/*- * Copyright (c) 1982, 1986, 1990 The Regents of the University of California. * Copyright (c) 1991 The Regents of the University of California. * 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. * 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 7.18 (Berkeley) 6/27/91 */ #include "param.h" #include "systm.h" #include "proc.h" #include "kernel.h" #include "buf.h" #include "signalvar.h" #include "resourcevar.h" #include "machine/cpu.h" u_char curpri; /* usrpri of curproc */ /* * Force switch among equal priority processes every 100ms. */ roundrobin() { need_resched(); timeout(roundrobin, (caddr_t)0, hz / 10); } /* * constants for digital decay and forget * 90% of (p_cpu) 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 hardclock updates p_cpu and p_cpticks independently. * * We wish to decay away 90% of p_cpu 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_cpu *= decay; * will compute * p_cpu *= 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 */ 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 dont 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, once a second */ schedcpu() { register fixpt_t loadfac = loadfactor(averunnable[0]); register struct proc *p; register int s; register unsigned int newcpu; wakeup((caddr_t)&lbolt); for (p = allproc; p != NULL; p = p->p_nxt) { /* * 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_time++; 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; /* * 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_cpu) + p->p_nice; p->p_cpu = min(newcpu, UCHAR_MAX); setpri(p); s = splhigh(); /* prevent state changes */ if (p->p_pri >= PUSER) { #define PPQ (128 / NQS) /* priorities per queue */ if ((p != curproc) && p->p_stat == SRUN && (p->p_flag & SLOAD) && (p->p_pri / PPQ) != (p->p_usrpri / PPQ)) { remrq(p); p->p_pri = p->p_usrpri; setrq(p); } else p->p_pri = p->p_usrpri; } splx(s); } vmmeter(); if (bclnlist != NULL) wakeup((caddr_t)pageproc); timeout(schedcpu, (caddr_t)0, hz); } /* * Recalculate the priority of a process after it has slept for a while. * For all load averages >= 1 and max p_cpu of 255, sleeping for at least * six times the loadfactor will decay p_cpu to zero. */ updatepri(p) register struct proc *p; { register unsigned int newcpu = p->p_cpu; register fixpt_t loadfac = loadfactor(averunnable[0]); if (p->p_slptime > 5 * loadfac) p->p_cpu = 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_cpu = min(newcpu, UCHAR_MAX); } setpri(p); } #define SQSIZE 0100 /* Must be power of 2 */ #define HASH(x) (( (int) x >> 5) & (SQSIZE-1)) struct slpque { struct proc *sq_head; struct proc **sq_tailp; } slpque[SQSIZE]; /* * 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; /* * General sleep call. * Suspends current process until a wakeup is made on chan. * The process will then be made runnable with priority pri. * 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). */ tsleep(chan, pri, wmesg, timo) caddr_t chan; int pri; char *wmesg; int timo; { register struct proc *p = curproc; register struct slpque *qp; register s; int sig, catch = pri & PCATCH; extern int cold; int endtsleep(); 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 (chan == 0 || p->p_stat != SRUN || p->p_rlink) panic("tsleep"); #endif p->p_wchan = chan; p->p_wmesg = wmesg; p->p_slptime = 0; p->p_pri = pri & PRIMASK; qp = &slpque[HASH(chan)]; if (qp->sq_head == 0) qp->sq_head = p; else *qp->sq_tailp = p; *(qp->sq_tailp = &p->p_link) = 0; if (timo) timeout(endtsleep, (caddr_t)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 |= SSINTR; 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; } } p->p_stat = SSLEEP; p->p_stats->p_ru.ru_nvcsw++; swtch(); resume: curpri = p->p_usrpri; splx(s); p->p_flag &= ~SSINTR; if (p->p_flag & STIMO) { p->p_flag &= ~STIMO; if (catch == 0 || sig == 0) return (EWOULDBLOCK); } else if (timo) untimeout(endtsleep, (caddr_t)p); if (catch && (sig != 0 || (sig = CURSIG(p)))) { if (p->p_sigacts->ps_sigintr & sigmask(sig)) return (EINTR); return (ERESTART); } 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. */ endtsleep(p) register struct proc *p; { int s = splhigh(); if (p->p_wchan) { if (p->p_stat == SSLEEP) setrun(p); else unsleep(p); p->p_flag |= STIMO; } splx(s); } /* * Short-term, non-interruptable sleep. */ sleep(chan, pri) caddr_t chan; int pri; { register struct proc *p = curproc; register struct slpque *qp; register s; extern int cold; #ifdef DIAGNOSTIC if (pri > PZERO) { printf("sleep called with pri %d > PZERO, wchan: %x\n", pri, chan); panic("old sleep"); } #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; } #ifdef DIAGNOSTIC if (chan==0 || p->p_stat != SRUN || p->p_rlink) panic("sleep"); #endif p->p_wchan = chan; p->p_wmesg = NULL; p->p_slptime = 0; p->p_pri = pri; qp = &slpque[HASH(chan)]; if (qp->sq_head == 0) qp->sq_head = p; else *qp->sq_tailp = p; *(qp->sq_tailp = &p->p_link) = 0; p->p_stat = SSLEEP; p->p_stats->p_ru.ru_nvcsw++; swtch(); curpri = p->p_usrpri; splx(s); } /* * Remove a process from its wait queue */ unsleep(p) register struct proc *p; { register struct slpque *qp; register struct proc **hp; int s; s = splhigh(); if (p->p_wchan) { hp = &(qp = &slpque[HASH(p->p_wchan)])->sq_head; while (*hp != p) hp = &(*hp)->p_link; *hp = p->p_link; if (qp->sq_tailp == &p->p_link) qp->sq_tailp = hp; p->p_wchan = 0; } splx(s); } /* * Wakeup on "chan"; set all processes * sleeping on chan to run state. */ wakeup(chan) register caddr_t chan; { register struct slpque *qp; register struct proc *p, **q; int s; s = splhigh(); qp = &slpque[HASH(chan)]; restart: for (q = &qp->sq_head; p = *q; ) { #ifdef DIAGNOSTIC if (p->p_rlink || p->p_stat != SSLEEP && p->p_stat != SSTOP) panic("wakeup"); #endif if (p->p_wchan == chan) { p->p_wchan = 0; *q = p->p_link; if (qp->sq_tailp == &p->p_link) qp->sq_tailp = q; if (p->p_stat == SSLEEP) { /* OPTIMIZED INLINE EXPANSION OF setrun(p) */ if (p->p_slptime > 1) updatepri(p); p->p_slptime = 0; p->p_stat = SRUN; if (p->p_flag & SLOAD) setrq(p); /* * Since curpri is a usrpri, * p->p_pri is always better than curpri. */ if ((p->p_flag&SLOAD) == 0) wakeup((caddr_t)&proc0); else need_resched(); /* END INLINE EXPANSION */ goto restart; } } else q = &p->p_link; } splx(s); } /* * Initialize the (doubly-linked) run queues * to be empty. */ rqinit() { register int i; for (i = 0; i < NQS; i++) qs[i].ph_link = qs[i].ph_rlink = (struct proc *)&qs[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. */ setrun(p) register struct proc *p; { register int s; s = splhigh(); switch (p->p_stat) { case 0: case SWAIT: case SRUN: case SZOMB: default: panic("setrun"); case SSTOP: case SSLEEP: unsleep(p); /* e.g. when sending signals */ break; case SIDL: break; } p->p_stat = SRUN; if (p->p_flag & SLOAD) setrq(p); splx(s); if (p->p_slptime > 1) updatepri(p); p->p_slptime = 0; if ((p->p_flag&SLOAD) == 0) wakeup((caddr_t)&proc0); else if (p->p_pri < curpri) need_resched(); } /* * Compute priority of process when running in user mode. * Arrange to reschedule if the resulting priority * is better than that of the current process. */ setpri(p) register struct proc *p; { register unsigned int newpri; newpri = PUSER + p->p_cpu / 4 + 2 * p->p_nice; newpri = min(newpri, MAXPRI); p->p_usrpri = newpri; if (newpri < curpri) need_resched(); }