542 lines
14 KiB
C
542 lines
14 KiB
C
/*-
|
|
* Copyright (c) 2001 Jake Burkholder <jake@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, 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 AND CONTRIBUTORS ``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 OR CONTRIBUTORS 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.
|
|
*/
|
|
|
|
|
|
#include <sys/cdefs.h>
|
|
__FBSDID("$FreeBSD$");
|
|
|
|
#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/queue.h>
|
|
#include <sys/sched.h>
|
|
#include <sys/smp.h>
|
|
#include <sys/sysctl.h>
|
|
|
|
#include <machine/cpu.h>
|
|
|
|
/* Uncomment this to enable logging of critical_enter/exit. */
|
|
#if 0
|
|
#define KTR_CRITICAL KTR_SCHED
|
|
#else
|
|
#define KTR_CRITICAL 0
|
|
#endif
|
|
|
|
#ifdef FULL_PREEMPTION
|
|
#ifndef PREEMPTION
|
|
#error "The FULL_PREEMPTION option requires the PREEMPTION option"
|
|
#endif
|
|
#endif
|
|
|
|
CTASSERT((RQB_BPW * RQB_LEN) == RQ_NQS);
|
|
|
|
/*
|
|
* kern.sched.preemption allows user space to determine if preemption support
|
|
* is compiled in or not. It is not currently a boot or runtime flag that
|
|
* can be changed.
|
|
*/
|
|
#ifdef PREEMPTION
|
|
static int kern_sched_preemption = 1;
|
|
#else
|
|
static int kern_sched_preemption = 0;
|
|
#endif
|
|
SYSCTL_INT(_kern_sched, OID_AUTO, preemption, CTLFLAG_RD,
|
|
&kern_sched_preemption, 0, "Kernel preemption enabled");
|
|
|
|
/*
|
|
* Support for scheduler stats exported via kern.sched.stats. All stats may
|
|
* be reset with kern.sched.stats.reset = 1. Stats may be defined elsewhere
|
|
* with SCHED_STAT_DEFINE().
|
|
*/
|
|
#ifdef SCHED_STATS
|
|
SYSCTL_NODE(_kern_sched, OID_AUTO, stats, CTLFLAG_RW, 0, "switch stats");
|
|
|
|
/* Switch reasons from mi_switch(). */
|
|
DPCPU_DEFINE(long, sched_switch_stats[SWT_COUNT]);
|
|
SCHED_STAT_DEFINE_VAR(uncategorized,
|
|
&DPCPU_NAME(sched_switch_stats[SWT_NONE]), "");
|
|
SCHED_STAT_DEFINE_VAR(preempt,
|
|
&DPCPU_NAME(sched_switch_stats[SWT_PREEMPT]), "");
|
|
SCHED_STAT_DEFINE_VAR(owepreempt,
|
|
&DPCPU_NAME(sched_switch_stats[SWT_OWEPREEMPT]), "");
|
|
SCHED_STAT_DEFINE_VAR(turnstile,
|
|
&DPCPU_NAME(sched_switch_stats[SWT_TURNSTILE]), "");
|
|
SCHED_STAT_DEFINE_VAR(sleepq,
|
|
&DPCPU_NAME(sched_switch_stats[SWT_SLEEPQ]), "");
|
|
SCHED_STAT_DEFINE_VAR(sleepqtimo,
|
|
&DPCPU_NAME(sched_switch_stats[SWT_SLEEPQTIMO]), "");
|
|
SCHED_STAT_DEFINE_VAR(relinquish,
|
|
&DPCPU_NAME(sched_switch_stats[SWT_RELINQUISH]), "");
|
|
SCHED_STAT_DEFINE_VAR(needresched,
|
|
&DPCPU_NAME(sched_switch_stats[SWT_NEEDRESCHED]), "");
|
|
SCHED_STAT_DEFINE_VAR(idle,
|
|
&DPCPU_NAME(sched_switch_stats[SWT_IDLE]), "");
|
|
SCHED_STAT_DEFINE_VAR(iwait,
|
|
&DPCPU_NAME(sched_switch_stats[SWT_IWAIT]), "");
|
|
SCHED_STAT_DEFINE_VAR(suspend,
|
|
&DPCPU_NAME(sched_switch_stats[SWT_SUSPEND]), "");
|
|
SCHED_STAT_DEFINE_VAR(remotepreempt,
|
|
&DPCPU_NAME(sched_switch_stats[SWT_REMOTEPREEMPT]), "");
|
|
SCHED_STAT_DEFINE_VAR(remotewakeidle,
|
|
&DPCPU_NAME(sched_switch_stats[SWT_REMOTEWAKEIDLE]), "");
|
|
|
|
static int
|
|
sysctl_stats_reset(SYSCTL_HANDLER_ARGS)
|
|
{
|
|
struct sysctl_oid *p;
|
|
uintptr_t counter;
|
|
int error;
|
|
int val;
|
|
int i;
|
|
|
|
val = 0;
|
|
error = sysctl_handle_int(oidp, &val, 0, req);
|
|
if (error != 0 || req->newptr == NULL)
|
|
return (error);
|
|
if (val == 0)
|
|
return (0);
|
|
/*
|
|
* Traverse the list of children of _kern_sched_stats and reset each
|
|
* to 0. Skip the reset entry.
|
|
*/
|
|
SLIST_FOREACH(p, oidp->oid_parent, oid_link) {
|
|
if (p == oidp || p->oid_arg1 == NULL)
|
|
continue;
|
|
counter = (uintptr_t)p->oid_arg1;
|
|
CPU_FOREACH(i) {
|
|
*(long *)(dpcpu_off[i] + counter) = 0;
|
|
}
|
|
}
|
|
return (0);
|
|
}
|
|
|
|
SYSCTL_PROC(_kern_sched_stats, OID_AUTO, reset, CTLTYPE_INT | CTLFLAG_WR, NULL,
|
|
0, sysctl_stats_reset, "I", "Reset scheduler statistics");
|
|
#endif
|
|
|
|
/************************************************************************
|
|
* Functions that manipulate runnability from a thread perspective. *
|
|
************************************************************************/
|
|
/*
|
|
* Select the thread that will be run next.
|
|
*/
|
|
|
|
static __noinline struct thread *
|
|
choosethread_panic(struct thread *td)
|
|
{
|
|
|
|
/*
|
|
* If we are in panic, only allow system threads,
|
|
* plus the one we are running in, to be run.
|
|
*/
|
|
retry:
|
|
if (((td->td_proc->p_flag & P_SYSTEM) == 0 &&
|
|
(td->td_flags & TDF_INPANIC) == 0)) {
|
|
/* note that it is no longer on the run queue */
|
|
TD_SET_CAN_RUN(td);
|
|
td = sched_choose();
|
|
goto retry;
|
|
}
|
|
|
|
TD_SET_RUNNING(td);
|
|
return (td);
|
|
}
|
|
|
|
struct thread *
|
|
choosethread(void)
|
|
{
|
|
struct thread *td;
|
|
|
|
td = sched_choose();
|
|
|
|
if (__predict_false(panicstr != NULL))
|
|
return (choosethread_panic(td));
|
|
|
|
TD_SET_RUNNING(td);
|
|
return (td);
|
|
}
|
|
|
|
/*
|
|
* Kernel thread preemption implementation. Critical sections mark
|
|
* regions of code in which preemptions are not allowed.
|
|
*
|
|
* It might seem a good idea to inline critical_enter() but, in order
|
|
* to prevent instructions reordering by the compiler, a __compiler_membar()
|
|
* would have to be used here (the same as sched_pin()). The performance
|
|
* penalty imposed by the membar could, then, produce slower code than
|
|
* the function call itself, for most cases.
|
|
*/
|
|
void
|
|
critical_enter(void)
|
|
{
|
|
struct thread *td;
|
|
|
|
td = curthread;
|
|
td->td_critnest++;
|
|
CTR4(KTR_CRITICAL, "critical_enter by thread %p (%ld, %s) to %d", td,
|
|
(long)td->td_proc->p_pid, td->td_name, td->td_critnest);
|
|
}
|
|
|
|
void
|
|
critical_exit(void)
|
|
{
|
|
struct thread *td;
|
|
int flags;
|
|
|
|
td = curthread;
|
|
KASSERT(td->td_critnest != 0,
|
|
("critical_exit: td_critnest == 0"));
|
|
|
|
if (td->td_critnest == 1) {
|
|
td->td_critnest = 0;
|
|
|
|
/*
|
|
* Interrupt handlers execute critical_exit() on
|
|
* leave, and td_owepreempt may be left set by an
|
|
* interrupt handler only when td_critnest > 0. If we
|
|
* are decrementing td_critnest from 1 to 0, read
|
|
* td_owepreempt after decrementing, to not miss the
|
|
* preempt. Disallow compiler to reorder operations.
|
|
*/
|
|
__compiler_membar();
|
|
if (td->td_owepreempt && !kdb_active) {
|
|
/*
|
|
* Microoptimization: we committed to switch,
|
|
* disable preemption in interrupt handlers
|
|
* while spinning for the thread lock.
|
|
*/
|
|
td->td_critnest = 1;
|
|
thread_lock(td);
|
|
td->td_critnest--;
|
|
flags = SW_INVOL | SW_PREEMPT;
|
|
if (TD_IS_IDLETHREAD(td))
|
|
flags |= SWT_IDLE;
|
|
else
|
|
flags |= SWT_OWEPREEMPT;
|
|
mi_switch(flags, NULL);
|
|
thread_unlock(td);
|
|
}
|
|
} else
|
|
td->td_critnest--;
|
|
|
|
CTR4(KTR_CRITICAL, "critical_exit by thread %p (%ld, %s) to %d", td,
|
|
(long)td->td_proc->p_pid, td->td_name, td->td_critnest);
|
|
}
|
|
|
|
/************************************************************************
|
|
* SYSTEM RUN QUEUE manipulations and tests *
|
|
************************************************************************/
|
|
/*
|
|
* Initialize a run structure.
|
|
*/
|
|
void
|
|
runq_init(struct runq *rq)
|
|
{
|
|
int i;
|
|
|
|
bzero(rq, sizeof *rq);
|
|
for (i = 0; i < RQ_NQS; i++)
|
|
TAILQ_INIT(&rq->rq_queues[i]);
|
|
}
|
|
|
|
/*
|
|
* Clear the status bit of the queue corresponding to priority level pri,
|
|
* indicating that it is empty.
|
|
*/
|
|
static __inline void
|
|
runq_clrbit(struct runq *rq, int pri)
|
|
{
|
|
struct rqbits *rqb;
|
|
|
|
rqb = &rq->rq_status;
|
|
CTR4(KTR_RUNQ, "runq_clrbit: bits=%#x %#x bit=%#x word=%d",
|
|
rqb->rqb_bits[RQB_WORD(pri)],
|
|
rqb->rqb_bits[RQB_WORD(pri)] & ~RQB_BIT(pri),
|
|
RQB_BIT(pri), RQB_WORD(pri));
|
|
rqb->rqb_bits[RQB_WORD(pri)] &= ~RQB_BIT(pri);
|
|
}
|
|
|
|
/*
|
|
* Find the index of the first non-empty run queue. This is done by
|
|
* scanning the status bits, a set bit indicates a non-empty queue.
|
|
*/
|
|
static __inline int
|
|
runq_findbit(struct runq *rq)
|
|
{
|
|
struct rqbits *rqb;
|
|
int pri;
|
|
int i;
|
|
|
|
rqb = &rq->rq_status;
|
|
for (i = 0; i < RQB_LEN; i++)
|
|
if (rqb->rqb_bits[i]) {
|
|
pri = RQB_FFS(rqb->rqb_bits[i]) + (i << RQB_L2BPW);
|
|
CTR3(KTR_RUNQ, "runq_findbit: bits=%#x i=%d pri=%d",
|
|
rqb->rqb_bits[i], i, pri);
|
|
return (pri);
|
|
}
|
|
|
|
return (-1);
|
|
}
|
|
|
|
static __inline int
|
|
runq_findbit_from(struct runq *rq, u_char pri)
|
|
{
|
|
struct rqbits *rqb;
|
|
rqb_word_t mask;
|
|
int i;
|
|
|
|
/*
|
|
* Set the mask for the first word so we ignore priorities before 'pri'.
|
|
*/
|
|
mask = (rqb_word_t)-1 << (pri & (RQB_BPW - 1));
|
|
rqb = &rq->rq_status;
|
|
again:
|
|
for (i = RQB_WORD(pri); i < RQB_LEN; mask = -1, i++) {
|
|
mask = rqb->rqb_bits[i] & mask;
|
|
if (mask == 0)
|
|
continue;
|
|
pri = RQB_FFS(mask) + (i << RQB_L2BPW);
|
|
CTR3(KTR_RUNQ, "runq_findbit_from: bits=%#x i=%d pri=%d",
|
|
mask, i, pri);
|
|
return (pri);
|
|
}
|
|
if (pri == 0)
|
|
return (-1);
|
|
/*
|
|
* Wrap back around to the beginning of the list just once so we
|
|
* scan the whole thing.
|
|
*/
|
|
pri = 0;
|
|
goto again;
|
|
}
|
|
|
|
/*
|
|
* Set the status bit of the queue corresponding to priority level pri,
|
|
* indicating that it is non-empty.
|
|
*/
|
|
static __inline void
|
|
runq_setbit(struct runq *rq, int pri)
|
|
{
|
|
struct rqbits *rqb;
|
|
|
|
rqb = &rq->rq_status;
|
|
CTR4(KTR_RUNQ, "runq_setbit: bits=%#x %#x bit=%#x word=%d",
|
|
rqb->rqb_bits[RQB_WORD(pri)],
|
|
rqb->rqb_bits[RQB_WORD(pri)] | RQB_BIT(pri),
|
|
RQB_BIT(pri), RQB_WORD(pri));
|
|
rqb->rqb_bits[RQB_WORD(pri)] |= RQB_BIT(pri);
|
|
}
|
|
|
|
/*
|
|
* Add the thread to the queue specified by its priority, and set the
|
|
* corresponding status bit.
|
|
*/
|
|
void
|
|
runq_add(struct runq *rq, struct thread *td, int flags)
|
|
{
|
|
struct rqhead *rqh;
|
|
int pri;
|
|
|
|
pri = td->td_priority / RQ_PPQ;
|
|
td->td_rqindex = pri;
|
|
runq_setbit(rq, pri);
|
|
rqh = &rq->rq_queues[pri];
|
|
CTR4(KTR_RUNQ, "runq_add: td=%p pri=%d %d rqh=%p",
|
|
td, td->td_priority, pri, rqh);
|
|
if (flags & SRQ_PREEMPTED) {
|
|
TAILQ_INSERT_HEAD(rqh, td, td_runq);
|
|
} else {
|
|
TAILQ_INSERT_TAIL(rqh, td, td_runq);
|
|
}
|
|
}
|
|
|
|
void
|
|
runq_add_pri(struct runq *rq, struct thread *td, u_char pri, int flags)
|
|
{
|
|
struct rqhead *rqh;
|
|
|
|
KASSERT(pri < RQ_NQS, ("runq_add_pri: %d out of range", pri));
|
|
td->td_rqindex = pri;
|
|
runq_setbit(rq, pri);
|
|
rqh = &rq->rq_queues[pri];
|
|
CTR4(KTR_RUNQ, "runq_add_pri: td=%p pri=%d idx=%d rqh=%p",
|
|
td, td->td_priority, pri, rqh);
|
|
if (flags & SRQ_PREEMPTED) {
|
|
TAILQ_INSERT_HEAD(rqh, td, td_runq);
|
|
} else {
|
|
TAILQ_INSERT_TAIL(rqh, td, td_runq);
|
|
}
|
|
}
|
|
/*
|
|
* Return true if there are runnable processes of any priority on the run
|
|
* queue, false otherwise. Has no side effects, does not modify the run
|
|
* queue structure.
|
|
*/
|
|
int
|
|
runq_check(struct runq *rq)
|
|
{
|
|
struct rqbits *rqb;
|
|
int i;
|
|
|
|
rqb = &rq->rq_status;
|
|
for (i = 0; i < RQB_LEN; i++)
|
|
if (rqb->rqb_bits[i]) {
|
|
CTR2(KTR_RUNQ, "runq_check: bits=%#x i=%d",
|
|
rqb->rqb_bits[i], i);
|
|
return (1);
|
|
}
|
|
CTR0(KTR_RUNQ, "runq_check: empty");
|
|
|
|
return (0);
|
|
}
|
|
|
|
/*
|
|
* Find the highest priority process on the run queue.
|
|
*/
|
|
struct thread *
|
|
runq_choose_fuzz(struct runq *rq, int fuzz)
|
|
{
|
|
struct rqhead *rqh;
|
|
struct thread *td;
|
|
int pri;
|
|
|
|
while ((pri = runq_findbit(rq)) != -1) {
|
|
rqh = &rq->rq_queues[pri];
|
|
/* fuzz == 1 is normal.. 0 or less are ignored */
|
|
if (fuzz > 1) {
|
|
/*
|
|
* In the first couple of entries, check if
|
|
* there is one for our CPU as a preference.
|
|
*/
|
|
int count = fuzz;
|
|
int cpu = PCPU_GET(cpuid);
|
|
struct thread *td2;
|
|
td2 = td = TAILQ_FIRST(rqh);
|
|
|
|
while (count-- && td2) {
|
|
if (td2->td_lastcpu == cpu) {
|
|
td = td2;
|
|
break;
|
|
}
|
|
td2 = TAILQ_NEXT(td2, td_runq);
|
|
}
|
|
} else
|
|
td = TAILQ_FIRST(rqh);
|
|
KASSERT(td != NULL, ("runq_choose_fuzz: no proc on busy queue"));
|
|
CTR3(KTR_RUNQ,
|
|
"runq_choose_fuzz: pri=%d thread=%p rqh=%p", pri, td, rqh);
|
|
return (td);
|
|
}
|
|
CTR1(KTR_RUNQ, "runq_choose_fuzz: idleproc pri=%d", pri);
|
|
|
|
return (NULL);
|
|
}
|
|
|
|
/*
|
|
* Find the highest priority process on the run queue.
|
|
*/
|
|
struct thread *
|
|
runq_choose(struct runq *rq)
|
|
{
|
|
struct rqhead *rqh;
|
|
struct thread *td;
|
|
int pri;
|
|
|
|
while ((pri = runq_findbit(rq)) != -1) {
|
|
rqh = &rq->rq_queues[pri];
|
|
td = TAILQ_FIRST(rqh);
|
|
KASSERT(td != NULL, ("runq_choose: no thread on busy queue"));
|
|
CTR3(KTR_RUNQ,
|
|
"runq_choose: pri=%d thread=%p rqh=%p", pri, td, rqh);
|
|
return (td);
|
|
}
|
|
CTR1(KTR_RUNQ, "runq_choose: idlethread pri=%d", pri);
|
|
|
|
return (NULL);
|
|
}
|
|
|
|
struct thread *
|
|
runq_choose_from(struct runq *rq, u_char idx)
|
|
{
|
|
struct rqhead *rqh;
|
|
struct thread *td;
|
|
int pri;
|
|
|
|
if ((pri = runq_findbit_from(rq, idx)) != -1) {
|
|
rqh = &rq->rq_queues[pri];
|
|
td = TAILQ_FIRST(rqh);
|
|
KASSERT(td != NULL, ("runq_choose: no thread on busy queue"));
|
|
CTR4(KTR_RUNQ,
|
|
"runq_choose_from: pri=%d thread=%p idx=%d rqh=%p",
|
|
pri, td, td->td_rqindex, rqh);
|
|
return (td);
|
|
}
|
|
CTR1(KTR_RUNQ, "runq_choose_from: idlethread pri=%d", pri);
|
|
|
|
return (NULL);
|
|
}
|
|
/*
|
|
* Remove the thread from the queue specified by its priority, and clear the
|
|
* corresponding status bit if the queue becomes empty.
|
|
* Caller must set state afterwards.
|
|
*/
|
|
void
|
|
runq_remove(struct runq *rq, struct thread *td)
|
|
{
|
|
|
|
runq_remove_idx(rq, td, NULL);
|
|
}
|
|
|
|
void
|
|
runq_remove_idx(struct runq *rq, struct thread *td, u_char *idx)
|
|
{
|
|
struct rqhead *rqh;
|
|
u_char pri;
|
|
|
|
KASSERT(td->td_flags & TDF_INMEM,
|
|
("runq_remove_idx: thread swapped out"));
|
|
pri = td->td_rqindex;
|
|
KASSERT(pri < RQ_NQS, ("runq_remove_idx: Invalid index %d\n", pri));
|
|
rqh = &rq->rq_queues[pri];
|
|
CTR4(KTR_RUNQ, "runq_remove_idx: td=%p, pri=%d %d rqh=%p",
|
|
td, td->td_priority, pri, rqh);
|
|
TAILQ_REMOVE(rqh, td, td_runq);
|
|
if (TAILQ_EMPTY(rqh)) {
|
|
CTR0(KTR_RUNQ, "runq_remove_idx: empty");
|
|
runq_clrbit(rq, pri);
|
|
if (idx != NULL && *idx == pri)
|
|
*idx = (pri + 1) % RQ_NQS;
|
|
}
|
|
}
|