Return to kern_synch.c CVS log

Up to [CSRG BSD Unix] / 43BSDReno / sys / kern

Annotation of 43BSDReno/sys/kern/kern_synch.c, revision 1.1

1.1     ! root        1: /*
        !             2:  * Copyright (c) 1982, 1986, 1990 Regents of the University of California.
        !             3:  * All rights reserved.  The Berkeley software License Agreement
        !             4:  * specifies the terms and conditions for redistribution.
        !             5:  *
        !             6:  *     @(#)kern_synch.c        7.11 (Berkeley) 4/3/90
        !             7:  */
        !             8: 
        !             9: #include "machine/pte.h"
        !            10: #include "machine/psl.h"
        !            11: #include "machine/mtpr.h"
        !            12: 
        !            13: #include "param.h"
        !            14: #include "systm.h"
        !            15: #include "user.h"
        !            16: #include "proc.h"
        !            17: #include "vm.h"
        !            18: #include "kernel.h"
        !            19: #include "buf.h"
        !            20: 
        !            21: /*
        !            22:  * Force switch among equal priority processes every 100ms.
        !            23:  */
        !            24: roundrobin()
        !            25: {
        !            26: 
        !            27:        runrun++;
        !            28:        aston();
        !            29:        timeout(roundrobin, (caddr_t)0, hz / 10);
        !            30: }
        !            31: 
        !            32: /*
        !            33:  * constants for digital decay and forget
        !            34:  *     90% of (p_cpu) usage in 5*loadav time
        !            35:  *     95% of (p_pctcpu) usage in 60 seconds (load insensitive)
        !            36:  *          Note that, as ps(1) mentions, this can let percentages
        !            37:  *          total over 100% (I've seen 137.9% for 3 processes).
        !            38:  *
        !            39:  * Note that hardclock updates p_cpu and p_cpticks independently.
        !            40:  *
        !            41:  * We wish to decay away 90% of p_cpu in (5 * loadavg) seconds.
        !            42:  * That is, the system wants to compute a value of decay such
        !            43:  * that the following for loop:
        !            44:  *     for (i = 0; i < (5 * loadavg); i++)
        !            45:  *             p_cpu *= decay;
        !            46:  * will compute
        !            47:  *     p_cpu *= 0.1;
        !            48:  * for all values of loadavg:
        !            49:  *
        !            50:  * Mathematically this loop can be expressed by saying:
        !            51:  *     decay ** (5 * loadavg) ~= .1
        !            52:  *
        !            53:  * The system computes decay as:
        !            54:  *     decay = (2 * loadavg) / (2 * loadavg + 1)
        !            55:  *
        !            56:  * We wish to prove that the system's computation of decay
        !            57:  * will always fulfill the equation:
        !            58:  *     decay ** (5 * loadavg) ~= .1
        !            59:  *
        !            60:  * If we compute b as:
        !            61:  *     b = 2 * loadavg
        !            62:  * then
        !            63:  *     decay = b / (b + 1)
        !            64:  *
        !            65:  * We now need to prove two things:
        !            66:  *     1) Given factor ** (5 * loadavg) ~= .1, prove factor == b/(b+1)
        !            67:  *     2) Given b/(b+1) ** power ~= .1, prove power == (5 * loadavg)
        !            68:  *     
        !            69:  * Facts:
        !            70:  *         For x close to zero, exp(x) =~ 1 + x, since
        !            71:  *              exp(x) = 0! + x**1/1! + x**2/2! + ... .
        !            72:  *              therefore exp(-1/b) =~ 1 - (1/b) = (b-1)/b.
        !            73:  *         For x close to zero, ln(1+x) =~ x, since
        !            74:  *              ln(1+x) = x - x**2/2 + x**3/3 - ...     -1 < x < 1
        !            75:  *              therefore ln(b/(b+1)) = ln(1 - 1/(b+1)) =~ -1/(b+1).
        !            76:  *         ln(.1) =~ -2.30
        !            77:  *
        !            78:  * Proof of (1):
        !            79:  *    Solve (factor)**(power) =~ .1 given power (5*loadav):
        !            80:  *     solving for factor,
        !            81:  *      ln(factor) =~ (-2.30/5*loadav), or
        !            82:  *      factor =~ exp(-1/((5/2.30)*loadav) =~ exp(-1/(2*loadav)) =
        !            83:  *          exp(-1/b) =~ (b-1)/b =~ b/(b+1).                    QED
        !            84:  *
        !            85:  * Proof of (2):
        !            86:  *    Solve (factor)**(power) =~ .1 given factor == (b/(b+1)):
        !            87:  *     solving for power,
        !            88:  *      power*ln(b/(b+1)) =~ -2.30, or
        !            89:  *      power =~ 2.3 * (b + 1) = 4.6*loadav + 2.3 =~ 5*loadav.  QED
        !            90:  *
        !            91:  * Actual power values for the implemented algorithm are as follows:
        !            92:  *      loadav: 1       2       3       4
        !            93:  *      power:  5.68    10.32   14.94   19.55
        !            94:  */
        !            95: 
        !            96: /* calculations for digital decay to forget 90% of usage in 5*loadav sec */
        !            97: #define        get_b(loadav)           (2 * (loadav))
        !            98: #define        get_pcpu(b, cpu)        (((b) * ((cpu) & 0377)) / ((b) + FSCALE))
        !            99: 
        !           100: /* decay 95% of `p_pctcpu' in 60 seconds; see CCPU_SHIFT before changing */
        !           101: fixpt_t        ccpu = 0.95122942450071400909 * FSCALE;         /* exp(-1/20) */
        !           102: 
        !           103: /*
        !           104:  * If `ccpu' is not equal to `exp(-1/20)' and you still want to use the
        !           105:  * faster/more-accurate formula, you'll have to estimate CCPU_SHIFT below
        !           106:  * and possibly adjust FSHIFT in "param.h" so that (FSHIFT >= CCPU_SHIFT).
        !           107:  *
        !           108:  * To estimate CCPU_SHIFT for exp(-1/20), the following formula was used:
        !           109:  *     1 - exp(-1/20) ~= 0.0487 ~= 0.0488 == 1 (fixed pt, *11* bits).
        !           110:  *
        !           111:  * If you dont want to bother with the faster/more-accurate formula, you
        !           112:  * can set CCPU_SHIFT to (FSHIFT + 1) which will use a slower/less-accurate
        !           113:  * (more general) method of calculating the %age of CPU used by a process.
        !           114:  */
        !           115: #define        CCPU_SHIFT      11
        !           116: 
        !           117: /*
        !           118:  * Recompute process priorities, once a second
        !           119:  */
        !           120: schedcpu()
        !           121: {
        !           122:        register fixpt_t b = get_b(averunnable[0]);
        !           123:        register struct proc *p;
        !           124:        register int s, a;
        !           125: 
        !           126:        wakeup((caddr_t)&lbolt);
        !           127:        for (p = allproc; p != NULL; p = p->p_nxt) {
        !           128:                if (p->p_time != 127)
        !           129:                        p->p_time++;
        !           130:                if (p->p_stat==SSLEEP || p->p_stat==SSTOP)
        !           131:                        if (p->p_slptime != 127)
        !           132:                                p->p_slptime++;
        !           133:                p->p_pctcpu = (p->p_pctcpu * ccpu) >> FSHIFT;
        !           134:                /*
        !           135:                 * If the process has slept the entire second,
        !           136:                 * stop recalculating its priority until it wakes up.
        !           137:                 */
        !           138:                if (p->p_slptime > 1)
        !           139:                        continue;
        !           140:                /*
        !           141:                 * p_pctcpu is only for ps.
        !           142:                 */
        !           143: #if    (FSHIFT >= CCPU_SHIFT)
        !           144:                p->p_pctcpu += (hz == 100)?
        !           145:                        ((fixpt_t) p->p_cpticks) << (FSHIFT - CCPU_SHIFT):
        !           146:                        100 * (((fixpt_t) p->p_cpticks)
        !           147:                                << (FSHIFT - CCPU_SHIFT)) / hz;
        !           148: #else
        !           149:                p->p_pctcpu += ((FSCALE - ccpu) *
        !           150:                        (p->p_cpticks * FSCALE / hz)) >> FSHIFT;
        !           151: #endif
        !           152:                p->p_cpticks = 0;
        !           153:                a = (int) get_pcpu(b, p->p_cpu) + p->p_nice;
        !           154:                if (a < 0)
        !           155:                        a = 0;
        !           156:                if (a > 255)
        !           157:                        a = 255;
        !           158:                p->p_cpu = a;
        !           159:                (void) setpri(p);
        !           160:                s = splhigh();  /* prevent state changes */
        !           161:                if (p->p_pri >= PUSER) {
        !           162: #define        PPQ     (128 / NQS)
        !           163:                        if ((p != u.u_procp || noproc) &&
        !           164:                            p->p_stat == SRUN &&
        !           165:                            (p->p_flag & SLOAD) &&
        !           166:                            (p->p_pri / PPQ) != (p->p_usrpri / PPQ)) {
        !           167:                                remrq(p);
        !           168:                                p->p_pri = p->p_usrpri;
        !           169:                                setrq(p);
        !           170:                        } else
        !           171:                                p->p_pri = p->p_usrpri;
        !           172:                }
        !           173:                splx(s);
        !           174:        }
        !           175:        vmmeter();
        !           176:        if (runin!=0) {
        !           177:                runin = 0;
        !           178:                wakeup((caddr_t)&runin);
        !           179:        }
        !           180:        if (bclnlist != NULL)
        !           181:                wakeup((caddr_t)&proc[2]);
        !           182:        timeout(schedcpu, (caddr_t)0, hz);
        !           183: }
        !           184: 
        !           185: /*
        !           186:  * Recalculate the priority of a process after it has slept for a while.
        !           187:  */
        !           188: updatepri(p)
        !           189:        register struct proc *p;
        !           190: {
        !           191:        register int a = p->p_cpu & 0377;
        !           192:        register fixpt_t b = get_b(averunnable[0]);
        !           193: 
        !           194:        p->p_slptime--;         /* the first time was done in schedcpu */
        !           195:        while (a && --p->p_slptime)
        !           196:                a = (int) get_pcpu(b, a) /* + p->p_nice */;
        !           197:        p->p_slptime = 0;
        !           198:        if (a < 0)
        !           199:                a = 0;
        !           200:        if (a > 255)
        !           201:                a = 255;
        !           202:        p->p_cpu = a;
        !           203:        (void) setpri(p);
        !           204: }
        !           205: 
        !           206: #define SQSIZE 0100    /* Must be power of 2 */
        !           207: #define HASH(x)        (( (int) x >> 5) & (SQSIZE-1))
        !           208: struct slpque {
        !           209:        struct proc *sq_head;
        !           210:        struct proc **sq_tailp;
        !           211: } slpque[SQSIZE];
        !           212: 
        !           213: /*
        !           214:  * General sleep call.
        !           215:  * Suspends current process until a wakeup is made on chan.
        !           216:  * The process will then be made runnable with priority pri.
        !           217:  * Sleeps at most timo/hz seconds (0 means no timeout).
        !           218:  * If pri includes PCATCH flag, signals are checked
        !           219:  * before and after sleeping, else signals are not checked.
        !           220:  * Returns 0 if awakened, EWOULDBLOCK if the timeout expires.
        !           221:  * If PCATCH is set and a signal needs to be delivered,
        !           222:  * ERESTART is returned if the current system call should be restarted
        !           223:  * if possible, and EINTR is returned if the system call should
        !           224:  * be interrupted by the signal (return EINTR).
        !           225:  */
        !           226: tsleep(chan, pri, wmesg, timo)
        !           227:        caddr_t chan;
        !           228:        int pri;
        !           229:        char *wmesg;
        !           230:        int timo;
        !           231: {
        !           232:        register struct proc *rp;
        !           233:        register struct slpque *qp;
        !           234:        register s;
        !           235:        int sig, catch = pri & PCATCH;
        !           236:        extern int cold;
        !           237:        int endtsleep();
        !           238: 
        !           239:        rp = u.u_procp;
        !           240:        s = splhigh();
        !           241:        if (cold || panicstr) {
        !           242:                /*
        !           243:                 * After a panic, or during autoconfiguration,
        !           244:                 * just give interrupts a chance, then just return;
        !           245:                 * don't run any other procs or panic below,
        !           246:                 * in case this is the idle process and already asleep.
        !           247:                 */
        !           248:                (void) spl0();
        !           249:                splx(s);
        !           250:                return (0);
        !           251:        }
        !           252: #ifdef DIAGNOSTIC
        !           253:        if (chan == 0 || rp->p_stat != SRUN || rp->p_rlink)
        !           254:                panic("tsleep");
        !           255: #endif
        !           256:        rp->p_wchan = chan;
        !           257:        rp->p_wmesg = wmesg;
        !           258:        rp->p_slptime = 0;
        !           259:        rp->p_pri = pri & PRIMASK;
        !           260:        qp = &slpque[HASH(chan)];
        !           261:        if (qp->sq_head == 0)
        !           262:                qp->sq_head = rp;
        !           263:        else
        !           264:                *qp->sq_tailp = rp;
        !           265:        *(qp->sq_tailp = &rp->p_link) = 0;
        !           266:        /*
        !           267:         * If we stop in CURSIG/issig(), wakeup may already
        !           268:         * have happened when we return.
        !           269:         * rp->p_wchan will then be 0.
        !           270:         */
        !           271:        if (catch) {
        !           272:                if (sig = CURSIG(rp)) {
        !           273:                        if (rp->p_wchan)
        !           274:                                unsleep(rp);
        !           275:                        rp->p_stat = SRUN;
        !           276:                        splx(s);
        !           277:                        if (u.u_sigintr & sigmask(sig))
        !           278:                                return (EINTR);
        !           279:                        return (ERESTART);
        !           280:                }
        !           281:                if (rp->p_wchan == 0) {
        !           282:                        splx(s);
        !           283:                        return (0);
        !           284:                }
        !           285:                rp->p_flag |= SSINTR;
        !           286:        }
        !           287:        rp->p_stat = SSLEEP;
        !           288:        if (timo)
        !           289:                timeout(endtsleep, (caddr_t)rp, timo);
        !           290:        (void) spl0();
        !           291:        u.u_ru.ru_nvcsw++;
        !           292:        swtch();
        !           293:        curpri = rp->p_usrpri;
        !           294:        splx(s);
        !           295:        rp->p_flag &= ~SSINTR;
        !           296:        if (rp->p_flag & STIMO) {
        !           297:                rp->p_flag &= ~STIMO;
        !           298:                return (EWOULDBLOCK);
        !           299:        }
        !           300:        if (timo)
        !           301:                untimeout(endtsleep, (caddr_t)rp);
        !           302:        if (catch && (sig = CURSIG(rp))) {
        !           303:                if (u.u_sigintr & sigmask(sig))
        !           304:                        return (EINTR);
        !           305:                return (ERESTART);
        !           306:        }
        !           307:        return (0);
        !           308: }
        !           309: 
        !           310: /*
        !           311:  * Implement timeout for tsleep.
        !           312:  * If process hasn't been awakened (wchan non-zero),
        !           313:  * set timeout flag and undo the sleep.  If proc
        !           314:  * is stopped, just unsleep so it will remain stopped.
        !           315:  */
        !           316: endtsleep(p)
        !           317:        register struct proc *p;
        !           318: {
        !           319:        int s = splhigh();
        !           320: 
        !           321:        if (p->p_wchan) {
        !           322:                if (p->p_stat == SSLEEP)
        !           323:                        setrun(p);
        !           324:                else
        !           325:                        unsleep(p);
        !           326:                p->p_flag |= STIMO;
        !           327:        }
        !           328:        splx(s);
        !           329: }
        !           330: 
        !           331: /*
        !           332:  * Short-term, non-interruptable sleep.
        !           333:  */
        !           334: sleep(chan, pri)
        !           335:        caddr_t chan;
        !           336:        int pri;
        !           337: {
        !           338:        register struct proc *rp;
        !           339:        register struct slpque *qp;
        !           340:        register s;
        !           341:        extern int cold;
        !           342: 
        !           343: #ifdef DIAGNOSTIC
        !           344:        if (pri > PZERO) {
        !           345:                printf("sleep called with pri %d > PZERO, wchan: %x\n",
        !           346:                        pri, chan);
        !           347:                panic("old sleep");
        !           348:        }
        !           349: #endif
        !           350:        rp = u.u_procp;
        !           351:        s = splhigh();
        !           352:        if (cold || panicstr) {
        !           353:                /*
        !           354:                 * After a panic, or during autoconfiguration,
        !           355:                 * just give interrupts a chance, then just return;
        !           356:                 * don't run any other procs or panic below,
        !           357:                 * in case this is the idle process and already asleep.
        !           358:                 */
        !           359:                (void) spl0();
        !           360:                splx(s);
        !           361:                return;
        !           362:        }
        !           363: #ifdef DIAGNOSTIC
        !           364:        if (chan==0 || rp->p_stat != SRUN || rp->p_rlink)
        !           365:                panic("sleep");
        !           366: #endif
        !           367:        rp->p_wchan = chan;
        !           368:        rp->p_wmesg = NULL;
        !           369:        rp->p_slptime = 0;
        !           370:        rp->p_pri = pri;
        !           371:        qp = &slpque[HASH(chan)];
        !           372:        if (qp->sq_head == 0)
        !           373:                qp->sq_head = rp;
        !           374:        else
        !           375:                *qp->sq_tailp = rp;
        !           376:        *(qp->sq_tailp = &rp->p_link) = 0;
        !           377:        rp->p_stat = SSLEEP;
        !           378:        (void) spl0();
        !           379:        u.u_ru.ru_nvcsw++;
        !           380:        swtch();
        !           381:        curpri = rp->p_usrpri;
        !           382:        splx(s);
        !           383: }
        !           384: 
        !           385: /*
        !           386:  * Remove a process from its wait queue
        !           387:  */
        !           388: unsleep(p)
        !           389:        register struct proc *p;
        !           390: {
        !           391:        register struct slpque *qp;
        !           392:        register struct proc **hp;
        !           393:        int s;
        !           394: 
        !           395:        s = splhigh();
        !           396:        if (p->p_wchan) {
        !           397:                hp = &(qp = &slpque[HASH(p->p_wchan)])->sq_head;
        !           398:                while (*hp != p)
        !           399:                        hp = &(*hp)->p_link;
        !           400:                *hp = p->p_link;
        !           401:                if (qp->sq_tailp == &p->p_link)
        !           402:                        qp->sq_tailp = hp;
        !           403:                p->p_wchan = 0;
        !           404:        }
        !           405:        splx(s);
        !           406: }
        !           407: 
        !           408: /*
        !           409:  * Wake up all processes sleeping on chan.
        !           410:  */
        !           411: wakeup(chan)
        !           412:        register caddr_t chan;
        !           413: {
        !           414:        register struct slpque *qp;
        !           415:        register struct proc *p, **q;
        !           416:        int s;
        !           417: 
        !           418:        s = splhigh();
        !           419:        qp = &slpque[HASH(chan)];
        !           420: restart:
        !           421:        for (q = &qp->sq_head; p = *q; ) {
        !           422: #ifdef DIAGNOSTIC
        !           423:                if (p->p_rlink || p->p_stat != SSLEEP && p->p_stat != SSTOP)
        !           424:                        panic("wakeup");
        !           425: #endif
        !           426:                if (p->p_wchan==chan) {
        !           427:                        p->p_wchan = 0;
        !           428:                        *q = p->p_link;
        !           429:                        if (qp->sq_tailp == &p->p_link)
        !           430:                                qp->sq_tailp = q;
        !           431:                        if (p->p_stat == SSLEEP) {
        !           432:                                /* OPTIMIZED INLINE EXPANSION OF setrun(p) */
        !           433:                                if (p->p_slptime > 1)
        !           434:                                        updatepri(p);
        !           435:                                p->p_stat = SRUN;
        !           436:                                if (p->p_flag & SLOAD)
        !           437:                                        setrq(p);
        !           438:                                /*
        !           439:                                 * Since curpri is a usrpri,
        !           440:                                 * p->p_pri is always better than curpri.
        !           441:                                 */
        !           442:                                runrun++;
        !           443:                                aston();
        !           444:                                if ((p->p_flag&SLOAD) == 0) {
        !           445:                                        if (runout != 0) {
        !           446:                                                runout = 0;
        !           447:                                                wakeup((caddr_t)&runout);
        !           448:                                        }
        !           449:                                        wantin++;
        !           450:                                }
        !           451:                                /* END INLINE EXPANSION */
        !           452:                                goto restart;
        !           453:                        }
        !           454:                } else
        !           455:                        q = &p->p_link;
        !           456:        }
        !           457:        splx(s);
        !           458: }
        !           459: 
        !           460: /*
        !           461:  * Initialize the (doubly-linked) run queues
        !           462:  * to be empty.
        !           463:  */
        !           464: rqinit()
        !           465: {
        !           466:        register int i;
        !           467: 
        !           468:        for (i = 0; i < NQS; i++)
        !           469:                qs[i].ph_link = qs[i].ph_rlink = (struct proc *)&qs[i];
        !           470: }
        !           471: 
        !           472: /*
        !           473:  * Set the process running;
        !           474:  * arrange for it to be swapped in if necessary.
        !           475:  */
        !           476: setrun(p)
        !           477:        register struct proc *p;
        !           478: {
        !           479:        register int s;
        !           480: 
        !           481:        s = splhigh();
        !           482:        switch (p->p_stat) {
        !           483: 
        !           484:        case 0:
        !           485:        case SWAIT:
        !           486:        case SRUN:
        !           487:        case SZOMB:
        !           488:        default:
        !           489:                panic("setrun");
        !           490: 
        !           491:        case SSTOP:
        !           492:        case SSLEEP:
        !           493:                unsleep(p);             /* e.g. when sending signals */
        !           494:                break;
        !           495: 
        !           496:        case SIDL:
        !           497:                break;
        !           498:        }
        !           499:        p->p_stat = SRUN;
        !           500:        if (p->p_flag & SLOAD)
        !           501:                setrq(p);
        !           502:        splx(s);
        !           503:        if (p->p_slptime > 1)
        !           504:                updatepri(p);
        !           505:        if (p->p_pri < curpri) {
        !           506:                runrun++;
        !           507:                aston();
        !           508:        }
        !           509:        if ((p->p_flag&SLOAD) == 0) {
        !           510:                if (runout != 0) {
        !           511:                        runout = 0;
        !           512:                        wakeup((caddr_t)&runout);
        !           513:                }
        !           514:                wantin++;
        !           515:        }
        !           516: }
        !           517: 
        !           518: /*
        !           519:  * Set user priority.
        !           520:  * The rescheduling flag (runrun)
        !           521:  * is set if the priority is better
        !           522:  * than the currently running process.
        !           523:  */
        !           524: setpri(pp)
        !           525:        register struct proc *pp;
        !           526: {
        !           527:        register int p;
        !           528: 
        !           529:        p = (pp->p_cpu & 0377)/4;
        !           530:        p += PUSER + 2 * pp->p_nice;
        !           531:        if (pp->p_rssize > pp->p_maxrss && freemem < desfree)
        !           532:                p += 2*4;       /* effectively, nice(4) */
        !           533:        if (p > 127)
        !           534:                p = 127;
        !           535:        if (p < curpri) {
        !           536:                runrun++;
        !           537:                aston();
        !           538:        }
        !           539:        pp->p_usrpri = p;
        !           540:        return (p);
        !           541: }

This archive runs on limited infrastructure. Preserving old code on modern bandwidth. Automated agents are requested to crawl responsibly.