FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_clock.c

     /*-
      * Copyright (c) 1982, 1986, 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_clock.c        8.5 (Berkeley) 1/21/94
     * $FreeBSD: releng/5.1/sys/kern/kern_clock.c 114216 2003-04-29 13:36:06Z kan $
     */
    
    #include "opt_ntp.h"
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/callout.h>
    #include <sys/kernel.h>
    #include <sys/lock.h>
    #include <sys/ktr.h>
    #include <sys/mutex.h>
    #include <sys/proc.h>
    #include <sys/resource.h>
    #include <sys/resourcevar.h>
    #include <sys/sched.h>
    #include <sys/signalvar.h>
    #include <sys/smp.h>
    #include <vm/vm.h>
    #include <vm/pmap.h>
    #include <vm/vm_map.h>
    #include <sys/sysctl.h>
    #include <sys/bus.h>
    #include <sys/interrupt.h>
    #include <sys/limits.h>
    #include <sys/timetc.h>
    
    #include <machine/cpu.h>
    
    #ifdef GPROF
    #include <sys/gmon.h>
    #endif
    
    #ifdef DEVICE_POLLING
    extern void hardclock_device_poll(void);
    #endif /* DEVICE_POLLING */
    
    static void initclocks(void *dummy);
    SYSINIT(clocks, SI_SUB_CLOCKS, SI_ORDER_FIRST, initclocks, NULL)
    
    /* Some of these don't belong here, but it's easiest to concentrate them. */
    long cp_time[CPUSTATES];
    
    SYSCTL_OPAQUE(_kern, OID_AUTO, cp_time, CTLFLAG_RD, &cp_time, sizeof(cp_time),
        "LU", "CPU time statistics");
    
    /*
     * Clock handling routines.
     *
     * This code is written to operate with two timers that run independently of
     * each other.
     *
     * The main timer, running hz times per second, is used to trigger interval
     * timers, timeouts and rescheduling as needed.
     *
     * The second timer handles kernel and user profiling,
     * and does resource use estimation.  If the second timer is programmable,
     * it is randomized to avoid aliasing between the two clocks.  For example,
     * the randomization prevents an adversary from always giving up the cpu
     * just before its quantum expires.  Otherwise, it would never accumulate
     * cpu ticks.  The mean frequency of the second timer is stathz.
    *
    * If no second timer exists, stathz will be zero; in this case we drive
    * profiling and statistics off the main clock.  This WILL NOT be accurate;
    * do not do it unless absolutely necessary.
    *
    * The statistics clock may (or may not) be run at a higher rate while
    * profiling.  This profile clock runs at profhz.  We require that profhz
    * be an integral multiple of stathz.
    *
    * If the statistics clock is running fast, it must be divided by the ratio
    * profhz/stathz for statistics.  (For profiling, every tick counts.)
    *
    * Time-of-day is maintained using a "timecounter", which may or may
    * not be related to the hardware generating the above mentioned
    * interrupts.
    */
   
   int     stathz;
   int     profhz;
   int     profprocs;
   int     ticks;
   int     psratio;
   
   /*
    * Initialize clock frequencies and start both clocks running.
    */
   /* ARGSUSED*/
   static void
   initclocks(dummy)
           void *dummy;
   {
           register int i;
   
           /*
            * Set divisors to 1 (normal case) and let the machine-specific
            * code do its bit.
            */
           cpu_initclocks();
   
           /*
            * Compute profhz/stathz, and fix profhz if needed.
            */
           i = stathz ? stathz : hz;
           if (profhz == 0)
                   profhz = i;
           psratio = profhz / i;
   }
   
   /*
    * Each time the real-time timer fires, this function is called on all CPUs.
    * Note that hardclock() calls hardclock_process() for the boot CPU, so only
    * the other CPUs in the system need to call this function.
    */
   void
   hardclock_process(frame)
           register struct clockframe *frame;
   {
           struct pstats *pstats;
           struct thread *td = curthread;
           struct proc *p = td->td_proc;
   
           /*
            * Run current process's virtual and profile time, as needed.
            */
           mtx_lock_spin_flags(&sched_lock, MTX_QUIET);
           if (p->p_flag & P_THREADED) {
                   /* XXXKSE What to do? */
           } else {
                   pstats = p->p_stats;
                   if (CLKF_USERMODE(frame) &&
                       timevalisset(&pstats->p_timer[ITIMER_VIRTUAL].it_value) &&
                       itimerdecr(&pstats->p_timer[ITIMER_VIRTUAL], tick) == 0) {
                           p->p_sflag |= PS_ALRMPEND;
                           td->td_flags |= TDF_ASTPENDING;
                   }
                   if (timevalisset(&pstats->p_timer[ITIMER_PROF].it_value) &&
                       itimerdecr(&pstats->p_timer[ITIMER_PROF], tick) == 0) {
                           p->p_sflag |= PS_PROFPEND;
                           td->td_flags |= TDF_ASTPENDING;
                   }
           }
           mtx_unlock_spin_flags(&sched_lock, MTX_QUIET);
   }
   
   /*
    * The real-time timer, interrupting hz times per second.
    */
   void
   hardclock(frame)
           register struct clockframe *frame;
   {
           int need_softclock = 0;
   
           CTR0(KTR_CLK, "hardclock fired");
           hardclock_process(frame);
   
           tc_ticktock();
           /*
            * If no separate statistics clock is available, run it from here.
            *
            * XXX: this only works for UP
            */
           if (stathz == 0) {
                   profclock(frame);
                   statclock(frame);
           }
   
   #ifdef DEVICE_POLLING
           hardclock_device_poll();        /* this is very short and quick */
   #endif /* DEVICE_POLLING */
   
           /*
            * Process callouts at a very low cpu priority, so we don't keep the
            * relatively high clock interrupt priority any longer than necessary.
            */
           mtx_lock_spin_flags(&callout_lock, MTX_QUIET);
           ticks++;
           if (TAILQ_FIRST(&callwheel[ticks & callwheelmask]) != NULL) {
                   need_softclock = 1;
           } else if (softticks + 1 == ticks)
                   ++softticks;
           mtx_unlock_spin_flags(&callout_lock, MTX_QUIET);
   
           /*
            * swi_sched acquires sched_lock, so we don't want to call it with
            * callout_lock held; incorrect locking order.
            */
           if (need_softclock)
                   swi_sched(softclock_ih, 0);
   }
   
   /*
    * Compute number of ticks in the specified amount of time.
    */
   int
   tvtohz(tv)
           struct timeval *tv;
   {
           register unsigned long ticks;
           register long sec, usec;
   
           /*
            * If the number of usecs in the whole seconds part of the time
            * difference fits in a long, then the total number of usecs will
            * fit in an unsigned long.  Compute the total and convert it to
            * ticks, rounding up and adding 1 to allow for the current tick
            * to expire.  Rounding also depends on unsigned long arithmetic
            * to avoid overflow.
            *
            * Otherwise, if the number of ticks in the whole seconds part of
            * the time difference fits in a long, then convert the parts to
            * ticks separately and add, using similar rounding methods and
            * overflow avoidance.  This method would work in the previous
            * case but it is slightly slower and assumes that hz is integral.
            *
            * Otherwise, round the time difference down to the maximum
            * representable value.
            *
            * If ints have 32 bits, then the maximum value for any timeout in
            * 10ms ticks is 248 days.
            */
           sec = tv->tv_sec;
           usec = tv->tv_usec;
           if (usec < 0) {
                   sec--;
                   usec += 1000000;
           }
           if (sec < 0) {
   #ifdef DIAGNOSTIC
                   if (usec > 0) {
                           sec++;
                           usec -= 1000000;
                   }
                   printf("tvotohz: negative time difference %ld sec %ld usec\n",
                          sec, usec);
   #endif
                   ticks = 1;
           } else if (sec <= LONG_MAX / 1000000)
                   ticks = (sec * 1000000 + (unsigned long)usec + (tick - 1))
                           / tick + 1;
           else if (sec <= LONG_MAX / hz)
                   ticks = sec * hz
                           + ((unsigned long)usec + (tick - 1)) / tick + 1;
           else
                   ticks = LONG_MAX;
           if (ticks > INT_MAX)
                   ticks = INT_MAX;
           return ((int)ticks);
   }
   
   /*
    * Start profiling on a process.
    *
    * Kernel profiling passes proc0 which never exits and hence
    * keeps the profile clock running constantly.
    */
   void
   startprofclock(p)
           register struct proc *p;
   {
   
           /*
            * XXX; Right now sched_lock protects statclock(), but perhaps
            * it should be protected later on by a time_lock, which would
            * cover psdiv, etc. as well.
            */
           PROC_LOCK_ASSERT(p, MA_OWNED);
           if (p->p_flag & P_STOPPROF)
                   return;
           if ((p->p_flag & P_PROFIL) == 0) {
                   mtx_lock_spin(&sched_lock);
                   p->p_flag |= P_PROFIL;
                   if (++profprocs == 1)
                           cpu_startprofclock();
                   mtx_unlock_spin(&sched_lock);
           }
   }
   
   /*
    * Stop profiling on a process.
    */
   void
   stopprofclock(p)
           register struct proc *p;
   {
   
           PROC_LOCK_ASSERT(p, MA_OWNED);
           if (p->p_flag & P_PROFIL) {
                   if (p->p_profthreads != 0) {
                           p->p_flag |= P_STOPPROF;
                           while (p->p_profthreads != 0)
                                   msleep(&p->p_profthreads, &p->p_mtx, PPAUSE,
                                       "stopprof", NULL);
                           p->p_flag &= ~P_STOPPROF;
                   }
                   mtx_lock_spin(&sched_lock);
                   p->p_flag &= ~P_PROFIL;
                   if (--profprocs == 0)
                           cpu_stopprofclock();
                   mtx_unlock_spin(&sched_lock);
           }
   }
   
   /*
    * Statistics clock.  Grab profile sample, and if divider reaches 0,
    * do process and kernel statistics.  Most of the statistics are only
    * used by user-level statistics programs.  The main exceptions are
    * ke->ke_uticks, p->p_sticks, p->p_iticks, and p->p_estcpu.
    * This should be called by all active processors.
    */
   void
   statclock(frame)
           register struct clockframe *frame;
   {
           struct pstats *pstats;
           struct rusage *ru;
           struct vmspace *vm;
           struct thread *td;
           struct kse *ke;
           struct proc *p;
           long rss;
   
           td = curthread;
           p = td->td_proc;
   
           mtx_lock_spin_flags(&sched_lock, MTX_QUIET);
           ke = td->td_kse;
           if (CLKF_USERMODE(frame)) {
                   /*
                    * Charge the time as appropriate.
                    */
                   if (p->p_flag & P_THREADED)
                           thread_statclock(1);
                   p->p_uticks++;
                   if (ke->ke_ksegrp->kg_nice > NZERO)
                           cp_time[CP_NICE]++;
                   else
                           cp_time[CP_USER]++;
           } else {
                   /*
                    * Came from kernel mode, so we were:
                    * - handling an interrupt,
                    * - doing syscall or trap work on behalf of the current
                    *   user process, or
                    * - spinning in the idle loop.
                    * Whichever it is, charge the time as appropriate.
                    * Note that we charge interrupts to the current process,
                    * regardless of whether they are ``for'' that process,
                    * so that we know how much of its real time was spent
                    * in ``non-process'' (i.e., interrupt) work.
                    */
                   if ((td->td_ithd != NULL) || td->td_intr_nesting_level >= 2) {
                           p->p_iticks++;
                           cp_time[CP_INTR]++;
                   } else {
                           if (p->p_flag & P_THREADED)
                                   thread_statclock(0);
                           td->td_sticks++;
                           p->p_sticks++;
                           if (p != PCPU_GET(idlethread)->td_proc)
                                   cp_time[CP_SYS]++;
                           else
                                   cp_time[CP_IDLE]++;
                   }
           }
   
           sched_clock(ke);
   
           /* Update resource usage integrals and maximums. */
           if ((pstats = p->p_stats) != NULL &&
               (ru = &pstats->p_ru) != NULL &&
               (vm = p->p_vmspace) != NULL) {
                   ru->ru_ixrss += pgtok(vm->vm_tsize);
                   ru->ru_idrss += pgtok(vm->vm_dsize);
                   ru->ru_isrss += pgtok(vm->vm_ssize);
                   rss = pgtok(vmspace_resident_count(vm));
                   if (ru->ru_maxrss < rss)
                           ru->ru_maxrss = rss;
           }
           mtx_unlock_spin_flags(&sched_lock, MTX_QUIET);
   }
   
   void
   profclock(frame)
           register struct clockframe *frame;
   {
           struct thread *td;
   #ifdef GPROF
           struct gmonparam *g;
           int i;
   #endif
   
           td = curthread;
           if (CLKF_USERMODE(frame)) {
                   /*
                    * Came from user mode; CPU was in user state.
                    * If this process is being profiled, record the tick.
                    * if there is no related user location yet, don't
                    * bother trying to count it.
                    */
                   td = curthread;
                   if (td->td_proc->p_flag & P_PROFIL)
                           addupc_intr(td, CLKF_PC(frame), 1);
           }
   #ifdef GPROF
           else {
                   /*
                    * Kernel statistics are just like addupc_intr, only easier.
                    */
                   g = &_gmonparam;
                   if (g->state == GMON_PROF_ON) {
                           i = CLKF_PC(frame) - g->lowpc;
                           if (i < g->textsize) {
                                   i /= HISTFRACTION * sizeof(*g->kcount);
                                   g->kcount[i]++;
                           }
                   }
           }
   #endif
   }
   
   /*
    * Return information about system clocks.
    */
   static int
   sysctl_kern_clockrate(SYSCTL_HANDLER_ARGS)
   {
           struct clockinfo clkinfo;
           /*
            * Construct clockinfo structure.
            */
           bzero(&clkinfo, sizeof(clkinfo));
           clkinfo.hz = hz;
           clkinfo.tick = tick;
           clkinfo.profhz = profhz;
           clkinfo.stathz = stathz ? stathz : hz;
           return (sysctl_handle_opaque(oidp, &clkinfo, sizeof clkinfo, req));
   }
   
   SYSCTL_PROC(_kern, KERN_CLOCKRATE, clockrate, CTLTYPE_STRUCT|CTLFLAG_RD,
           0, 0, sysctl_kern_clockrate, "S,clockinfo",
           "Rate and period of various kernel clocks");

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