/*- * 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 * $Id: kern_synch.c,v 1.49 1998/03/08 09:56:59 julian Exp $ */ #include "opt_ktrace.h" #include #include #include #include #include #include #include #include #include #include #ifdef KTRACE #include #endif #include #include /* for UCHAR_MAX = typeof(p_priority)_MAX */ static void rqinit __P((void *)); SYSINIT(runqueue, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, rqinit, NULL) u_char curpriority; /* usrpri of curproc */ int lbolt; /* once a second sleep address */ static void endtsleep __P((void *)); static void roundrobin __P((void *arg)); static void schedcpu __P((void *arg)); static void updatepri __P((struct proc *p)); #define MAXIMUM_SCHEDULE_QUANTUM (1000000) /* arbitrary limit */ #ifndef DEFAULT_SCHEDULE_QUANTUM #define DEFAULT_SCHEDULE_QUANTUM 10 #endif static int quantum = DEFAULT_SCHEDULE_QUANTUM; /* default value */ static int sysctl_kern_quantum SYSCTL_HANDLER_ARGS { int error; int new_val = quantum; new_val = quantum; error = sysctl_handle_int(oidp, &new_val, 0, req); if (error == 0) { if ((new_val > 0) && (new_val < MAXIMUM_SCHEDULE_QUANTUM)) { quantum = new_val; } else { error = EINVAL; } } return (error); } SYSCTL_PROC(_kern, OID_AUTO, quantum, CTLTYPE_INT|CTLFLAG_RW, 0, sizeof quantum, sysctl_kern_quantum, "I", ""); /* maybe_resched: Decide if you need to reschedule or not * taking the priorities and schedulers into account. */ static void maybe_resched(struct proc *chk) { struct proc *p = curproc; /* XXX */ /* If the current scheduler is the idle scheduler or * the priority of the new one is higher then reschedule. */ if (p == 0 || RTP_PRIO_BASE(p->p_rtprio.type) == RTP_PRIO_IDLE || (chk->p_priority < curpriority && RTP_PRIO_BASE(p->p_rtprio.type) == RTP_PRIO_BASE(chk->p_rtprio.type)) ) need_resched(); } #define ROUNDROBIN_INTERVAL (hz / quantum) int roundrobin_interval(void) { return ROUNDROBIN_INTERVAL; } /* * Force switch among equal priority processes every 100ms. */ /* ARGSUSED */ static void roundrobin(arg) void *arg; { struct proc *p = curproc; /* XXX */ if (p == 0 || RTP_PRIO_NEED_RR(p->p_rtprio.type)) need_resched(); timeout(roundrobin, NULL, ROUNDROBIN_INTERVAL); } /* * 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 statclock() 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) */ /* * 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 s; register unsigned int newcpu; for (p = allproc.lh_first; p != 0; p = p->p_list.le_next) { /* * 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 += (hz == 100)? ((fixpt_t) p->p_cpticks) << (FSHIFT - CCPU_SHIFT): 100 * (((fixpt_t) p->p_cpticks) << (FSHIFT - CCPU_SHIFT)) / hz; #else p->p_pctcpu += ((FSCALE - ccpu) * (p->p_cpticks * FSCALE / hz)) >> FSHIFT; #endif p->p_cpticks = 0; newcpu = (u_int) decay_cpu(loadfac, p->p_estcpu) + p->p_nice; p->p_estcpu = min(newcpu, UCHAR_MAX); resetpriority(p); if (p->p_priority >= PUSER) { #define PPQ (128 / NQS) /* priorities per queue */ if ((p != curproc) && #ifdef SMP (u_char)p->p_oncpu == 0xff && /* idle */ #endif p->p_stat == SRUN && (p->p_flag & P_INMEM) && (p->p_priority / PPQ) != (p->p_usrpri / PPQ)) { remrq(p); p->p_priority = p->p_usrpri; setrunqueue(p); } else p->p_priority = p->p_usrpri; } splx(s); } vmmeter(); 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 = (int) decay_cpu(loadfac, newcpu); p->p_estcpu = min(newcpu, UCHAR_MAX); } 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) (((long)(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() { int i; 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 proc *p = curproc; int s, sig, catch = priority & PCATCH; struct callout_handle thandle; #ifdef KTRACE if (KTRPOINT(p, 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); } #ifdef DIAGNOSTIC if(p == NULL) panic("tsleep1"); if (ident == NULL || p->p_stat != SRUN) panic("tsleep"); /* XXX This is not exhaustive, just the most common case */ if ((p->p_procq.tqe_prev != NULL) && (*p->p_procq.tqe_prev == p)) panic("sleeping process already on another queue"); #endif p->p_wchan = ident; p->p_wmesg = wmesg; p->p_slptime = 0; p->p_priority = priority & PRIMASK; TAILQ_INSERT_TAIL(&slpque[LOOKUP(ident)], 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(p, 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(p, KTR_CSW)) ktrcsw(p->p_tracep, 0, 0); #endif if (p->p_sigacts->ps_sigintr & sigmask(sig)) return (EINTR); return (ERESTART); } #ifdef KTRACE if (KTRPOINT(p, KTR_CSW)) ktrcsw(p->p_tracep, 0, 0); #endif return (0); } /* * Implement timeout for tsleep. * 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) { TAILQ_REMOVE(&slpque[LOOKUP(p->p_wchan)], p, p_procq); p->p_wchan = 0; } 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; int s; s = splhigh(); qp = &slpque[LOOKUP(ident)]; restart: for (p = qp->tqh_first; p != NULL; p = p->p_procq.tqe_next) { #ifdef DIAGNOSTIC if (p->p_stat != SSLEEP && p->p_stat != SSTOP) panic("wakeup"); #endif 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); } 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 prcoess is currently * swapped out. */ void wakeup_one(ident) register void *ident; { register struct slpquehead *qp; register struct proc *p; int s; s = splhigh(); qp = &slpque[LOOKUP(ident)]; for (p = qp->tqh_first; p != NULL; p = p->p_procq.tqe_next) { #ifdef DIAGNOSTIC if (p->p_stat != SSLEEP && p->p_stat != SSTOP) panic("wakeup_one"); #endif 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 */ } } } splx(s); } /* * The machine independent parts of mi_switch(). * Must be called at splstatclock() or higher. */ void mi_switch() { register struct proc *p = curproc; /* XXX */ register struct rlimit *rlim; register long s, u; int x; struct timeval tv; /* * 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(); #ifdef SIMPLELOCK_DEBUG if (p->p_simple_locks) printf("sleep: holding simple lock\n"); #endif /* * Compute the amount of time during which the current * process was running, and add that to its total so far. */ microtime(&tv); u = p->p_rtime.tv_usec + (tv.tv_usec - runtime.tv_usec); s = p->p_rtime.tv_sec + (tv.tv_sec - runtime.tv_sec); if (u < 0) { u += 1000000; s--; } else if (u >= 1000000) { u -= 1000000; s++; } #ifdef SMP if (s < 0) s = u = 0; #endif p->p_rtime.tv_usec = u; p->p_rtime.tv_sec = s; /* * Check if the process exceeds its cpu resource allocation. * If over max, kill it. */ if (p->p_stat != SZOMB) { rlim = &p->p_rlimit[RLIMIT_CPU]; if (s >= rlim->rlim_cur) { if (s >= rlim->rlim_max) killproc(p, "exceeded maximum CPU limit"); else { psignal(p, SIGXCPU); if (rlim->rlim_cur < rlim->rlim_max) rlim->rlim_cur += 5; } } } /* * Pick a new current process and record its start time. */ cnt.v_swtch++; cpu_switch(p); microtime(&runtime); splx(x); } /* * Initialize the (doubly-linked) run queues * to be empty. */ /* ARGSUSED*/ static void rqinit(dummy) void *dummy; { register int i; for (i = 0; i < NQS; i++) { qs[i].ph_link = qs[i].ph_rlink = (struct proc *)&qs[i]; rtqs[i].ph_link = rtqs[i].ph_rlink = (struct proc *)&rtqs[i]; idqs[i].ph_link = idqs[i].ph_rlink = (struct proc *)&idqs[i]; } } /* * 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 / 4 + 2 * p->p_nice; newpriority = min(newpriority, MAXPRI); p->p_usrpri = newpriority; } maybe_resched(p); } /* ARGSUSED */ static void sched_setup __P((void *dummy)); static void sched_setup(dummy) void *dummy; { /* Kick off timeout driven events by calling first time. */ roundrobin(NULL); schedcpu(NULL); } SYSINIT(sched_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, sched_setup, NULL)