/*- * 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: src/sys/kern/kern_synch.c,v 1.87.2.6 2002/10/13 07:29:53 kbyanc Exp $ * $DragonFly: src/sys/kern/kern_synch.c,v 1.8 2003/06/25 03:55:57 dillon Exp $ */ #include "opt_ktrace.h" #include #include #include #include #include #include #include #include #ifdef KTRACE #include #include #endif #include #include #include #include static void sched_setup __P((void *dummy)); SYSINIT(sched_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, sched_setup, NULL) u_char curpriority; int hogticks; int lbolt; int sched_quantum; /* Roundrobin scheduling quantum in ticks. */ static struct callout loadav_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 int curpriority_cmp __P((struct proc *p)); static void endtsleep __P((void *)); static void loadav __P((void *arg)); static void maybe_resched __P((struct proc *chk)); static void roundrobin __P((void *arg)); static void schedcpu __P((void *arg)); static void updatepri __P((struct proc *p)); 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", ""); /*- * Compare priorities. Return: * <0: priority of p < current priority * 0: priority of p == current priority * >0: priority of p > current priority * The priorities are the normal priorities or the normal realtime priorities * if p is on the same scheduler as curproc. Otherwise the process on the * more realtimeish scheduler has lowest priority. As usual, a higher * priority really means a lower priority. */ static int curpriority_cmp(p) struct proc *p; { int c_class, p_class; c_class = RTP_PRIO_BASE(curproc->p_rtprio.type); p_class = RTP_PRIO_BASE(p->p_rtprio.type); if (p_class != c_class) return (p_class - c_class); if (p_class == RTP_PRIO_NORMAL) return (((int)p->p_priority - (int)curpriority) / PPQ); return ((int)p->p_rtprio.prio - (int)curproc->p_rtprio.prio); } /* * Arrange to reschedule if necessary, taking the priorities and * schedulers into account. */ static void maybe_resched(chk) struct proc *chk; { struct proc *p = curproc; /* XXX */ /* * XXX idle scheduler still broken because proccess stays on idle * scheduler during waits (such as when getting FS locks). If a * standard process becomes runaway cpu-bound, the system can lockup * due to idle-scheduler processes in wakeup never getting any cpu. */ if (p == NULL) { #if 0 need_resched(); #endif } else if (chk == p) { /* We may need to yield if our priority has been raised. */ if (curpriority_cmp(chk) > 0) need_resched(); } else if (curpriority_cmp(chk) < 0) need_resched(); } int roundrobin_interval(void) { return (sched_quantum); } /* * Force switch among equal priority processes every 100ms. */ /* ARGSUSED */ static void roundrobin(arg) void *arg; { #ifndef SMP struct proc *p = curproc; /* XXX */ #endif #ifdef SMP need_resched(); forward_roundrobin(); #else if (p == 0 || RTP_PRIO_NEED_RR(p->p_rtprio.type)) need_resched(); #endif timeout(roundrobin, NULL, sched_quantum); } /* * 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. */ /* ARGSUSED */ static void schedcpu(arg) void *arg; { register fixpt_t loadfac = loadfactor(averunnable.ldavg[0]); register struct proc *p; register int realstathz, s; realstathz = stathz ? stathz : hz; LIST_FOREACH(p, &allproc, p_list) { /* * 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. */ p->p_swtime++; if (p->p_stat == SSLEEP || p->p_stat == SSTOP) p->p_slptime++; p->p_pctcpu = (p->p_pctcpu * ccpu) >> FSHIFT; /* * If the process has slept the entire second, * stop recalculating its priority until it wakes up. */ if (p->p_slptime > 1) continue; s = splhigh(); /* prevent state changes and protect run queue */ /* * p_pctcpu is only for ps. */ #if (FSHIFT >= CCPU_SHIFT) p->p_pctcpu += (realstathz == 100)? ((fixpt_t) p->p_cpticks) << (FSHIFT - CCPU_SHIFT): 100 * (((fixpt_t) p->p_cpticks) << (FSHIFT - CCPU_SHIFT)) / realstathz; #else p->p_pctcpu += ((FSCALE - ccpu) * (p->p_cpticks * FSCALE / realstathz)) >> FSHIFT; #endif p->p_cpticks = 0; p->p_estcpu = decay_cpu(loadfac, p->p_estcpu); resetpriority(p); if (p->p_priority >= PUSER) { if ((p != curproc) && #ifdef SMP p->p_oncpu == 0xff && /* idle */ #endif p->p_stat == SRUN && (p->p_flag & P_INMEM) && (p->p_priority / PPQ) != (p->p_usrpri / PPQ)) { remrunqueue(p); p->p_priority = p->p_usrpri; setrunqueue(p); } else { p->p_priority = p->p_usrpri; } } splx(s); } wakeup((caddr_t)&lbolt); timeout(schedcpu, (void *)0, hz); } /* * 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. */ static void updatepri(p) register struct proc *p; { register unsigned int newcpu = p->p_estcpu; register fixpt_t loadfac = loadfactor(averunnable.ldavg[0]); if (p->p_slptime > 5 * loadfac) p->p_estcpu = 0; else { p->p_slptime--; /* the first time was done in schedcpu */ while (newcpu && --p->p_slptime) newcpu = decay_cpu(loadfac, newcpu); p->p_estcpu = newcpu; } resetpriority(p); } /* * 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, proc) slpque[TABLESIZE]; #define LOOKUP(x) (((intptr_t)(x) >> 8) & (TABLESIZE - 1)) /* * During autoconfiguration or after a panic, a sleep will simply * lower the priority briefly to allow interrupts, then return. * The priority to be used (safepri) is machine-dependent, thus this * value is initialized and maintained in the machine-dependent layers. * This priority will typically be 0, or the lowest priority * that is safe for use on the interrupt stack; it can be made * higher to block network software interrupts after panics. */ int safepri; 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). */ int tsleep(ident, priority, wmesg, timo) void *ident; int priority, timo; const char *wmesg; { struct thread *td = curthread; struct proc *p = td->td_proc; int s, sig, catch = priority & PCATCH; int id = LOOKUP(ident); struct callout_handle thandle; #ifdef KTRACE if (KTRPOINT(td, KTR_CSW)) ktrcsw(p->p_tracep, 1, 0); #endif s = splhigh(); 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. */ splx(safepri); splx(s); return (0); } KASSERT(p != NULL, ("tsleep1")); KASSERT(ident != NULL && p->p_stat == SRUN, ("tsleep %p %s %d", ident, wmesg, p->p_stat)); p->p_wchan = ident; p->p_wmesg = wmesg; p->p_slptime = 0; p->p_priority = priority & PRIMASK; TAILQ_INSERT_TAIL(&slpque[id], p, p_procq); if (timo) thandle = timeout(endtsleep, (void *)p, timo); /* * 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, p->p_wchan will be 0 upon return from CURSIG. */ if (catch) { p->p_flag |= P_SINTR; if ((sig = CURSIG(p))) { if (p->p_wchan) unsleep(p); p->p_stat = SRUN; goto resume; } if (p->p_wchan == 0) { catch = 0; goto resume; } } else sig = 0; p->p_stat = SSLEEP; p->p_stats->p_ru.ru_nvcsw++; mi_switch(); resume: curpriority = p->p_usrpri; splx(s); p->p_flag &= ~P_SINTR; if (p->p_flag & P_TIMEOUT) { p->p_flag &= ~P_TIMEOUT; if (sig == 0) { #ifdef KTRACE if (KTRPOINT(td, KTR_CSW)) ktrcsw(p->p_tracep, 0, 0); #endif return (EWOULDBLOCK); } } else if (timo) untimeout(endtsleep, (void *)p, thandle); if (catch && (sig != 0 || (sig = CURSIG(p)))) { #ifdef KTRACE if (KTRPOINT(td, KTR_CSW)) ktrcsw(p->p_tracep, 0, 0); #endif if (SIGISMEMBER(p->p_sigacts->ps_sigintr, sig)) return (EINTR); return (ERESTART); } #ifdef KTRACE if (KTRPOINT(td, KTR_CSW)) ktrcsw(p->p_tracep, 0, 0); #endif return (0); } /* * General sleep call. Suspends the current process until a wakeup is * performed on the specified xwait structure. 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). * * If the passed generation number is different from the generation number * in the xwait, return immediately. */ int xsleep(struct xwait *w, int priority, const char *wmesg, int timo, int *gen) { struct thread *td = curthread; struct proc *p = td->td_proc; int s, sig, catch = priority & PCATCH; struct callout_handle thandle; #ifdef KTRACE if (KTRPOINT(td, KTR_CSW)) ktrcsw(p->p_tracep, 1, 0); #endif s = splhigh(); 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. */ splx(safepri); splx(s); return (0); } KASSERT(p != NULL, ("xsleep1")); KASSERT(w != NULL && p->p_stat == SRUN, ("xsleep")); /* * If the generation number does not match we return immediately. */ if (*gen != w->gen) { *gen = w->gen; splx(s); #ifdef KTRACE if (KTRPOINT(td, KTR_CSW)) ktrcsw(p->p_tracep, 0, 0); #endif return(0); } p->p_wchan = w; p->p_wmesg = wmesg; p->p_slptime = 0; p->p_priority = priority & PRIMASK; p->p_flag |= P_XSLEEP; TAILQ_INSERT_TAIL(&w->waitq, p, p_procq); if (timo) thandle = timeout(endtsleep, (void *)p, timo); /* * 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, p->p_wchan will be 0 upon return from CURSIG. */ if (catch) { p->p_flag |= P_SINTR; if ((sig = CURSIG(p))) { if (p->p_wchan) unsleep(p); p->p_stat = SRUN; goto resume; } if (p->p_wchan == NULL) { catch = 0; goto resume; } } else sig = 0; p->p_stat = SSLEEP; p->p_stats->p_ru.ru_nvcsw++; mi_switch(); resume: curpriority = p->p_usrpri; *gen = w->gen; /* update generation number */ splx(s); p->p_flag &= ~P_SINTR; if (p->p_flag & P_TIMEOUT) { p->p_flag &= ~P_TIMEOUT; if (sig == 0) { #ifdef KTRACE if (KTRPOINT(td, KTR_CSW)) ktrcsw(p->p_tracep, 0, 0); #endif return (EWOULDBLOCK); } } else if (timo) untimeout(endtsleep, (void *)p, thandle); if (catch && (sig != 0 || (sig = CURSIG(p)))) { #ifdef KTRACE if (KTRPOINT(td, KTR_CSW)) ktrcsw(p->p_tracep, 0, 0); #endif if (SIGISMEMBER(p->p_sigacts->ps_sigintr, sig)) return (EINTR); return (ERESTART); } #ifdef KTRACE if (KTRPOINT(td, KTR_CSW)) ktrcsw(p->p_tracep, 0, 0); #endif return (0); } /* * Implement timeout for tsleep or xsleep * * 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. */ static void endtsleep(arg) void *arg; { register struct proc *p; int s; p = (struct proc *)arg; s = splhigh(); if (p->p_wchan) { if (p->p_stat == SSLEEP) setrunnable(p); else unsleep(p); p->p_flag |= P_TIMEOUT; } splx(s); } /* * Remove a process from its wait queue */ void unsleep(p) register struct proc *p; { int s; s = splhigh(); if (p->p_wchan) { if (p->p_flag & P_XSLEEP) { struct xwait *w = p->p_wchan; TAILQ_REMOVE(&w->waitq, p, p_procq); p->p_flag &= ~P_XSLEEP; } else { TAILQ_REMOVE(&slpque[LOOKUP(p->p_wchan)], p, p_procq); } p->p_wchan = NULL; } splx(s); } /* * Make all processes sleeping on the explicit lock structure runnable. */ void xwakeup(struct xwait *w) { struct proc *p; int s; s = splhigh(); ++w->gen; while ((p = TAILQ_FIRST(&w->waitq)) != NULL) { TAILQ_REMOVE(&w->waitq, p, p_procq); KASSERT(p->p_wchan == w && (p->p_flag & P_XSLEEP), ("xwakeup: wchan mismatch for %p (%p/%p) %08x", p, p->p_wchan, w, p->p_flag & P_XSLEEP)); p->p_wchan = NULL; p->p_flag &= ~P_XSLEEP; if (p->p_stat == SSLEEP) { /* OPTIMIZED EXPANSION OF setrunnable(p); */ if (p->p_slptime > 1) updatepri(p); p->p_slptime = 0; p->p_stat = SRUN; if (p->p_flag & P_INMEM) { setrunqueue(p); maybe_resched(p); } else { p->p_flag |= P_SWAPINREQ; wakeup((caddr_t)&proc0); } } } splx(s); } /* * Make all processes sleeping on the specified identifier runnable. */ void wakeup(ident) register void *ident; { register struct slpquehead *qp; register struct proc *p; struct proc *np; int s; int id = LOOKUP(ident); s = splhigh(); qp = &slpque[id]; restart: for (p = TAILQ_FIRST(qp); p != NULL; p = np) { np = TAILQ_NEXT(p, p_procq); if (p->p_wchan == ident) { TAILQ_REMOVE(qp, p, p_procq); p->p_wchan = NULL; if (p->p_stat == SSLEEP) { /* OPTIMIZED EXPANSION OF setrunnable(p); */ if (p->p_slptime > 1) updatepri(p); p->p_slptime = 0; p->p_stat = SRUN; if (p->p_flag & P_INMEM) { setrunqueue(p); maybe_resched(p); } else { p->p_flag |= P_SWAPINREQ; wakeup((caddr_t)&proc0); } /* END INLINE EXPANSION */ goto restart; } } } splx(s); } /* * 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 proc *p; struct proc *np; int s; int id = LOOKUP(ident); s = splhigh(); qp = &slpque[id]; restart: for (p = TAILQ_FIRST(qp); p != NULL; p = np) { np = TAILQ_NEXT(p, p_procq); if (p->p_wchan == ident) { TAILQ_REMOVE(qp, p, p_procq); p->p_wchan = 0; if (p->p_stat == SSLEEP) { /* OPTIMIZED EXPANSION OF setrunnable(p); */ if (p->p_slptime > 1) updatepri(p); p->p_slptime = 0; p->p_stat = SRUN; if (p->p_flag & P_INMEM) { setrunqueue(p); maybe_resched(p); break; } else { p->p_flag |= P_SWAPINREQ; wakeup((caddr_t)&proc0); } /* END INLINE EXPANSION */ goto restart; } } } splx(s); } /* * The machine independent parts of mi_switch(). * Must be called at splstatclock() or higher. */ void mi_switch() { struct thread *td = curthread; struct proc *p = td->td_proc; /* XXX */ struct rlimit *rlim; int x; u_int64_t ttime; /* * XXX this spl is almost unnecessary. It is partly to allow for * sloppy callers that don't do it (issignal() via CURSIG() is the * main offender). It is partly to work around a bug in the i386 * cpu_switch() (the ipl is not preserved). We ran for years * without it. I think there was only a interrupt latency problem. * The main caller, tsleep(), does an splx() a couple of instructions * after calling here. The buggy caller, issignal(), usually calls * here at spl0() and sometimes returns at splhigh(). The process * then runs for a little too long at splhigh(). The ipl gets fixed * when the process returns to user mode (or earlier). * * It would probably be better to always call here at spl0(). Callers * are prepared to give up control to another process, so they must * be prepared to be interrupted. The clock stuff here may not * actually need splstatclock(). */ x = splstatclock(); clear_resched(); #ifdef SIMPLELOCK_DEBUG if (p->p_simple_locks) printf("sleep: holding simple lock\n"); #endif /* * Check if the process exceeds its cpu resource allocation. * If over max, kill it. Time spent in interrupts is not * included. YYY 64 bit match is expensive. Ick. */ ttime = td->td_sticks + td->td_uticks; if (p->p_stat != SZOMB && p->p_limit->p_cpulimit != RLIM_INFINITY && ttime > p->p_limit->p_cpulimit) { rlim = &p->p_rlimit[RLIMIT_CPU]; if (ttime / (rlim_t)1000000 >= rlim->rlim_max) { killproc(p, "exceeded maximum CPU limit"); } else { psignal(p, SIGXCPU); if (rlim->rlim_cur < rlim->rlim_max) { /* XXX: we should make a private copy */ rlim->rlim_cur += 5; } } } /* * Pick a new current process and record its start time. * YYY lwkt_switch() will run the heavy weight process restoration * code, which removes the target thread and process from their * respective run queues to temporarily mimic 5.x behavior. * YYY the userland scheduler should pick only one user process * at a time to run per cpu. */ cnt.v_swtch++; lwkt_switch(); remrunqueue(p); splx(x); } /* * 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(p) register struct proc *p; { register int s; s = splhigh(); switch (p->p_stat) { case 0: case SRUN: case SZOMB: default: panic("setrunnable"); case SSTOP: case SSLEEP: unsleep(p); /* e.g. when sending signals */ break; case SIDL: break; } p->p_stat = SRUN; if (p->p_flag & P_INMEM) setrunqueue(p); splx(s); if (p->p_slptime > 1) updatepri(p); p->p_slptime = 0; if ((p->p_flag & P_INMEM) == 0) { p->p_flag |= P_SWAPINREQ; wakeup((caddr_t)&proc0); } else maybe_resched(p); } /* * 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(p) register struct proc *p; { register unsigned int newpriority; if (p->p_rtprio.type == RTP_PRIO_NORMAL) { newpriority = PUSER + p->p_estcpu / INVERSE_ESTCPU_WEIGHT + NICE_WEIGHT * p->p_nice; newpriority = min(newpriority, MAXPRI); p->p_usrpri = newpriority; } maybe_resched(p); } /* * Compute a tenex style load average of a quantity on * 1, 5 and 15 minute intervals. */ static void loadav(void *arg) { int i, nrun; struct loadavg *avg; struct proc *p; avg = &averunnable; nrun = 0; LIST_FOREACH(p, &allproc, p_list) { switch (p->p_stat) { case SRUN: case SIDL: nrun++; } } 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(&loadav_callout); /* 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(p) struct proc *p; { p->p_cpticks++; p->p_estcpu = ESTCPULIM(p->p_estcpu + 1); if ((p->p_estcpu % INVERSE_ESTCPU_WEIGHT) == 0) { resetpriority(p); if (p->p_priority >= PUSER) p->p_priority = p->p_usrpri; } }