4.4BSD/usr/src/sys/kern/kern_clock.c
/*-
* Copyright (c) 1982, 1986, 1991, 1993
* 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_clock.c 8.1 (Berkeley) 6/10/93
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/dkstat.h>
#include <sys/callout.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/resourcevar.h>
#include <machine/cpu.h>
#ifdef GPROF
#include <sys/gmon.h>
#endif
/*
* Clock handling routines.
*
* This code is written to operate with two timers that run independently of
* each other. The main clock, running hz times per second, is used to keep
* track of real time. 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.)
*/
/*
* TODO:
* allocate more timeout table slots when table overflows.
*/
/*
* Bump a timeval by a small number of usec's.
*/
#define BUMPTIME(t, usec) { \
register volatile struct timeval *tp = (t); \
register long us; \
\
tp->tv_usec = us = tp->tv_usec + (usec); \
if (us >= 1000000) { \
tp->tv_usec = us - 1000000; \
tp->tv_sec++; \
} \
}
int stathz;
int profhz;
int profprocs;
int ticks;
static int psdiv, pscnt; /* prof => stat divider */
int psratio; /* ratio: prof / stat */
volatile struct timeval time;
volatile struct timeval mono_time;
/*
* Initialize clock frequencies and start both clocks running.
*/
void
initclocks()
{
register int i;
/*
* Set divisors to 1 (normal case) and let the machine-specific
* code do its bit.
*/
psdiv = pscnt = 1;
cpu_initclocks();
/*
* Compute profhz/stathz, and fix profhz if needed.
*/
i = stathz ? stathz : hz;
if (profhz == 0)
profhz = i;
psratio = profhz / i;
}
/*
* The real-time timer, interrupting hz times per second.
*/
void
hardclock(frame)
register struct clockframe *frame;
{
register struct callout *p1;
register struct proc *p;
register int delta, needsoft;
extern int tickdelta;
extern long timedelta;
/*
* Update real-time timeout queue.
* At front of queue are some number of events which are ``due''.
* The time to these is <= 0 and if negative represents the
* number of ticks which have passed since it was supposed to happen.
* The rest of the q elements (times > 0) are events yet to happen,
* where the time for each is given as a delta from the previous.
* Decrementing just the first of these serves to decrement the time
* to all events.
*/
needsoft = 0;
for (p1 = calltodo.c_next; p1 != NULL; p1 = p1->c_next) {
if (--p1->c_time > 0)
break;
needsoft = 1;
if (p1->c_time == 0)
break;
}
p = curproc;
if (p) {
register struct pstats *pstats;
/*
* Run current process's virtual and profile time, as needed.
*/
pstats = p->p_stats;
if (CLKF_USERMODE(frame) &&
timerisset(&pstats->p_timer[ITIMER_VIRTUAL].it_value) &&
itimerdecr(&pstats->p_timer[ITIMER_VIRTUAL], tick) == 0)
psignal(p, SIGVTALRM);
if (timerisset(&pstats->p_timer[ITIMER_PROF].it_value) &&
itimerdecr(&pstats->p_timer[ITIMER_PROF], tick) == 0)
psignal(p, SIGPROF);
}
/*
* If no separate statistics clock is available, run it from here.
*/
if (stathz == 0)
statclock(frame);
/*
* Increment the time-of-day. The increment is just ``tick'' unless
* we are still adjusting the clock; see adjtime().
*/
ticks++;
if (timedelta == 0)
delta = tick;
else {
delta = tick + tickdelta;
timedelta -= tickdelta;
}
BUMPTIME(&time, delta);
BUMPTIME(&mono_time, delta);
/*
* Process callouts at a very low cpu priority, so we don't keep the
* relatively high clock interrupt priority any longer than necessary.
*/
if (needsoft) {
if (CLKF_BASEPRI(frame)) {
/*
* Save the overhead of a software interrupt;
* it will happen as soon as we return, so do it now.
*/
(void)splsoftclock();
softclock();
} else
setsoftclock();
}
}
/*
* Software (low priority) clock interrupt.
* Run periodic events from timeout queue.
*/
/*ARGSUSED*/
void
softclock()
{
register struct callout *c;
register void *arg;
register void (*func) __P((void *));
register int s;
s = splhigh();
while ((c = calltodo.c_next) != NULL && c->c_time <= 0) {
func = c->c_func;
arg = c->c_arg;
calltodo.c_next = c->c_next;
c->c_next = callfree;
callfree = c;
splx(s);
(*func)(arg);
(void) splhigh();
}
splx(s);
}
/*
* Arrange that (*func)(arg) is called in t/hz seconds.
*/
void
timeout(func, arg, t)
void (*func) __P((void *));
void *arg;
register int t;
{
register struct callout *p1, *p2, *pnew;
register int s;
s = splhigh();
if (t <= 0)
t = 1;
pnew = callfree;
if (pnew == NULL)
panic("timeout table overflow");
callfree = pnew->c_next;
pnew->c_arg = arg;
pnew->c_func = func;
for (p1 = &calltodo; (p2 = p1->c_next) && p2->c_time < t; p1 = p2)
if (p2->c_time > 0)
t -= p2->c_time;
p1->c_next = pnew;
pnew->c_next = p2;
pnew->c_time = t;
if (p2)
p2->c_time -= t;
splx(s);
}
/*
* untimeout is called to remove a function timeout call
* from the callout structure.
*/
void
untimeout(func, arg)
void (*func) __P((void *));
void *arg;
{
register struct callout *p1, *p2;
register int s;
s = splhigh();
for (p1 = &calltodo; (p2 = p1->c_next) != NULL; p1 = p2) {
if (p2->c_func == func && p2->c_arg == arg) {
if (p2->c_next && p2->c_time > 0)
p2->c_next->c_time += p2->c_time;
p1->c_next = p2->c_next;
p2->c_next = callfree;
callfree = p2;
break;
}
}
splx(s);
}
/*
* Compute number of hz until specified time.
* Used to compute third argument to timeout() from an
* absolute time.
*/
int
hzto(tv)
struct timeval *tv;
{
register long ticks, sec;
int s;
/*
* If number of milliseconds will fit in 32 bit arithmetic,
* then compute number of milliseconds to time and scale to
* ticks. Otherwise just compute number of hz in time, rounding
* times greater than representible to maximum value.
*
* Delta times less than 25 days can be computed ``exactly''.
* Maximum value for any timeout in 10ms ticks is 250 days.
*/
s = splhigh();
sec = tv->tv_sec - time.tv_sec;
if (sec <= 0x7fffffff / 1000 - 1000)
ticks = ((tv->tv_sec - time.tv_sec) * 1000 +
(tv->tv_usec - time.tv_usec) / 1000) / (tick / 1000);
else if (sec <= 0x7fffffff / hz)
ticks = sec * hz;
else
ticks = 0x7fffffff;
splx(s);
return (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;
{
int s;
if ((p->p_flag & SPROFIL) == 0) {
p->p_flag |= SPROFIL;
if (++profprocs == 1 && stathz != 0) {
s = splstatclock();
psdiv = pscnt = psratio;
setstatclockrate(profhz);
splx(s);
}
}
}
/*
* Stop profiling on a process.
*/
void
stopprofclock(p)
register struct proc *p;
{
int s;
if (p->p_flag & SPROFIL) {
p->p_flag &= ~SPROFIL;
if (--profprocs == 0 && stathz != 0) {
s = splstatclock();
psdiv = pscnt = 1;
setstatclockrate(stathz);
splx(s);
}
}
}
int dk_ndrive = DK_NDRIVE;
/*
* Statistics clock. Grab profile sample, and if divider reaches 0,
* do process and kernel statistics.
*/
void
statclock(frame)
register struct clockframe *frame;
{
#ifdef GPROF
register struct gmonparam *g;
#endif
register struct proc *p;
register int i;
if (CLKF_USERMODE(frame)) {
p = curproc;
if (p->p_flag & SPROFIL)
addupc_intr(p, CLKF_PC(frame), 1);
if (--pscnt > 0)
return;
/*
* Came from user mode; CPU was in user state.
* If this process is being profiled record the tick.
*/
p->p_uticks++;
if (p->p_nice > NZERO)
cp_time[CP_NICE]++;
else
cp_time[CP_USER]++;
} else {
#ifdef GPROF
/*
* 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
if (--pscnt > 0)
return;
/*
* 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.
*/
p = curproc;
if (CLKF_INTR(frame)) {
if (p != NULL)
p->p_iticks++;
cp_time[CP_INTR]++;
} else if (p != NULL) {
p->p_sticks++;
cp_time[CP_SYS]++;
} else
cp_time[CP_IDLE]++;
}
pscnt = psdiv;
/*
* We maintain statistics shown by user-level statistics
* programs: the amount of time in each cpu state, and
* the amount of time each of DK_NDRIVE ``drives'' is busy.
*
* XXX should either run linked list of drives, or (better)
* grab timestamps in the start & done code.
*/
for (i = 0; i < DK_NDRIVE; i++)
if (dk_busy & (1 << i))
dk_time[i]++;
/*
* We adjust the priority of the current process.
* The priority of a process gets worse as it accumulates
* CPU time. The cpu usage estimator (p_cpu) is increased here
* and the formula for computing priorities (in kern_synch.c)
* will compute a different value each time the p_cpu increases
* by 4. The cpu usage estimator ramps up quite quickly when
* the process is running (linearly), and decays away
* exponentially, at a rate which is proportionally slower
* when the system is busy. The basic principal is that the
* system will 90% forget that a process used a lot of CPU
* time in 5*loadav seconds. This causes the system to favor
* processes which haven't run much recently, and to
* round-robin among other processes.
*/
if (p != NULL) {
p->p_cpticks++;
if (++p->p_cpu == 0)
p->p_cpu--;
if ((p->p_cpu & 3) == 0) {
setpri(p);
if (p->p_pri >= PUSER)
p->p_pri = p->p_usrpri;
}
}
}
/*
* Return information about system clocks.
*/
sysctl_clockrate(where, sizep)
register char *where;
size_t *sizep;
{
struct clockinfo clkinfo;
/*
* Construct clockinfo structure.
*/
clkinfo.hz = hz;
clkinfo.tick = tick;
clkinfo.profhz = profhz;
clkinfo.stathz = stathz ? stathz : hz;
return (sysctl_rdstruct(where, sizep, NULL, &clkinfo, sizeof(clkinfo)));
}