/*-
* Copyright (c) 1982, 1986, 1990, 1991, 1993
* The Regents of the University of California. All rights reserved.
* (c) UNIX System Laboratories, Inc.
* All or some portions of this file are derived from material licensed
* to the University of California by American Telephone and Telegraph
* Co. or Unix System Laboratories, Inc. and are reproduced herein with
* the permission of UNIX System Laboratories, Inc.
*
* 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.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
*
* @(#)kern_synch.c 8.9 (Berkeley) 5/19/95
* $FreeBSD$
*/
#include "opt_ddb.h"
#include "opt_ktrace.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/condvar.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/resourcevar.h>
#include <sys/signalvar.h>
#include <sys/smp.h>
#include <sys/sx.h>
#include <sys/sysctl.h>
#include <sys/sysproto.h>
#include <sys/vmmeter.h>
#ifdef DDB
#include <ddb/ddb.h>
#endif
#ifdef KTRACE
#include <sys/uio.h>
#include <sys/ktrace.h>
#endif
#include <machine/cpu.h>
static void sched_setup __P((void *dummy));
SYSINIT(sched_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, sched_setup, NULL)
int hogticks;
int lbolt;
int sched_quantum; /* Roundrobin scheduling quantum in ticks. */
static struct callout loadav_callout;
static struct callout schedcpu_callout;
static struct callout roundrobin_callout;
struct loadavg averunnable =
{ {0, 0, 0}, FSCALE }; /* load average, of runnable procs */
/*
* Constants for averages over 1, 5, and 15 minutes
* when sampling at 5 second intervals.
*/
static fixpt_t cexp[3] = {
0.9200444146293232 * FSCALE, /* exp(-1/12) */
0.9834714538216174 * FSCALE, /* exp(-1/60) */
0.9944598480048967 * FSCALE, /* exp(-1/180) */
};
static void endtsleep __P((void *));
static void loadav __P((void *arg));
static void roundrobin __P((void *arg));
static void schedcpu __P((void *arg));
static int
sysctl_kern_quantum(SYSCTL_HANDLER_ARGS)
{
int error, new_val;
new_val = sched_quantum * tick;
error = sysctl_handle_int(oidp, &new_val, 0, req);
if (error != 0 || req->newptr == NULL)
return (error);
if (new_val < tick)
return (EINVAL);
sched_quantum = new_val / tick;
hogticks = 2 * sched_quantum;
return (0);
}
SYSCTL_PROC(_kern, OID_AUTO, quantum, CTLTYPE_INT|CTLFLAG_RW,
0, sizeof sched_quantum, sysctl_kern_quantum, "I", "");
/*
* Arrange to reschedule if necessary, taking the priorities and
* schedulers into account.
*/
void
maybe_resched(kg)
struct ksegrp *kg;
{
mtx_assert(&sched_lock, MA_OWNED);
if (kg->kg_pri.pri_level < curthread->td_ksegrp->kg_pri.pri_level)
curthread->td_kse->ke_flags |= KEF_NEEDRESCHED;
}
int
roundrobin_interval(void)
{
return (sched_quantum);
}
/*
* Force switch among equal priority processes every 100ms.
* We don't actually need to force a context switch of the current process.
* The act of firing the event triggers a context switch to softclock() and
* then switching back out again which is equivalent to a preemption, thus
* no further work is needed on the local CPU.
*/
/* ARGSUSED */
static void
roundrobin(arg)
void *arg;
{
#ifdef SMP
mtx_lock_spin(&sched_lock);
forward_roundrobin();
mtx_unlock_spin(&sched_lock);
#endif
callout_reset(&roundrobin_callout, sched_quantum, roundrobin, NULL);
}
/*
* Constants for digital decay and forget:
* 90% of (p_estcpu) usage in 5 * loadav time
* 95% of (p_pctcpu) usage in 60 seconds (load insensitive)
* Note that, as ps(1) mentions, this can let percentages
* total over 100% (I've seen 137.9% for 3 processes).
*
* Note that schedclock() updates p_estcpu and p_cpticks asynchronously.
*
* We wish to decay away 90% of p_estcpu in (5 * loadavg) seconds.
* That is, the system wants to compute a value of decay such
* that the following for loop:
* for (i = 0; i < (5 * loadavg); i++)
* p_estcpu *= decay;
* will compute
* p_estcpu *= 0.1;
* for all values of loadavg:
*
* Mathematically this loop can be expressed by saying:
* decay ** (5 * loadavg) ~= .1
*
* The system computes decay as:
* decay = (2 * loadavg) / (2 * loadavg + 1)
*
* We wish to prove that the system's computation of decay
* will always fulfill the equation:
* decay ** (5 * loadavg) ~= .1
*
* If we compute b as:
* b = 2 * loadavg
* then
* decay = b / (b + 1)
*
* We now need to prove two things:
* 1) Given factor ** (5 * loadavg) ~= .1, prove factor == b/(b+1)
* 2) Given b/(b+1) ** power ~= .1, prove power == (5 * loadavg)
*
* Facts:
* For x close to zero, exp(x) =~ 1 + x, since
* exp(x) = 0! + x**1/1! + x**2/2! + ... .
* therefore exp(-1/b) =~ 1 - (1/b) = (b-1)/b.
* For x close to zero, ln(1+x) =~ x, since
* ln(1+x) = x - x**2/2 + x**3/3 - ... -1 < x < 1
* therefore ln(b/(b+1)) = ln(1 - 1/(b+1)) =~ -1/(b+1).
* ln(.1) =~ -2.30
*
* Proof of (1):
* Solve (factor)**(power) =~ .1 given power (5*loadav):
* solving for factor,
* ln(factor) =~ (-2.30/5*loadav), or
* factor =~ exp(-1/((5/2.30)*loadav)) =~ exp(-1/(2*loadav)) =
* exp(-1/b) =~ (b-1)/b =~ b/(b+1). QED
*
* Proof of (2):
* Solve (factor)**(power) =~ .1 given factor == (b/(b+1)):
* solving for power,
* power*ln(b/(b+1)) =~ -2.30, or
* power =~ 2.3 * (b + 1) = 4.6*loadav + 2.3 =~ 5*loadav. QED
*
* Actual power values for the implemented algorithm are as follows:
* loadav: 1 2 3 4
* power: 5.68 10.32 14.94 19.55
*/
/* calculations for digital decay to forget 90% of usage in 5*loadav sec */
#define loadfactor(loadav) (2 * (loadav))
#define decay_cpu(loadfac, cpu) (((loadfac) * (cpu)) / ((loadfac) + FSCALE))
/* decay 95% of `p_pctcpu' in 60 seconds; see CCPU_SHIFT before changing */
static fixpt_t ccpu = 0.95122942450071400909 * FSCALE; /* exp(-1/20) */
SYSCTL_INT(_kern, OID_AUTO, ccpu, CTLFLAG_RD, &ccpu, 0, "");
/* kernel uses `FSCALE', userland (SHOULD) use kern.fscale */
static int fscale __unused = FSCALE;
SYSCTL_INT(_kern, OID_AUTO, fscale, CTLFLAG_RD, 0, FSCALE, "");
/*
* If `ccpu' is not equal to `exp(-1/20)' and you still want to use the
* faster/more-accurate formula, you'll have to estimate CCPU_SHIFT below
* and possibly adjust FSHIFT in "param.h" so that (FSHIFT >= CCPU_SHIFT).
*
* To estimate CCPU_SHIFT for exp(-1/20), the following formula was used:
* 1 - exp(-1/20) ~= 0.0487 ~= 0.0488 == 1 (fixed pt, *11* bits).
*
* If you don't want to bother with the faster/more-accurate formula, you
* can set CCPU_SHIFT to (FSHIFT + 1) which will use a slower/less-accurate
* (more general) method of calculating the %age of CPU used by a process.
*/
#define CCPU_SHIFT 11
/*
* Recompute process priorities, every hz ticks.
* MP-safe, called without the Giant mutex.
*/
/* ARGSUSED */
static void
schedcpu(arg)
void *arg;
{
register fixpt_t loadfac = loadfactor(averunnable.ldavg[0]);
register struct proc *p;
register struct kse *ke;
register struct ksegrp *kg;
register int realstathz;
int awake;
realstathz = stathz ? stathz : hz;
sx_slock(&allproc_lock);
FOREACH_PROC_IN_SYSTEM(p) {
mtx_lock_spin(&sched_lock);
p->p_swtime++;
FOREACH_KSEGRP_IN_PROC(p, kg) {
awake = 0;
FOREACH_KSE_IN_GROUP(kg, ke) {
/*
* Increment time in/out of memory and sleep
* time (if sleeping). We ignore overflow;
* with 16-bit int's (remember them?)
* overflow takes 45 days.
*/
/* XXXKSE */
/* if ((ke->ke_flags & KEF_ONRUNQ) == 0) */
if (p->p_stat == SSLEEP || p->p_stat == SSTOP) {
ke->ke_slptime++;
} else {
ke->ke_slptime = 0;
awake = 1;
}
/*
* pctcpu is only for ps?
* Do it per kse.. and add them up at the end?
* XXXKSE
*/
ke->ke_pctcpu = (ke->ke_pctcpu * ccpu) >> FSHIFT;
/*
* If the kse has been idle the entire second,
* stop recalculating its priority until
* it wakes up.
*/
if (ke->ke_slptime > 1) {
continue;
}
#if (FSHIFT >= CCPU_SHIFT)
ke->ke_pctcpu += (realstathz == 100) ?
((fixpt_t) ke->ke_cpticks) <<
(FSHIFT - CCPU_SHIFT) :
100 * (((fixpt_t) ke->ke_cpticks) <<
(FSHIFT - CCPU_SHIFT)) / realstathz;
#else
ke->ke_pctcpu += ((FSCALE - ccpu) *
(ke->ke_cpticks * FSCALE / realstathz)) >>
FSHIFT;
#endif
ke->ke_cpticks = 0;
} /* end of kse loop */
if (awake == 0) {
kg->kg_slptime++;
} else {
kg->kg_slptime = 0;
}
kg->kg_estcpu = decay_cpu(loadfac, kg->kg_estcpu);
resetpriority(kg);
if (kg->kg_pri.pri_level >= PUSER &&
(p->p_sflag & PS_INMEM)) {
int changedqueue =
((kg->kg_pri.pri_level / RQ_PPQ) !=
(kg->kg_pri.pri_user / RQ_PPQ));
kg->kg_pri.pri_level = kg->kg_pri.pri_user;
FOREACH_KSE_IN_GROUP(kg, ke) {
if ((ke->ke_oncpu == NOCPU) && /* idle */
(p->p_stat == SRUN) && /* XXXKSE */
changedqueue) {
remrunqueue(ke->ke_thread);
setrunqueue(ke->ke_thread);
}
}
}
} /* end of ksegrp loop */
mtx_unlock_spin(&sched_lock);
} /* end of process loop */
sx_sunlock(&allproc_lock);
wakeup((caddr_t)&lbolt);
callout_reset(&schedcpu_callout, hz, schedcpu, NULL);
}
/*
* Recalculate the priority of a process after it has slept for a while.
* For all load averages >= 1 and max p_estcpu of 255, sleeping for at
* least six times the loadfactor will decay p_estcpu to zero.
*/
void
updatepri(td)
register struct thread *td;
{
register struct ksegrp *kg;
register unsigned int newcpu;
register fixpt_t loadfac = loadfactor(averunnable.ldavg[0]);
if (td == NULL)
return;
kg = td->td_ksegrp;
newcpu = kg->kg_estcpu;
if (kg->kg_slptime > 5 * loadfac)
kg->kg_estcpu = 0;
else {
kg->kg_slptime--; /* the first time was done in schedcpu */
while (newcpu && --kg->kg_slptime)
newcpu = decay_cpu(loadfac, newcpu);
kg->kg_estcpu = newcpu;
}
resetpriority(td->td_ksegrp);
}
/*
* We're only looking at 7 bits of the address; everything is
* aligned to 4, lots of things are aligned to greater powers
* of 2. Shift right by 8, i.e. drop the bottom 256 worth.
*/
#define TABLESIZE 128
static TAILQ_HEAD(slpquehead, thread) slpque[TABLESIZE];
#define LOOKUP(x) (((intptr_t)(x) >> 8) & (TABLESIZE - 1))
void
sleepinit(void)
{
int i;
sched_quantum = hz/10;
hogticks = 2 * sched_quantum;
for (i = 0; i < TABLESIZE; i++)
TAILQ_INIT(&slpque[i]);
}
/*
* General sleep call. Suspends the current process until a wakeup is
* performed on the specified identifier. The process will then be made
* runnable with the specified priority. Sleeps at most timo/hz seconds
* (0 means no timeout). If pri includes PCATCH flag, signals are checked
* before and after sleeping, else signals are not checked. Returns 0 if
* awakened, EWOULDBLOCK if the timeout expires. If PCATCH is set and a
* signal needs to be delivered, ERESTART is returned if the current system
* call should be restarted if possible, and EINTR is returned if the system
* call should be interrupted by the signal (return EINTR).
*
* The mutex argument is exited before the caller is suspended, and
* entered before msleep returns. If priority includes the PDROP
* flag the mutex is not entered before returning.
*/
int
msleep(ident, mtx, priority, wmesg, timo)
void *ident;
struct mtx *mtx;
int priority, timo;
const char *wmesg;
{
struct proc *p = curproc;
struct thread *td = curthread;
int sig, catch = priority & PCATCH;
int rval = 0;
WITNESS_SAVE_DECL(mtx);
#ifdef KTRACE
if (p && KTRPOINT(p, KTR_CSW))
ktrcsw(p->p_tracep, 1, 0);
#endif
WITNESS_SLEEP(0, &mtx->mtx_object);
KASSERT(timo != 0 || mtx_owned(&Giant) || mtx != NULL,
("sleeping without a mutex"));
mtx_lock_spin(&sched_lock);
if (cold || panicstr) {
/*
* After a panic, or during autoconfiguration,
* just give interrupts a chance, then just return;
* don't run any other procs or panic below,
* in case this is the idle process and already asleep.
*/
if (mtx != NULL && priority & PDROP)
mtx_unlock_flags(mtx, MTX_NOSWITCH);
mtx_unlock_spin(&sched_lock);
return (0);
}
DROP_GIANT_NOSWITCH();
if (mtx != NULL) {
mtx_assert(mtx, MA_OWNED | MA_NOTRECURSED);
WITNESS_SAVE(&mtx->mtx_object, mtx);
mtx_unlock_flags(mtx, MTX_NOSWITCH);
if (priority & PDROP)
mtx = NULL;
}
KASSERT(p != NULL, ("msleep1"));
KASSERT(ident != NULL && td->td_proc->p_stat == SRUN, ("msleep"));
td->td_wchan = ident;
td->td_wmesg = wmesg;
td->td_kse->ke_slptime = 0; /* XXXKSE */
td->td_ksegrp->kg_slptime = 0;
td->td_ksegrp->kg_pri.pri_level = priority & PRIMASK;
CTR5(KTR_PROC, "msleep: thread %p (pid %d, %s) on %s (%p)",
td, p->p_pid, p->p_comm, wmesg, ident);
TAILQ_INSERT_TAIL(&slpque[LOOKUP(ident)], td, td_slpq);
if (timo)
callout_reset(&td->td_slpcallout, timo, endtsleep, td);
/*
* We put ourselves on the sleep queue and start our timeout
* before calling CURSIG, as we could stop there, and a wakeup
* or a SIGCONT (or both) could occur while we were stopped.
* A SIGCONT would cause us to be marked as SSLEEP
* without resuming us, thus we must be ready for sleep
* when CURSIG is called. If the wakeup happens while we're
* stopped, td->td_wchan will be 0 upon return from CURSIG.
*/
if (catch) {
CTR3(KTR_PROC, "msleep caught: proc %p (pid %d, %s)", p,
p->p_pid, p->p_comm);
td->td_flags |= TDF_SINTR;
mtx_unlock_spin(&sched_lock);
PROC_LOCK(p);
sig = CURSIG(p);
mtx_lock_spin(&sched_lock);
PROC_UNLOCK_NOSWITCH(p);
if (sig != 0) {
if (td->td_wchan != NULL)
unsleep(td);
} else if (td->td_wchan == NULL)
catch = 0;
} else
sig = 0;
if (td->td_wchan != NULL) {
td->td_proc->p_stat = SSLEEP;
p->p_stats->p_ru.ru_nvcsw++;
mi_switch();
}
CTR3(KTR_PROC, "msleep resume: proc %p (pid %d, %s)", td, p->p_pid,
p->p_comm);
KASSERT(td->td_proc->p_stat == SRUN, ("running but not SRUN"));
td->td_flags &= ~TDF_SINTR;
if (td->td_flags & TDF_TIMEOUT) {
td->td_flags &= ~TDF_TIMEOUT;
if (sig == 0)
rval = EWOULDBLOCK;
} else if (td->td_flags & TDF_TIMOFAIL)
td->td_flags &= ~TDF_TIMOFAIL;
else if (timo && callout_stop(&td->td_slpcallout) == 0) {
/*
* This isn't supposed to be pretty. If we are here, then
* the endtsleep() callout is currently executing on another
* CPU and is either spinning on the sched_lock or will be
* soon. If we don't synchronize here, there is a chance
* that this process may msleep() again before the callout
* has a chance to run and the callout may end up waking up
* the wrong msleep(). Yuck.
*/
td->td_flags |= TDF_TIMEOUT;
p->p_stats->p_ru.ru_nivcsw++;
mi_switch();
}
mtx_unlock_spin(&sched_lock);
if (rval == 0 && catch) {
PROC_LOCK(p);
/* XXX: shouldn't we always be calling CURSIG() */
if (sig != 0 || (sig = CURSIG(p))) {
if (SIGISMEMBER(p->p_sigacts->ps_sigintr, sig))
rval = EINTR;
else
rval = ERESTART;
}
PROC_UNLOCK(p);
}
PICKUP_GIANT();
#ifdef KTRACE
mtx_lock(&Giant);
if (KTRPOINT(p, KTR_CSW))
ktrcsw(p->p_tracep, 0, 0);
mtx_unlock(&Giant);
#endif
if (mtx != NULL) {
mtx_lock(mtx);
WITNESS_RESTORE(&mtx->mtx_object, mtx);
}
return (rval);
}
/*
* Implement timeout for msleep()
*
* If process hasn't been awakened (wchan non-zero),
* set timeout flag and undo the sleep. If proc
* is stopped, just unsleep so it will remain stopped.
* MP-safe, called without the Giant mutex.
*/
static void
endtsleep(arg)
void *arg;
{
register struct thread *td = arg;
CTR3(KTR_PROC, "endtsleep: thread %p (pid %d, %s)", td, td->td_proc->p_pid,
td->td_proc->p_comm);
mtx_lock_spin(&sched_lock);
/*
* This is the other half of the synchronization with msleep()
* described above. If the PS_TIMEOUT flag is set, we lost the
* race and just need to put the process back on the runqueue.
*/
if ((td->td_flags & TDF_TIMEOUT) != 0) {
td->td_flags &= ~TDF_TIMEOUT;
setrunqueue(td);
} else if (td->td_wchan != NULL) {
if (td->td_proc->p_stat == SSLEEP) /* XXXKSE */
setrunnable(td);
else
unsleep(td);
td->td_flags |= TDF_TIMEOUT;
} else {
td->td_flags |= TDF_TIMOFAIL;
}
mtx_unlock_spin(&sched_lock);
}
/*
* Remove a process from its wait queue
*/
void
unsleep(struct thread *td)
{
mtx_lock_spin(&sched_lock);
if (td->td_wchan != NULL) {
TAILQ_REMOVE(&slpque[LOOKUP(td->td_wchan)], td, td_slpq);
td->td_wchan = NULL;
}
mtx_unlock_spin(&sched_lock);
}
/*
* Make all processes sleeping on the specified identifier runnable.
*/
void
wakeup(ident)
register void *ident;
{
register struct slpquehead *qp;
register struct thread *td;
struct proc *p;
mtx_lock_spin(&sched_lock);
qp = &slpque[LOOKUP(ident)];
restart:
TAILQ_FOREACH(td, qp, td_slpq) {
p = td->td_proc;
if (td->td_wchan == ident) {
TAILQ_REMOVE(qp, td, td_slpq);
td->td_wchan = NULL;
if (td->td_proc->p_stat == SSLEEP) {
/* OPTIMIZED EXPANSION OF setrunnable(p); */
CTR3(KTR_PROC, "wakeup: thread %p (pid %d, %s)",
td, p->p_pid, p->p_comm);
if (td->td_ksegrp->kg_slptime > 1)
updatepri(td);
td->td_ksegrp->kg_slptime = 0;
td->td_kse->ke_slptime = 0;
td->td_proc->p_stat = SRUN;
if (p->p_sflag & PS_INMEM) {
setrunqueue(td);
maybe_resched(td->td_ksegrp);
} else {
p->p_sflag |= PS_SWAPINREQ;
wakeup((caddr_t)&proc0);
}
/* END INLINE EXPANSION */
goto restart;
}
}
}
mtx_unlock_spin(&sched_lock);
}
/*
* Make a process sleeping on the specified identifier runnable.
* May wake more than one process if a target process is currently
* swapped out.
*/
void
wakeup_one(ident)
register void *ident;
{
register struct slpquehead *qp;
register struct thread *td;
register struct proc *p;
mtx_lock_spin(&sched_lock);
qp = &slpque[LOOKUP(ident)];
TAILQ_FOREACH(td, qp, td_slpq) {
p = td->td_proc;
if (td->td_wchan == ident) {
TAILQ_REMOVE(qp, td, td_slpq);
td->td_wchan = NULL;
if (td->td_proc->p_stat == SSLEEP) {
/* OPTIMIZED EXPANSION OF setrunnable(p); */
CTR3(KTR_PROC, "wakeup1: proc %p (pid %d, %s)",
p, p->p_pid, p->p_comm);
if (td->td_ksegrp->kg_slptime > 1)
updatepri(td);
td->td_ksegrp->kg_slptime = 0;
td->td_kse->ke_slptime = 0;
td->td_proc->p_stat = SRUN;
if (p->p_sflag & PS_INMEM) {
setrunqueue(td);
maybe_resched(td->td_ksegrp);
break;
} else {
p->p_sflag |= PS_SWAPINREQ;
wakeup((caddr_t)&proc0);
}
/* END INLINE EXPANSION */
}
}
}
mtx_unlock_spin(&sched_lock);
}
/*
* The machine independent parts of mi_switch().
*/
void
mi_switch()
{
struct timeval new_switchtime;
struct thread *td = curthread; /* XXX */
register struct proc *p = td->td_proc; /* XXX */
#if 0
register struct rlimit *rlim;
#endif
critical_t sched_crit;
u_int sched_nest;
mtx_assert(&sched_lock, MA_OWNED | MA_NOTRECURSED);
#ifdef INVARIANTS
if (p->p_stat != SMTX && p->p_stat != SRUN)
mtx_assert(&Giant, MA_NOTOWNED);
#endif
/*
* Compute the amount of time during which the current
* process was running, and add that to its total so far.
*/
microuptime(&new_switchtime);
if (timevalcmp(&new_switchtime, PCPU_PTR(switchtime), <)) {
#if 0
/* XXX: This doesn't play well with sched_lock right now. */
printf("microuptime() went backwards (%ld.%06ld -> %ld.%06ld)\n",
PCPU_GET(switchtime.tv_sec), PCPU_GET(switchtime.tv_usec),
new_switchtime.tv_sec, new_switchtime.tv_usec);
#endif
new_switchtime = PCPU_GET(switchtime);
} else {
p->p_runtime += (new_switchtime.tv_usec - PCPU_GET(switchtime.tv_usec)) +
(new_switchtime.tv_sec - PCPU_GET(switchtime.tv_sec)) *
(int64_t)1000000;
}
#ifdef DDB
/*
* Don't perform context switches from the debugger.
*/
if (db_active) {
mtx_unlock_spin(&sched_lock);
db_error("Context switches not allowed in the debugger.");
}
#endif
#if 0
/*
* Check if the process exceeds its cpu resource allocation.
* If over max, kill it.
*
* XXX drop sched_lock, pickup Giant
*/
if (p->p_stat != SZOMB && p->p_limit->p_cpulimit != RLIM_INFINITY &&
p->p_runtime > p->p_limit->p_cpulimit) {
rlim = &p->p_rlimit[RLIMIT_CPU];
if (p->p_runtime / (rlim_t)1000000 >= rlim->rlim_max) {
mtx_unlock_spin(&sched_lock);
PROC_LOCK(p);
killproc(p, "exceeded maximum CPU limit");
mtx_lock_spin(&sched_lock);
PROC_UNLOCK_NOSWITCH(p);
} else {
mtx_unlock_spin(&sched_lock);
PROC_LOCK(p);
psignal(p, SIGXCPU);
mtx_lock_spin(&sched_lock);
PROC_UNLOCK_NOSWITCH(p);
if (rlim->rlim_cur < rlim->rlim_max) {
/* XXX: we should make a private copy */
rlim->rlim_cur += 5;
}
}
}
#endif
/*
* Pick a new current process and record its start time.
*/
cnt.v_swtch++;
PCPU_SET(switchtime, new_switchtime);
CTR3(KTR_PROC, "mi_switch: old proc %p (pid %d, %s)", p, p->p_pid,
p->p_comm);
sched_crit = sched_lock.mtx_savecrit;
sched_nest = sched_lock.mtx_recurse;
td->td_lastcpu = td->td_kse->ke_oncpu;
td->td_kse->ke_oncpu = NOCPU;
td->td_kse->ke_flags &= ~KEF_NEEDRESCHED;
cpu_switch();
td->td_kse->ke_oncpu = PCPU_GET(cpuid);
sched_lock.mtx_savecrit = sched_crit;
sched_lock.mtx_recurse = sched_nest;
sched_lock.mtx_lock = (uintptr_t)td;
CTR3(KTR_PROC, "mi_switch: new proc %p (pid %d, %s)", p, p->p_pid,
p->p_comm);
if (PCPU_GET(switchtime.tv_sec) == 0)
microuptime(PCPU_PTR(switchtime));
PCPU_SET(switchticks, ticks);
}
/*
* Change process state to be runnable,
* placing it on the run queue if it is in memory,
* and awakening the swapper if it isn't in memory.
*/
void
setrunnable(struct thread *td)
{
struct proc *p = td->td_proc;
mtx_lock_spin(&sched_lock);
switch (p->p_stat) {
case SZOMB: /* not a thread flag XXXKSE */
panic("setrunnable(1)");
}
switch (td->td_proc->p_stat) {
case 0:
case SRUN:
case SWAIT:
default:
panic("setrunnable(2)");
case SSTOP:
case SSLEEP: /* e.g. when sending signals */
if (td->td_flags & TDF_CVWAITQ)
cv_waitq_remove(td);
else
unsleep(td);
break;
case SIDL:
break;
}
td->td_proc->p_stat = SRUN;
if (td->td_ksegrp->kg_slptime > 1)
updatepri(td);
td->td_ksegrp->kg_slptime = 0;
td->td_kse->ke_slptime = 0;
if ((p->p_sflag & PS_INMEM) == 0) {
p->p_sflag |= PS_SWAPINREQ;
wakeup((caddr_t)&proc0);
} else {
setrunqueue(td);
maybe_resched(td->td_ksegrp);
}
mtx_unlock_spin(&sched_lock);
}
/*
* Compute the priority of a process when running in user mode.
* Arrange to reschedule if the resulting priority is better
* than that of the current process.
*/
void
resetpriority(kg)
register struct ksegrp *kg;
{
register unsigned int newpriority;
mtx_lock_spin(&sched_lock);
if (kg->kg_pri.pri_class == PRI_TIMESHARE) {
newpriority = PUSER + kg->kg_estcpu / INVERSE_ESTCPU_WEIGHT +
NICE_WEIGHT * (kg->kg_nice - PRIO_MIN);
newpriority = min(max(newpriority, PRI_MIN_TIMESHARE),
PRI_MAX_TIMESHARE);
kg->kg_pri.pri_user = newpriority;
}
maybe_resched(kg);
mtx_unlock_spin(&sched_lock);
}
/*
* Compute a tenex style load average of a quantity on
* 1, 5 and 15 minute intervals.
* XXXKSE Needs complete rewrite when correct info is available.
* Completely Bogus.. only works with 1:1 (but compiles ok now :-)
*/
static void
loadav(void *arg)
{
int i, nrun;
struct loadavg *avg;
struct proc *p;
struct ksegrp *kg;
avg = &averunnable;
sx_slock(&allproc_lock);
nrun = 0;
FOREACH_PROC_IN_SYSTEM(p) {
FOREACH_KSEGRP_IN_PROC(p, kg) {
switch (p->p_stat) {
case SRUN:
if ((p->p_flag & P_NOLOAD) != 0)
goto nextproc;
/* FALLTHROUGH */
case SIDL:
nrun++;
}
nextproc:
}
}
sx_sunlock(&allproc_lock);
for (i = 0; i < 3; i++)
avg->ldavg[i] = (cexp[i] * avg->ldavg[i] +
nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT;
/*
* Schedule the next update to occur after 5 seconds, but add a
* random variation to avoid synchronisation with processes that
* run at regular intervals.
*/
callout_reset(&loadav_callout, hz * 4 + (int)(random() % (hz * 2 + 1)),
loadav, NULL);
}
/* ARGSUSED */
static void
sched_setup(dummy)
void *dummy;
{
callout_init(&schedcpu_callout, 1);
callout_init(&roundrobin_callout, 0);
callout_init(&loadav_callout, 0);
/* Kick off timeout driven events by calling first time. */
roundrobin(NULL);
schedcpu(NULL);
loadav(NULL);
}
/*
* We adjust the priority of the current process. The priority of
* a process gets worse as it accumulates CPU time. The cpu usage
* estimator (p_estcpu) is increased here. resetpriority() will
* compute a different priority each time p_estcpu increases by
* INVERSE_ESTCPU_WEIGHT
* (until MAXPRI is reached). The cpu usage estimator ramps up
* quite quickly when the process is running (linearly), and decays
* away exponentially, at a rate which is proportionally slower when
* the system is busy. The basic principle is that the system will
* 90% forget that the process used a lot of CPU time in 5 * loadav
* seconds. This causes the system to favor processes which haven't
* run much recently, and to round-robin among other processes.
*/
void
schedclock(td)
struct thread *td;
{
struct kse *ke = td->td_kse;
struct ksegrp *kg = td->td_ksegrp;
if (td) {
ke->ke_cpticks++;
kg->kg_estcpu = ESTCPULIM(kg->kg_estcpu + 1);
if ((kg->kg_estcpu % INVERSE_ESTCPU_WEIGHT) == 0) {
resetpriority(td->td_ksegrp);
if (kg->kg_pri.pri_level >= PUSER)
kg->kg_pri.pri_level = kg->kg_pri.pri_user;
}
} else {
panic("schedclock");
}
}
/*
* General purpose yield system call
*/
int
yield(struct thread *td, struct yield_args *uap)
{
struct ksegrp *kg = td->td_ksegrp;
mtx_assert(&Giant, MA_NOTOWNED);
mtx_lock_spin(&sched_lock);
kg->kg_pri.pri_level = PRI_MAX_TIMESHARE;
setrunqueue(td);
kg->kg_proc->p_stats->p_ru.ru_nvcsw++;
mi_switch();
mtx_unlock_spin(&sched_lock);
td->td_retval[0] = 0;
return (0);
}