue;
highload = steal->tdq_load;
highcpu = cpu;
}
if (highload < steal_thresh)
break;
steal = TDQ_CPU(highcpu);
if (steal == tdq)
break;
tdq_lock_pair(tdq, steal);
if (steal->tdq_load >= steal_thresh && steal->tdq_transferable)
goto steal;
tdq_unlock_pair(tdq, steal);
}
spinlock_exit();
return (1);
steal:
spinlock_exit();
tdq_move(steal, tdq);
TDQ_UNLOCK(steal);
mi_switch(SW_VOL, NULL);
thread_unlock(curthread);
return (0);
}
/*
* Notify a remote cpu of new work. Sends an IPI if criteria are met.
*/
static void
tdq_notify(struct td_sched *ts)
{
struct thread *ctd;
struct pcpu *pcpu;
int cpri;
int pri;
int cpu;
cpu = ts->ts_cpu;
pri = ts->ts_thread->td_priority;
pcpu = pcpu_find(cpu);
ctd = pcpu->pc_curthread;
cpri = ctd->td_priority;
/*
* If our priority is not better than the current priority there is
* nothing to do.
*/
if (pri > cpri)
return;
/*
* Always IPI idle.
*/
if (cpri > PRI_MIN_IDLE)
goto sendipi;
/*
* If we're realtime or better and there is timeshare or worse running
* send an IPI.
*/
if (pri < PRI_MAX_REALTIME && cpri > PRI_MAX_REALTIME)
goto sendipi;
/*
* Otherwise only IPI if we exceed the threshold.
*/
if (pri > preempt_thresh)
return;
sendipi:
ctd->td_flags |= TDF_NEEDRESCHED;
ipi_selected(1 << cpu, IPI_PREEMPT);
}
/*
* Steals load from a timeshare queue. Honors the rotating queue head
* index.
*/
static struct td_sched *
runq_steal_from(struct runq *rq, u_char start)
{
struct td_sched *ts;
struct rqbits *rqb;
struct rqhead *rqh;
int first;
int bit;
int pri;
int i;
rqb = &rq->rq_status;
bit = start & (RQB_BPW -1);
pri = 0;
first = 0;
again:
for (i = RQB_WORD(start); i < RQB_LEN; bit = 0, i++) {
if (rqb->rqb_bits[i] == 0)
continue;
if (bit != 0) {
for (pri = bit; pri < RQB_BPW; pri++)
if (rqb->rqb_bits[i] & (1ul << pri))
break;
if (pri >= RQB_BPW)
continue;
} else
pri = RQB_FFS(rqb->rqb_bits[i]);
pri += (i << RQB_L2BPW);
rqh = &rq->rq_queues[pri];
TAILQ_FOREACH(ts, rqh, ts_procq) {
if (first && THREAD_CAN_MIGRATE(ts->ts_thread))
return (ts);
first = 1;
}
}
if (start != 0) {
start = 0;
goto again;
}
return (NULL);
}
/*
* Steals load from a standard linear queue.
*/
static struct td_sched *
runq_steal(struct runq *rq)
{
struct rqhead *rqh;
struct rqbits *rqb;
struct td_sched *ts;
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(ts, rqh, ts_procq)
if (THREAD_CAN_MIGRATE(ts->ts_thread))
return (ts);
}
}
return (NULL);
}
/*
* Attempt to steal a thread in priority order from a thread queue.
*/
static struct td_sched *
tdq_steal(struct tdq *tdq)
{
struct td_sched *ts;
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
if ((ts = runq_steal(&tdq->tdq_realtime)) != NULL)
return (ts);
if ((ts = runq_steal_from(&tdq->tdq_timeshare, tdq->tdq_ridx)) != NULL)
return (ts);
return (runq_steal(&tdq->tdq_idle));
}
/*
* 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 td_sched *ts, int cpu, int flags)
{
struct thread *td;
struct tdq *tdq;
THREAD_LOCK_ASSERT(ts->ts_thread, MA_OWNED);
tdq = TDQ_CPU(cpu);
td = ts->ts_thread;
ts->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.
*/
thread_lock_block(td);
TDQ_LOCK(tdq);
thread_lock_unblock(td, TDQ_LOCKPTR(tdq));
return (tdq);
}
/*
* Find the thread queue running the lowest priority thread.
*/
static int
tdq_lowestpri(void)
{
struct tdq *tdq;
int lowpri;
int lowcpu;
int lowload;
int load;
int cpu;
int pri;
lowload = 0;
lowpri = lowcpu = 0;
for (cpu = 0; cpu <= mp_maxid; cpu++) {
if (CPU_ABSENT(cpu))
continue;
tdq = TDQ_CPU(cpu);
pri = tdq->tdq_lowpri;
load = TDQ_CPU(cpu)->tdq_load;
CTR4(KTR_ULE,
"cpu %d pri %d lowcpu %d lowpri %d",
cpu, pri, lowcpu, lowpri);
if (pri < lowpri)
continue;
if (lowpri && lowpri == pri && load > lowload)
continue;
lowpri = pri;
lowcpu = cpu;
lowload = load;
}
return (lowcpu);
}
/*
* Find the thread queue with the least load.
*/
static int
tdq_lowestload(void)
{
struct tdq *tdq;
int lowload;
int lowpri;
int lowcpu;
int load;
int cpu;
int pri;
lowcpu = 0;
lowload = TDQ_CPU(0)->tdq_load;
lowpri = TDQ_CPU(0)->tdq_lowpri;
for (cpu = 1; cpu <= mp_maxid; cpu++) {
if (CPU_ABSENT(cpu))
continue;
tdq = TDQ_CPU(cpu);
load = tdq->tdq_load;
pri = tdq->tdq_lowpri;
CTR4(KTR_ULE, "cpu %d load %d lowcpu %d lowload %d",
cpu, load, lowcpu, lowload);
if (load > lowload)
continue;
if (load == lowload && pri < lowpri)
continue;
lowcpu = cpu;
lowload = load;
lowpri = pri;
}
return (lowcpu);
}
/*
* Pick the destination cpu for sched_add(). Respects affinity and makes
* a determination based on load or priority of available processors.
*/
static int
sched_pickcpu(struct td_sched *ts, int flags)
{
struct tdq *tdq;
int self;
int pri;
int cpu;
cpu = self = PCPU_GET(cpuid);
if (smp_started == 0)
return (self);
/*
* Don't migrate a running thread from sched_switch().
*/
if (flags & SRQ_OURSELF) {
CTR1(KTR_ULE, "YIELDING %d",
curthread->td_priority);
return (self);
}
pri = ts->ts_thread->td_priority;
cpu = ts->ts_cpu;
/*
* Regardless of affinity, if the last cpu is idle send it there.
*/
tdq = TDQ_CPU(cpu);
if (tdq->tdq_lowpri > PRI_MIN_IDLE) {
CTR5(KTR_ULE,
"ts_cpu %d idle, ltick %d ticks %d pri %d curthread %d",
ts->ts_cpu, ts->ts_rltick, ticks, pri,
tdq->tdq_lowpri);
return (ts->ts_cpu);
}
/*
* If we have affinity, try to place it on the cpu we last ran on.
*/
if (SCHED_AFFINITY(ts) && tdq->tdq_lowpri > pri) {
CTR5(KTR_ULE,
"affinity for %d, ltick %d ticks %d pri %d curthread %d",
ts->ts_cpu, ts->ts_rltick, ticks, pri,
tdq->tdq_lowpri);
return (ts->ts_cpu);
}
/*
* Look for an idle group.
*/
CTR1(KTR_ULE, "tdq_idle %X", tdq_idle);
cpu = ffs(tdq_idle);
if (cpu)
return (--cpu);
/*
* If there are no idle cores see if we can run the thread locally.
* This may improve locality among sleepers and wakers when there
* is shared data.
*/
if (tryself && pri < TDQ_CPU(self)->tdq_lowpri) {
CTR1(KTR_ULE, "tryself %d",
curthread->td_priority);
return (self);
}
/*
* Now search for the cpu running the lowest priority thread with
* the least load.
*/
if (pick_pri)
cpu = tdq_lowestpri();
else
cpu = tdq_lowestload();
return (cpu);
}
#endif /* SMP */
/*
* Pick the highest priority task we have and return it.
*/
static struct td_sched *
tdq_choose(struct tdq *tdq)
{
struct td_sched *ts;
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
ts = runq_choose(&tdq->tdq_realtime);
if (ts != NULL)
return (ts);
ts = runq_choose_from(&tdq->tdq_timeshare, tdq->tdq_ridx);
if (ts != NULL) {
KASSERT(ts->ts_thread->td_priority >= PRI_MIN_TIMESHARE,
("tdq_choose: Invalid priority on timeshare queue %d",
ts->ts_thread->td_priority));
return (ts);
}
ts = runq_choose(&tdq->tdq_idle);
if (ts != NULL) {
KASSERT(ts->ts_thread->td_priority >= PRI_MIN_IDLE,
("tdq_choose: Invalid priority on idle queue %d",
ts->ts_thread->td_priority));
return (ts);
}
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);
tdq->tdq_load = 0;
}
#ifdef SMP
static void
tdg_setup(struct tdq_group *tdg)
{
if (bootverbose)
printf("ULE: setup cpu group %d\n", TDG_ID(tdg));
snprintf(tdg->tdg_name, sizeof(tdg->tdg_name),
"sched lock %d", (int)TDG_ID(tdg));
mtx_init(&tdg->tdg_lock, tdg->tdg_name, "sched lock",
MTX_SPIN | MTX_RECURSE);
LIST_INIT(&tdg->tdg_members);
tdg->tdg_load = 0;
tdg->tdg_transferable = 0;
tdg->tdg_cpus = 0;
tdg->tdg_mask = 0;
tdg->tdg_cpumask = 0;
tdg->tdg_idlemask = 0;
}
static void
tdg_add(struct tdq_group *tdg, struct tdq *tdq)
{
if (tdg->tdg_mask == 0)
tdg->tdg_mask |= 1 << TDQ_ID(tdq);
tdg->tdg_cpumask |= 1 << TDQ_ID(tdq);
tdg->tdg_cpus++;
tdq->tdq_group = tdg;
tdq->tdq_lock = &tdg->tdg_lock;
LIST_INSERT_HEAD(&tdg->tdg_members, tdq, tdq_siblings);
if (bootverbose)
printf("ULE: adding cpu %d to group %d: cpus %d mask 0x%X\n",
TDQ_ID(tdq), TDG_ID(tdg), tdg->tdg_cpus, tdg->tdg_cpumask);
}
static void
sched_setup_topology(void)
{
struct tdq_group *tdg;
struct cpu_group *cg;
int balance_groups;
struct tdq *tdq;
int i;
int j;
topology = 1;
balance_groups = 0;
for (i = 0; i < smp_topology->ct_count; i++) {
cg = &smp_topology->ct_group[i];
tdg = &tdq_groups[i];
/*
* Initialize the group.
*/
tdg_setup(tdg);
/*
* Find all of the group members and add them.
*/
for (j = 0; j < MAXCPU; j++) {
if ((cg->cg_mask & (1 << j)) != 0) {
tdq = TDQ_CPU(j);
tdq_setup(tdq);
tdg_add(tdg, tdq);
}
}
if (tdg->tdg_cpus > 1)
balance_groups = 1;
}
tdg_maxid = smp_topology->ct_count - 1;
if (balance_groups)
sched_balance_groups();
}
static void
sched_setup_smp(void)
{
struct tdq_group *tdg;
struct tdq *tdq;
int cpus;
int i;
for (cpus = 0, i = 0; i < MAXCPU; i++) {
if (CPU_ABSENT(i))
continue;
tdq = &tdq_cpu[i];
tdg = &tdq_groups[i];
/*
* Setup a tdq group with one member.
*/
tdg_setup(tdg);
tdq_setup(tdq);
tdg_add(tdg, tdq);
cpus++;
}
tdg_maxid = cpus - 1;
}
/*
* Fake a topology with one group containing all CPUs.
*/
static void
sched_fake_topo(void)
{
#ifdef SCHED_FAKE_TOPOLOGY
static struct cpu_top top;
static struct cpu_group group;
top.ct_count = 1;
top.ct_group = &group;
group.cg_mask = all_cpus;
group.cg_count = mp_ncpus;
group.cg_children = 0;
smp_topology = &top;
#endif
}
#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_fake_topo();
/*
* Setup tdqs based on a topology configuration or vanilla SMP based
* on mp_maxid.
*/
if (smp_topology == NULL)
sched_setup_smp();
else
sched_setup_topology();
balance_tdq = tdq;
sched_balance();
#else
tdq_setup(tdq);
mtx_init(&tdq_lock, "sched lock", "sched lock", MTX_SPIN | MTX_RECURSE);
tdq->tdq_lock = &tdq_lock;
#endif
/*
* To avoid divide-by-zero, we set realstathz a dummy value
* in case which sched_clock() called before sched_initticks().
*/
realstathz = hz;
sched_slice = (realstathz/10); /* ~100ms */
tickincr = 1 << SCHED_TICK_SHIFT;
/* Add thread0's load since it's running. */
TDQ_LOCK(tdq);
thread0.td_lock = TDQ_LOCKPTR(TDQ_SELF());
tdq_load_add(tdq, &td_sched0);
TDQ_UNLOCK(tdq);
}
/*
* This routine determines the tickincr after stathz and hz are setup.
*/
/* ARGSUSED */
static void
sched_initticks(void *dummy)
{
int incr;
realstathz = stathz ? stathz : hz;
sched_slice = (realstathz/10); /* ~100ms */
/*
* 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;
/*
* Set steal thresh to log2(mp_ncpu) but no greater than 4. This
* prevents excess thrashing on large machines and excess idle on
* smaller machines.
*/
steal_thresh = min(ffs(mp_ncpus) - 1, 4);
affinity = SCHED_AFFINITY_DEFAULT;
#endif
}
/*
* 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 (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_REALTIME;
pri += ((PRI_MAX_REALTIME - PRI_MIN_REALTIME) / sched_interact)
* score;
KASSERT(pri >= PRI_MIN_REALTIME && pri <= PRI_MAX_REALTIME,
("sched_priority: invalid interactive priority %d score %d",
pri, score));
} else {
pri = SCHED_PRI_MIN;
if (td->td_sched->ts_ticks)
pri += SCHED_PRI_TICKS(td->td_sched);
pri += SCHED_PRI_NICE(td->td_proc->p_nice);
KASSERT(pri >= PRI_MIN_TIMESHARE && pri <= PRI_MAX_TIMESHARE,
("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_thread = &thread0;
}
/*
* 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 to hz */
return (hz/(realstathz/sched_slice));
}
/*
* 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)
{
if (ts->ts_ticks == 0)
return;
if (ticks - (hz / 10) < ts->ts_ltick &&
SCHED_TICK_TOTAL(ts) < SCHED_TICK_MAX)
return;
/*
* Adjust counters and watermark for pctcpu calc.
*/
if (ts->ts_ltick > ticks - SCHED_TICK_TARG)
ts->ts_ticks = (ts->ts_ticks / (ticks - ts->ts_ftick)) *
SCHED_TICK_TARG;
else
ts->ts_ticks = 0;
ts->ts_ltick = ticks;
ts->ts_ftick = ts->ts_ltick - SCHED_TICK_TARG;
}
/*
* 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;
CTR6(KTR_SCHED, "sched_prio: %p(%s) prio %d newprio %d by %p(%s)",
td, td->td_name, td->td_priority, prio, curthread,
curthread->td_name);
ts = td->td_sched;
THREAD_LOCK_ASSERT(td, MA_OWNED);
if (td->td_priority == prio)
return;
if (TD_ON_RUNQ(td) && prio < td->td_priority) {
/*
* 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.
*/
sched_rem(td);
td->td_priority = prio;
sched_add(td, SRQ_BORROWING);
#ifdef SMP
} else if (TD_IS_RUNNING(td)) {
struct tdq *tdq;
tdq = TDQ_CPU(ts->ts_cpu);
if (prio < tdq->tdq_lowpri ||
(td->td_priority == tdq->tdq_lowpri && tdq->tdq_load <= 1))
tdq->tdq_lowpri = prio;
td->td_priority = prio;
#endif
} else
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)
{
u_char oldprio;
td->td_base_user_pri = prio;
if (td->td_flags & TDF_UBORROWING && td->td_user_pri <= prio)
return;
oldprio = td->td_user_pri;
td->td_user_pri = prio;
}
void
sched_lend_user_prio(struct thread *td, u_char prio)
{
u_char oldprio;
THREAD_LOCK_ASSERT(td, MA_OWNED);
td->td_flags |= TDF_UBORROWING;
oldprio = td->td_user_pri;
td->td_user_pri = prio;
}
void
sched_unlend_user_prio(struct thread *td, u_char prio)
{
u_char base_pri;
THREAD_LOCK_ASSERT(td, MA_OWNED);
base_pri = td->td_base_user_pri;
if (prio >= base_pri) {
td->td_flags &= ~TDF_UBORROWING;
sched_user_prio(td, base_pri);
} else {
sched_lend_user_prio(td, prio);
}
}
/*
* Add the thread passed as 'newtd' to the run queue before selecting
* the next thread to run. This is only used for KSE.
*/
static void
sched_switchin(struct tdq *tdq, struct thread *td)
{
#ifdef SMP
spinlock_enter();
TDQ_UNLOCK(tdq);
thread_lock(td);
spinlock_exit();
sched_setcpu(td->td_sched, TDQ_ID(tdq), SRQ_YIELDING);
#else
td->td_lock = TDQ_LOCKPTR(tdq);
#endif
tdq_add(tdq, td, SRQ_YIELDING);
MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
}
/*
* Block a thread for switching. Similar to thread_block() but does not
* bump the spin count.
*/
static inline struct mtx *
thread_block_switch(struct thread *td)
{
struct mtx *lock;
THREAD_LOCK_ASSERT(td, MA_OWNED);
lock = td->td_lock;
td->td_lock = &blocked_lock;
mtx_unlock_spin(lock);
return (lock);
}
/*
* 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
/*
* 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_block_switch(td); /* This releases the lock on tdq. */
TDQ_LOCK(tdn);
tdq_add(tdn, td, flags);
tdq_notify(td->td_sched);
/*
* After we unlock tdn the new cpu still can't switch into this
* thread until we've unblocked it in cpu_switch(). The lock
* pointers may match in the case of HTT cores. Don't unlock here
* or we can deadlock when the other CPU runs the IPI handler.
*/
if (TDQ_LOCKPTR(tdn) != TDQ_LOCKPTR(tdq)) {
TDQ_UNLOCK(tdn);
TDQ_LOCK(tdq);
}
spinlock_exit();
#endif
return (TDQ_LOCKPTR(tdn));
}
/*
* Release a thread that was blocked with thread_block_switch().
*/
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;
THREAD_LOCK_ASSERT(td, MA_OWNED);
cpuid = PCPU_GET(cpuid);
tdq = TDQ_CPU(cpuid);
ts = td->td_sched;
mtx = td->td_lock;
#ifdef SMP
ts->ts_rltick = ticks;
#endif
td->td_lastcpu = td->td_oncpu;
td->td_oncpu = NOCPU;
td->td_flags &= ~TDF_NEEDRESCHED;
td->td_owepreempt = 0;
/*
* 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));
tdq_load_rem(tdq, ts);
srqflag = (flags & SW_PREEMPT) ?
SRQ_OURSELF|SRQ_YIELDING|SRQ_PREEMPTED :
SRQ_OURSELF|SRQ_YIELDING;
if (ts->ts_cpu == cpuid)
tdq_add(tdq, td, srqflag);
else
mtx = sched_switch_migrate(tdq, td, srqflag);
} else {
/* This thread must be going to sleep. */
TDQ_LOCK(tdq);
mtx = thread_block_switch(td);
tdq_load_rem(tdq, ts);
}
/*
* 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);
/*
* If KSE assigned a new thread just add it here and let choosethread
* select the best one.
*/
if (newtd != NULL)
sched_switchin(tdq, newtd);
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
lock_profile_release_lock(&TDQ_LOCKPTR(tdq)->lock_object);
TDQ_LOCKPTR(tdq)->mtx_lock = (uintptr_t)newtd;
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__);
#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);
/*
* Assert that all went well and return.
*/
#ifdef SMP
/* We should always get here with the lowest priority td possible */
tdq->tdq_lowpri = td->td_priority;
#endif
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);
PROC_SLOCK_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)
{
THREAD_LOCK_ASSERT(td, MA_OWNED);
td->td_slptick = ticks;
}
/*
* 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;
/*
* 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) {
u_int hzticks;
hzticks = (ticks - slptick) << SCHED_TICK_SHIFT;
ts->ts_slptime += hzticks;
sched_interact_update(td);
sched_pctcpu_update(ts);
sched_priority(td);
}
/* Reset the slice value after we sleep. */
ts->ts_slice = sched_slice;
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_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;
/*
* Initialize child.
*/
THREAD_LOCK_ASSERT(td, MA_OWNED);
sched_newthread(child);
child->td_lock = TDQ_LOCKPTR(TDQ_SELF());
ts = td->td_sched;
ts2 = child->td_sched;
ts2->ts_cpu = ts->ts_cpu;
ts2->ts_runq = NULL;
/*
* Grab our parents cpu estimation information and priority.
*/
ts2->ts_ticks = ts->ts_ticks;
ts2->ts_ltick = ts->ts_ltick;
ts2->ts_ftick = ts->ts_ftick;
child->td_user_pri = td->td_user_pri;
child->td_base_user_pri = td->td_base_user_pri;
/*
* And update interactivity score.
*/
ts2->ts_slptime = ts->ts_slptime;
ts2->ts_runtime = ts->ts_runtime;
ts2->ts_slice = 1; /* Attempt to quickly learn interactivity. */
}
/*
* 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;
#ifdef SMP
/*
* On SMP if we're on the RUNQ we must adjust the transferable
* count because could be changing to or from an interrupt
* class.
*/
if (TD_ON_RUNQ(td)) {
struct tdq *tdq;
tdq = TDQ_CPU(td->td_sched->ts_cpu);
if (THREAD_CAN_MIGRATE(td)) {
tdq->tdq_transferable--;
tdq->tdq_group->tdg_transferable--;
}
td->td_pri_class = class;
if (THREAD_CAN_MIGRATE(td)) {
tdq->tdq_transferable++;
tdq->tdq_group->tdg_transferable++;
}
}
#endif
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;
CTR3(KTR_SCHED, "sched_exit: %p(%s) prio %d",
child, child->td_name, child->td_priority);
PROC_SLOCK_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)
{
CTR3(KTR_SCHED, "sched_exit_thread: %p(%s) prio %d",
child, child->td_name, child->td_priority);
#ifdef KSE
/*
* KSE forks and exits so often that this penalty causes short-lived
* threads to always be non-interactive. This causes mozilla to
* crawl under load.
*/
if ((td->td_pflags & TDP_SA) && td->td_proc == child->td_proc)
return;
#endif
/*
* 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);
}
/*
* 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;
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();
if (balance_group_ticks && --balance_group_ticks == 0)
sched_balance_groups();
}
#endif
/*
* 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;
if (td->td_pri_class & PRI_FIFO_BIT)
return;
if (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);
}
/*
* We used up one time slice.
*/
if (--ts->ts_slice > 0)
return;
/*
* We're out of time, recompute priorities and requeue.
*/
sched_priority(td);
td->td_flags |= TDF_NEEDRESCHED;
}
/*
* Called once per hz tick. Used for cpu utilization information. This
* is easier than trying to scale based on stathz.
*/
void
sched_tick(void)
{
struct td_sched *ts;
ts = curthread->td_sched;
/* Adjust ticks for pctcpu */
ts->ts_ticks += 1 << SCHED_TICK_SHIFT;
ts->ts_ltick = ticks;
/*
* Update if we've exceeded our desired tick threshhold by over one
* second.
*/
if (ts->ts_ftick + SCHED_TICK_MAX < ts->ts_ltick)
sched_pctcpu_update(ts);
}
/*
* 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)
{
#ifdef SMP
struct tdq_group *tdg;
#endif
struct td_sched *ts;
struct thread *td;
struct tdq *tdq;
tdq = TDQ_SELF();
TDQ_LOCK_ASSERT(tdq, MA_OWNED);
ts = tdq_choose(tdq);
if (ts) {
tdq_runq_rem(tdq, ts);
return (ts->ts_thread);
}
td = PCPU_GET(idlethread);
#ifdef SMP
/*
* We only set the idled bit when all of the cpus in the group are
* idle. Otherwise we could get into a situation where a thread bounces
* back and forth between two idle cores on seperate physical CPUs.
*/
tdg = tdq->tdq_group;
tdg->tdg_idlemask |= PCPU_GET(cpumask);
if (tdg->tdg_idlemask == tdg->tdg_cpumask)
atomic_set_int(&tdq_idle, tdg->tdg_mask);
tdq->tdq_lowpri = td->td_priority;
#endif
return (td);
}
/*
* 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;
ctd = curthread;
pri = td->td_priority;
cpri = ctd->td_priority;
if (td->td_priority < ctd->td_priority)
curthread->td_flags |= TDF_NEEDRESCHED;
if (panicstr != NULL || pri >= cpri || cold || TD_IS_INHIBITED(ctd))
return;
/*
* Always preempt IDLE threads. Otherwise only if the preempting
* thread is an ithread.
*/
if (pri > preempt_thresh && cpri < PRI_MIN_IDLE)
return;
ctd->td_owepreempt = 1;
return;
}
/*
* Add a thread to a thread queue. Initializes priority, slice, runq, and
* add it to the appropriate queue. This is the internal function called
* when the tdq is predetermined.
*/
void
tdq_add(struct tdq *tdq, struct thread *td, int flags)
{
struct td_sched *ts;
int class;
#ifdef SMP
int cpumask;
#endif
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"));
ts = td->td_sched;
class = PRI_BASE(td->td_pri_class);
TD_SET_RUNQ(td);
if (ts->ts_slice == 0)
ts->ts_slice = sched_slice;
/*
* Pick the run queue based on priority.
*/
if (td->td_priority <= PRI_MAX_REALTIME)
ts->ts_runq = &tdq->tdq_realtime;
else if (td->td_priority <= PRI_MAX_TIMESHARE)
ts->ts_runq = &tdq->tdq_timeshare;
else
ts->ts_runq = &tdq->tdq_idle;
#ifdef SMP
cpumask = 1 << ts->ts_cpu;
/*
* If we had been idle, clear our bit in the group and potentially
* the global bitmap.
*/
if ((class != PRI_IDLE && class != PRI_ITHD) &&
(tdq->tdq_group->tdg_idlemask & cpumask) != 0) {
/*
* Check to see if our group is unidling, and if so, remove it
* from the global idle mask.
*/
if (tdq->tdq_group->tdg_idlemask ==
tdq->tdq_group->tdg_cpumask)
atomic_clear_int(&tdq_idle, tdq->tdq_group->tdg_mask);
/*
* Now remove ourselves from the group specific idle mask.
*/
tdq->tdq_group->tdg_idlemask &= ~cpumask;
}
if (td->td_priority < tdq->tdq_lowpri)
tdq->tdq_lowpri = td->td_priority;
#endif
tdq_runq_add(tdq, ts, flags);
tdq_load_add(tdq, ts);
}
/*
* 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 td_sched *ts;
struct tdq *tdq;
#ifdef SMP
int cpuid;
int cpu;
#endif
CTR5(KTR_SCHED, "sched_add: %p(%s) prio %d by %p(%s)",
td, td->td_name, td->td_priority, curthread,
curthread->td_name);
THREAD_LOCK_ASSERT(td, MA_OWNED);
ts = td->td_sched;
/*
* 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
cpuid = PCPU_GET(cpuid);
/*
* Pick the destination cpu and if it isn't ours transfer to the
* target cpu.
*/
if (td->td_priority <= PRI_MAX_ITHD && THREAD_CAN_MIGRATE(td) &&
curthread->td_intr_nesting_level)
ts->ts_cpu = cpuid;
if (!THREAD_CAN_MIGRATE(td))
cpu = ts->ts_cpu;
else
cpu = sched_pickcpu(ts, flags);
tdq = sched_setcpu(ts, cpu, flags);
tdq_add(tdq, td, flags);
if (cpu != cpuid) {
tdq_notify(ts);
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;
struct td_sched *ts;
CTR5(KTR_SCHED, "sched_rem: %p(%s) prio %d by %p(%s)",
td, td->td_name, td->td_priority, curthread,
curthread->td_name);
ts = td->td_sched;
tdq = TDQ_CPU(ts->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, ts);
tdq_load_rem(tdq, ts);
TD_SET_CAN_RUN(td);
}
/*
* 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(td);
if (ts->ts_ticks) {
int rtick;
sched_pctcpu_update(ts);
/* How many rtick per second ? */
rtick = min(SCHED_TICK_HZ(ts) / SCHED_TICK_SECS, hz);
pctcpu = (FSCALE * ((FSCALE * rtick)/hz)) >> FSHIFT;
}
thread_unlock(td);
return (pctcpu);
}
/*
* 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);
ts = td->td_sched;
if (ts->ts_flags & TSF_BOUND)
sched_unbind(td);
ts->ts_flags |= TSF_BOUND;
#ifdef SMP
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);
#endif
}
/*
* Release a bound thread.
*/
void
sched_unbind(struct thread *td)
{
struct td_sched *ts;
THREAD_LOCK_ASSERT(td, MA_OWNED);
ts = td->td_sched;
if ((ts->ts_flags & TSF_BOUND) == 0)
return;
ts->ts_flags &= ~TSF_BOUND;
#ifdef SMP
sched_unpin();
#endif
}
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);
SCHED_STAT_INC(switch_relinquish);
mi_switch(SW_VOL, NULL);
thread_unlock(td);
}
/*
* Return the total system load.
*/
int
sched_load(void)
{
#ifdef SMP
int total;
int i;
total = 0;
for (i = 0; i <= tdg_maxid; i++)
total += TDQ_GROUP(i)->tdg_load;
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));
}
/*
* The actual idle process.
*/
void
sched_idletd(void *dummy)
{
struct thread *td;
struct tdq *tdq;
td = curthread;
tdq = TDQ_SELF();
mtx_assert(&Giant, MA_NOTOWNED);
/* ULE relies on preemption for idle interruption. */
for (;;) {
#ifdef SMP
if (tdq_idled(tdq))
cpu_idle();
#else
cpu_idle();
#endif
}
}
/*
* 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();
} else {
MPASS(td->td_lock == TDQ_LOCKPTR(tdq));
tdq_load_rem(tdq, td->td_sched);
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;
PCPU_SET(switchtime, cpu_ticks());
PCPU_SET(switchticks, ticks);
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 td_sched *ts;
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);
ts = td->td_sched;
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__);
}
static SYSCTL_NODE(_kern, OID_AUTO, sched, CTLFLAG_RW, 0,
"Scheduler");
SYSCTL_STRING(_kern_sched, OID_AUTO, name, CTLFLAG_RD, "ULE", 0,
"Scheduler name");
SYSCTL_INT(_kern_sched, OID_AUTO, slice, CTLFLAG_RW, &sched_slice, 0,
"Slice size for timeshare threads");
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,"Min priority for preemption, lower priorities have greater precedence");
#ifdef SMP
SYSCTL_INT(_kern_sched, OID_AUTO, pick_pri, CTLFLAG_RW, &pick_pri, 0,
"Pick the target cpu based on priority rather than load.");
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, tryself, CTLFLAG_RW, &tryself, 0, "");
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 frequency in stathz ticks to run the long-term balancer");
SYSCTL_INT(_kern_sched, OID_AUTO, steal_htt, CTLFLAG_RW, &steal_htt, 0,
"Steals work from another hyper-threaded core on idle");
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_INT(_kern_sched, OID_AUTO, topology, CTLFLAG_RD, &topology, 0,
"True when a topology has been specified by the MD code.");
#endif
/* ps compat. All cpu percentages from ULE are weighted. */
static int ccpu = 0;
SYSCTL_INT(_kern, OID_AUTO, ccpu, CTLFLAG_RD, &ccpu, 0, "");
#define KERN_SWITCH_INCLUDE 1
#include "kern/kern_switch.c"
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