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Annotation of Net2/kern/kern_clock.c, revision 1.1

1.1     ! root        1: /*-
        !             2:  * Copyright (c) 1982, 1986, 1991 The Regents of the University of California.
        !             3:  * All rights reserved.
        !             4:  *
        !             5:  * Redistribution and use in source and binary forms, with or without
        !             6:  * modification, are permitted provided that the following conditions
        !             7:  * are met:
        !             8:  * 1. Redistributions of source code must retain the above copyright
        !             9:  *    notice, this list of conditions and the following disclaimer.
        !            10:  * 2. Redistributions in binary form must reproduce the above copyright
        !            11:  *    notice, this list of conditions and the following disclaimer in the
        !            12:  *    documentation and/or other materials provided with the distribution.
        !            13:  * 3. All advertising materials mentioning features or use of this software
        !            14:  *    must display the following acknowledgement:
        !            15:  *     This product includes software developed by the University of
        !            16:  *     California, Berkeley and its contributors.
        !            17:  * 4. Neither the name of the University nor the names of its contributors
        !            18:  *    may be used to endorse or promote products derived from this software
        !            19:  *    without specific prior written permission.
        !            20:  *
        !            21:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
        !            22:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
        !            23:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
        !            24:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
        !            25:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
        !            26:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
        !            27:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
        !            28:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
        !            29:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
        !            30:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
        !            31:  * SUCH DAMAGE.
        !            32:  *
        !            33:  *     @(#)kern_clock.c        7.16 (Berkeley) 5/9/91
        !            34:  */
        !            35: 
        !            36: #include "param.h"
        !            37: #include "systm.h"
        !            38: #include "dkstat.h"
        !            39: #include "callout.h"
        !            40: #include "kernel.h"
        !            41: #include "proc.h"
        !            42: #include "resourcevar.h"
        !            43: 
        !            44: #include "machine/cpu.h"
        !            45: 
        !            46: #ifdef GPROF
        !            47: #include "gprof.h"
        !            48: #endif
        !            49: 
        !            50: /*
        !            51:  * Clock handling routines.
        !            52:  *
        !            53:  * This code is written to operate with two timers which run
        !            54:  * independently of each other. The main clock, running at hz
        !            55:  * times per second, is used to do scheduling and timeout calculations.
        !            56:  * The second timer does resource utilization estimation statistically
        !            57:  * based on the state of the machine phz times a second. Both functions
        !            58:  * can be performed by a single clock (ie hz == phz), however the 
        !            59:  * statistics will be much more prone to errors. Ideally a machine
        !            60:  * would have separate clocks measuring time spent in user state, system
        !            61:  * state, interrupt state, and idle state. These clocks would allow a non-
        !            62:  * approximate measure of resource utilization.
        !            63:  */
        !            64: 
        !            65: /*
        !            66:  * TODO:
        !            67:  *     time of day, system/user timing, timeouts, profiling on separate timers
        !            68:  *     allocate more timeout table slots when table overflows.
        !            69:  */
        !            70: 
        !            71: /*
        !            72:  * Bump a timeval by a small number of usec's.
        !            73:  */
        !            74: #define BUMPTIME(t, usec) { \
        !            75:        register struct timeval *tp = (t); \
        !            76:  \
        !            77:        tp->tv_usec += (usec); \
        !            78:        if (tp->tv_usec >= 1000000) { \
        !            79:                tp->tv_usec -= 1000000; \
        !            80:                tp->tv_sec++; \
        !            81:        } \
        !            82: }
        !            83: 
        !            84: /*
        !            85:  * The hz hardware interval timer.
        !            86:  * We update the events relating to real time.
        !            87:  * If this timer is also being used to gather statistics,
        !            88:  * we run through the statistics gathering routine as well.
        !            89:  */
        !            90: hardclock(frame)
        !            91:        clockframe frame;
        !            92: {
        !            93:        register struct callout *p1;
        !            94:        register struct proc *p = curproc;
        !            95:        register struct pstats *pstats;
        !            96:        register int s;
        !            97:        int needsoft = 0;
        !            98:        extern int tickdelta;
        !            99:        extern long timedelta;
        !           100: 
        !           101:        /*
        !           102:         * Update real-time timeout queue.
        !           103:         * At front of queue are some number of events which are ``due''.
        !           104:         * The time to these is <= 0 and if negative represents the
        !           105:         * number of ticks which have passed since it was supposed to happen.
        !           106:         * The rest of the q elements (times > 0) are events yet to happen,
        !           107:         * where the time for each is given as a delta from the previous.
        !           108:         * Decrementing just the first of these serves to decrement the time
        !           109:         * to all events.
        !           110:         */
        !           111:        p1 = calltodo.c_next;
        !           112:        while (p1) {
        !           113:                if (--p1->c_time > 0)
        !           114:                        break;
        !           115:                needsoft = 1;
        !           116:                if (p1->c_time == 0)
        !           117:                        break;
        !           118:                p1 = p1->c_next;
        !           119:        }
        !           120: 
        !           121:        /*
        !           122:         * Curproc (now in p) is null if no process is running.
        !           123:         * We assume that curproc is set in user mode!
        !           124:         */
        !           125:        if (p)
        !           126:                pstats = p->p_stats;
        !           127:        /*
        !           128:         * Charge the time out based on the mode the cpu is in.
        !           129:         * Here again we fudge for the lack of proper interval timers
        !           130:         * assuming that the current state has been around at least
        !           131:         * one tick.
        !           132:         */
        !           133:        if (CLKF_USERMODE(&frame)) {
        !           134:                if (pstats->p_prof.pr_scale)
        !           135:                        needsoft = 1;
        !           136:                /*
        !           137:                 * CPU was in user state.  Increment
        !           138:                 * user time counter, and process process-virtual time
        !           139:                 * interval timer. 
        !           140:                 */
        !           141:                BUMPTIME(&p->p_utime, tick);
        !           142:                if (timerisset(&pstats->p_timer[ITIMER_VIRTUAL].it_value) &&
        !           143:                    itimerdecr(&pstats->p_timer[ITIMER_VIRTUAL], tick) == 0)
        !           144:                        psignal(p, SIGVTALRM);
        !           145:        } else {
        !           146:                /*
        !           147:                 * CPU was in system state.
        !           148:                 */
        !           149:                if (p)
        !           150:                        BUMPTIME(&p->p_stime, tick);
        !           151:        }
        !           152: 
        !           153:        /*
        !           154:         * If the cpu is currently scheduled to a process, then
        !           155:         * charge it with resource utilization for a tick, updating
        !           156:         * statistics which run in (user+system) virtual time,
        !           157:         * such as the cpu time limit and profiling timers.
        !           158:         * This assumes that the current process has been running
        !           159:         * the entire last tick.
        !           160:         */
        !           161:        if (p) {
        !           162:                if ((p->p_utime.tv_sec+p->p_stime.tv_sec+1) >
        !           163:                    p->p_rlimit[RLIMIT_CPU].rlim_cur) {
        !           164:                        psignal(p, SIGXCPU);
        !           165:                        if (p->p_rlimit[RLIMIT_CPU].rlim_cur <
        !           166:                            p->p_rlimit[RLIMIT_CPU].rlim_max)
        !           167:                                p->p_rlimit[RLIMIT_CPU].rlim_cur += 5;
        !           168:                }
        !           169:                if (timerisset(&pstats->p_timer[ITIMER_PROF].it_value) &&
        !           170:                    itimerdecr(&pstats->p_timer[ITIMER_PROF], tick) == 0)
        !           171:                        psignal(p, SIGPROF);
        !           172: 
        !           173:                /*
        !           174:                 * We adjust the priority of the current process.
        !           175:                 * The priority of a process gets worse as it accumulates
        !           176:                 * CPU time.  The cpu usage estimator (p_cpu) is increased here
        !           177:                 * and the formula for computing priorities (in kern_synch.c)
        !           178:                 * will compute a different value each time the p_cpu increases
        !           179:                 * by 4.  The cpu usage estimator ramps up quite quickly when
        !           180:                 * the process is running (linearly), and decays away
        !           181:                 * exponentially, * at a rate which is proportionally slower
        !           182:                 * when the system is busy.  The basic principal is that the
        !           183:                 * system will 90% forget that a process used a lot of CPU
        !           184:                 * time in 5*loadav seconds.  This causes the system to favor
        !           185:                 * processes which haven't run much recently, and to
        !           186:                 * round-robin among other processes.
        !           187:                 */
        !           188:                p->p_cpticks++;
        !           189:                if (++p->p_cpu == 0)
        !           190:                        p->p_cpu--;
        !           191:                if ((p->p_cpu&3) == 0) {
        !           192:                        setpri(p);
        !           193:                        if (p->p_pri >= PUSER)
        !           194:                                p->p_pri = p->p_usrpri;
        !           195:                }
        !           196:        }
        !           197: 
        !           198:        /*
        !           199:         * If the alternate clock has not made itself known then
        !           200:         * we must gather the statistics.
        !           201:         */
        !           202:        if (phz == 0)
        !           203:                gatherstats(&frame);
        !           204: 
        !           205:        /*
        !           206:         * Increment the time-of-day, and schedule
        !           207:         * processing of the callouts at a very low cpu priority,
        !           208:         * so we don't keep the relatively high clock interrupt
        !           209:         * priority any longer than necessary.
        !           210:         */
        !           211:        if (timedelta == 0)
        !           212:                BUMPTIME(&time, tick)
        !           213:        else {
        !           214:                register delta;
        !           215: 
        !           216:                if (timedelta < 0) {
        !           217:                        delta = tick - tickdelta;
        !           218:                        timedelta += tickdelta;
        !           219:                } else {
        !           220:                        delta = tick + tickdelta;
        !           221:                        timedelta -= tickdelta;
        !           222:                }
        !           223:                BUMPTIME(&time, delta);
        !           224:        }
        !           225:        if (needsoft) {
        !           226:                if (CLKF_BASEPRI(&frame)) {
        !           227:                        /*
        !           228:                         * Save the overhead of a software interrupt;
        !           229:                         * it will happen as soon as we return, so do it now.
        !           230:                         */
        !           231:                        (void) splsoftclock();
        !           232:                        softclock(frame);
        !           233:                } else
        !           234:                        setsoftclock();
        !           235:        }
        !           236: }
        !           237: 
        !           238: int    dk_ndrive = DK_NDRIVE;
        !           239: /*
        !           240:  * Gather statistics on resource utilization.
        !           241:  *
        !           242:  * We make a gross assumption: that the system has been in the
        !           243:  * state it is in (user state, kernel state, interrupt state,
        !           244:  * or idle state) for the entire last time interval, and
        !           245:  * update statistics accordingly.
        !           246:  */
        !           247: gatherstats(framep)
        !           248:        clockframe *framep;
        !           249: {
        !           250:        register int cpstate, s;
        !           251: 
        !           252:        /*
        !           253:         * Determine what state the cpu is in.
        !           254:         */
        !           255:        if (CLKF_USERMODE(framep)) {
        !           256:                /*
        !           257:                 * CPU was in user state.
        !           258:                 */
        !           259:                if (curproc->p_nice > NZERO)
        !           260:                        cpstate = CP_NICE;
        !           261:                else
        !           262:                        cpstate = CP_USER;
        !           263:        } else {
        !           264:                /*
        !           265:                 * CPU was in system state.  If profiling kernel
        !           266:                 * increment a counter.  If no process is running
        !           267:                 * then this is a system tick if we were running
        !           268:                 * at a non-zero IPL (in a driver).  If a process is running,
        !           269:                 * then we charge it with system time even if we were
        !           270:                 * at a non-zero IPL, since the system often runs
        !           271:                 * this way during processing of system calls.
        !           272:                 * This is approximate, but the lack of true interval
        !           273:                 * timers makes doing anything else difficult.
        !           274:                 */
        !           275:                cpstate = CP_SYS;
        !           276:                if (curproc == NULL && CLKF_BASEPRI(framep))
        !           277:                        cpstate = CP_IDLE;
        !           278: #ifdef GPROF
        !           279:                s = CLKF_PC(framep) - s_lowpc;
        !           280:                if (profiling < 2 && s < s_textsize)
        !           281:                        kcount[s / (HISTFRACTION * sizeof (*kcount))]++;
        !           282: #endif
        !           283:        }
        !           284:        /*
        !           285:         * We maintain statistics shown by user-level statistics
        !           286:         * programs:  the amount of time in each cpu state, and
        !           287:         * the amount of time each of DK_NDRIVE ``drives'' is busy.
        !           288:         */
        !           289:        cp_time[cpstate]++;
        !           290:        for (s = 0; s < DK_NDRIVE; s++)
        !           291:                if (dk_busy&(1<<s))
        !           292:                        dk_time[s]++;
        !           293: }
        !           294: 
        !           295: /*
        !           296:  * Software priority level clock interrupt.
        !           297:  * Run periodic events from timeout queue.
        !           298:  */
        !           299: /*ARGSUSED*/
        !           300: softclock(frame)
        !           301:        clockframe frame;
        !           302: {
        !           303: 
        !           304:        for (;;) {
        !           305:                register struct callout *p1;
        !           306:                register caddr_t arg;
        !           307:                register int (*func)();
        !           308:                register int a, s;
        !           309: 
        !           310:                s = splhigh();
        !           311:                if ((p1 = calltodo.c_next) == 0 || p1->c_time > 0) {
        !           312:                        splx(s);
        !           313:                        break;
        !           314:                }
        !           315:                arg = p1->c_arg; func = p1->c_func; a = p1->c_time;
        !           316:                calltodo.c_next = p1->c_next;
        !           317:                p1->c_next = callfree;
        !           318:                callfree = p1;
        !           319:                splx(s);
        !           320:                (*func)(arg, a);
        !           321:        }
        !           322:        /*
        !           323:         * If trapped user-mode and profiling, give it
        !           324:         * a profiling tick.
        !           325:         */
        !           326:        if (CLKF_USERMODE(&frame)) {
        !           327:                register struct proc *p = curproc;
        !           328: 
        !           329:                if (p->p_stats->p_prof.pr_scale)
        !           330:                        profile_tick(p, &frame);
        !           331:                /*
        !           332:                 * Check to see if process has accumulated
        !           333:                 * more than 10 minutes of user time.  If so
        !           334:                 * reduce priority to give others a chance.
        !           335:                 */
        !           336:                if (p->p_ucred->cr_uid && p->p_nice == NZERO &&
        !           337:                    p->p_utime.tv_sec > 10 * 60) {
        !           338:                        p->p_nice = NZERO + 4;
        !           339:                        setpri(p);
        !           340:                        p->p_pri = p->p_usrpri;
        !           341:                }
        !           342:        }
        !           343: }
        !           344: 
        !           345: /*
        !           346:  * Arrange that (*func)(arg) is called in t/hz seconds.
        !           347:  */
        !           348: timeout(func, arg, t)
        !           349:        int (*func)();
        !           350:        caddr_t arg;
        !           351:        register int t;
        !           352: {
        !           353:        register struct callout *p1, *p2, *pnew;
        !           354:        register int s = splhigh();
        !           355: 
        !           356:        if (t <= 0)
        !           357:                t = 1;
        !           358:        pnew = callfree;
        !           359:        if (pnew == NULL)
        !           360:                panic("timeout table overflow");
        !           361:        callfree = pnew->c_next;
        !           362:        pnew->c_arg = arg;
        !           363:        pnew->c_func = func;
        !           364:        for (p1 = &calltodo; (p2 = p1->c_next) && p2->c_time < t; p1 = p2)
        !           365:                if (p2->c_time > 0)
        !           366:                        t -= p2->c_time;
        !           367:        p1->c_next = pnew;
        !           368:        pnew->c_next = p2;
        !           369:        pnew->c_time = t;
        !           370:        if (p2)
        !           371:                p2->c_time -= t;
        !           372:        splx(s);
        !           373: }
        !           374: 
        !           375: /*
        !           376:  * untimeout is called to remove a function timeout call
        !           377:  * from the callout structure.
        !           378:  */
        !           379: untimeout(func, arg)
        !           380:        int (*func)();
        !           381:        caddr_t arg;
        !           382: {
        !           383:        register struct callout *p1, *p2;
        !           384:        register int s;
        !           385: 
        !           386:        s = splhigh();
        !           387:        for (p1 = &calltodo; (p2 = p1->c_next) != 0; p1 = p2) {
        !           388:                if (p2->c_func == func && p2->c_arg == arg) {
        !           389:                        if (p2->c_next && p2->c_time > 0)
        !           390:                                p2->c_next->c_time += p2->c_time;
        !           391:                        p1->c_next = p2->c_next;
        !           392:                        p2->c_next = callfree;
        !           393:                        callfree = p2;
        !           394:                        break;
        !           395:                }
        !           396:        }
        !           397:        splx(s);
        !           398: }
        !           399: 
        !           400: /*
        !           401:  * Compute number of hz until specified time.
        !           402:  * Used to compute third argument to timeout() from an
        !           403:  * absolute time.
        !           404:  */
        !           405: hzto(tv)
        !           406:        struct timeval *tv;
        !           407: {
        !           408:        register long ticks;
        !           409:        register long sec;
        !           410:        int s = splhigh();
        !           411: 
        !           412:        /*
        !           413:         * If number of milliseconds will fit in 32 bit arithmetic,
        !           414:         * then compute number of milliseconds to time and scale to
        !           415:         * ticks.  Otherwise just compute number of hz in time, rounding
        !           416:         * times greater than representible to maximum value.
        !           417:         *
        !           418:         * Delta times less than 25 days can be computed ``exactly''.
        !           419:         * Maximum value for any timeout in 10ms ticks is 250 days.
        !           420:         */
        !           421:        sec = tv->tv_sec - time.tv_sec;
        !           422:        if (sec <= 0x7fffffff / 1000 - 1000)
        !           423:                ticks = ((tv->tv_sec - time.tv_sec) * 1000 +
        !           424:                        (tv->tv_usec - time.tv_usec) / 1000) / (tick / 1000);
        !           425:        else if (sec <= 0x7fffffff / hz)
        !           426:                ticks = sec * hz;
        !           427:        else
        !           428:                ticks = 0x7fffffff;
        !           429:        splx(s);
        !           430:        return (ticks);
        !           431: }

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