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make scheduler work better when a system has many runnable processes 

by making p_estcpu fixpt_t.  PR/31542.

1. schedcpu() decreases p_estcpu of all processes
   every seconds, by at least 1 regardless of load average.
2. schedclock() increases p_estcpu of curproc by 1,
   at about 16 hz.

in the consequence, if a system has >16 processes
with runnable lwps, their p_estcpu are not likely increased.

by making p_estcpu fixpt_t, we can decay it more slowly
when loadavg is high.  (ie. solve #1.)

i left kinfo_proc2::p_estcpu (ie. ps -O cpu) scaled because i have
no idea about its absolute value's usage other than debugging,
for which raw values are more valuable.
This commit is contained in:
yamt 2005-11-01 09:07:53 +00:00
parent b755c1973c
commit 8ab7495c2d
2 changed files with 37 additions and 17 deletions
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50
sys/kern/kern_synch.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: kern_synch.c,v 1.152 2005/10/30 20:28:56 yamt Exp $ */
/* $NetBSD: kern_synch.c,v 1.153 2005/11/01 09:07:53 yamt Exp $ */
/*-
* Copyright (c) 1999, 2000, 2004 The NetBSD Foundation, Inc.
@ -76,7 +76,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: kern_synch.c,v 1.152 2005/10/30 20:28:56 yamt Exp $");
__KERNEL_RCSID(0, "$NetBSD: kern_synch.c,v 1.153 2005/11/01 09:07:53 yamt Exp $");
#include "opt_ddb.h"
#include "opt_ktrace.h"
@ -169,6 +169,13 @@ roundrobin(struct cpu_info *ci)
need_resched(curcpu());
}
#define PPQ (128 / RUNQUE_NQS) /* priorities per queue */
#define NICE_WEIGHT 2 /* priorities per nice level */
#define ESTCPU_SHIFT 11
#define ESTCPU_MAX ((NICE_WEIGHT * PRIO_MAX - PPQ) << ESTCPU_SHIFT)
#define ESTCPULIM(e) min((e), ESTCPU_MAX)
/*
* Constants for digital decay and forget:
* 90% of (p_estcpu) usage in 5 * loadav time
@ -235,7 +242,25 @@ roundrobin(struct cpu_info *ci)
/* 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))
static fixpt_t
decay_cpu(fixpt_t loadfac, fixpt_t estcpu)
{
if (estcpu == 0) {
return 0;
}
#if !defined(_LP64)
/* avoid 64bit arithmetics. */
#define FIXPT_MAX ((fixpt_t)((UINTMAX_C(1) << sizeof(fixpt_t) * CHAR_BIT) - 1))
if (__predict_true(loadfac <= FIXPT_MAX / ESTCPU_MAX)) {
return estcpu * loadfac / (loadfac + FSCALE);
}
#endif /* !defined(_LP64) */
return (uint64_t)estcpu * loadfac / (loadfac + FSCALE);
}
/* decay 95% of `p_pctcpu' in 60 seconds; see CCPU_SHIFT before changing */
fixpt_t ccpu = 0.95122942450071400909 * FSCALE; /* exp(-1/20) */
@ -254,10 +279,6 @@ fixpt_t ccpu = 0.95122942450071400909 * FSCALE; /* exp(-1/20) */
*/
#define CCPU_SHIFT 11
#define PPQ (128 / RUNQUE_NQS) /* priorities per queue */
#define NICE_WEIGHT 2 /* priorities per nice level */
#define ESTCPULIM(e) min((e), NICE_WEIGHT * PRIO_MAX - PPQ)
/*
* Recompute process priorities, every hz ticks.
*/
@ -269,7 +290,6 @@ schedcpu(void *arg)
struct lwp *l;
struct proc *p;
int s, minslp;
unsigned int newcpu;
int clkhz;
proclist_lock_read();
@ -311,8 +331,7 @@ schedcpu(void *arg)
(p->p_cpticks * FSCALE / clkhz)) >> FSHIFT;
#endif
p->p_cpticks = 0;
newcpu = (u_int)decay_cpu(loadfac, p->p_estcpu);
p->p_estcpu = newcpu;
p->p_estcpu = decay_cpu(loadfac, p->p_estcpu);
splx(s); /* Done with the process CPU ticks update */
SCHED_LOCK(s);
LIST_FOREACH(l, &p->p_lwps, l_sibling) {
@ -341,13 +360,14 @@ schedcpu(void *arg)
/*
* Recalculate the priority of a process after it has slept for a while.
* For all load averages >= 1 and max p_estcpu of 255, sleeping for at
* least six times the loadfactor will decay p_estcpu to zero.
* least six times the loadfactor will decay p_estcpu to less than
* (1 << ESTCPU_SHIFT).
*/
void
updatepri(struct lwp *l)
{
struct proc *p = l->l_proc;
unsigned int newcpu;
fixpt_t newcpu;
fixpt_t loadfac;
SCHED_ASSERT_LOCKED();
@ -360,7 +380,7 @@ updatepri(struct lwp *l)
else {
l->l_slptime--; /* the first time was done in schedcpu */
while (newcpu && --l->l_slptime)
newcpu = (int) decay_cpu(loadfac, newcpu);
newcpu = decay_cpu(loadfac, newcpu);
p->p_estcpu = newcpu;
}
resetpriority(l);
@ -1119,7 +1139,7 @@ resetpriority(struct lwp *l)
SCHED_ASSERT_LOCKED();
newpriority = PUSER + p->p_estcpu +
newpriority = PUSER + (p->p_estcpu >> ESTCPU_SHIFT) +
NICE_WEIGHT * (p->p_nice - NZERO);
newpriority = min(newpriority, MAXPRI);
l->l_usrpri = newpriority;
@ -1159,7 +1179,7 @@ schedclock(struct lwp *l)
struct proc *p = l->l_proc;
int s;
p->p_estcpu = ESTCPULIM(p->p_estcpu + 1);
p->p_estcpu = ESTCPULIM(p->p_estcpu + (1 << ESTCPU_SHIFT));
SCHED_LOCK(s);
resetpriority(l);
SCHED_UNLOCK(s);

4
sys/sys/proc.h
View File

@ -1,4 +1,4 @@
/* $NetBSD: proc.h,v 1.206 2005/08/28 14:57:18 yamt Exp $ */
/* $NetBSD: proc.h,v 1.207 2005/11/01 09:07:53 yamt Exp $ */
/*-
* Copyright (c) 1986, 1989, 1991, 1993
@ -201,7 +201,7 @@ struct proc {
struct sadata *p_sa; /* Scheduler activation information */
/* scheduling */
u_int p_estcpu; /* Time averaged value of p_cpticks XXX belongs in p_startcopy section */
fixpt_t p_estcpu; /* Time averaged value of p_cpticks XXX belongs in p_startcopy section */
int p_cpticks; /* Ticks of CPU time */
fixpt_t p_pctcpu; /* %cpu for this process during p_swtime */