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Do not IPI CPU that is already spinning for load. It doubles effect of

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spining (comparing to MWAIT) on some heavly switching test loads.
This commit is contained in:
Alexander Motin 2010-09-10 13:24:47 +00:00
parent acac60bbfe
commit 9f9ad565a1
1 changed files with 11 additions and 4 deletions
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15
sys/kern/sched_ule.c
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@ -196,7 +196,7 @@ static int preempt_thresh = 0;
#endif
static int static_boost = PRI_MIN_TIMESHARE;
static int sched_idlespins = 10000;
static int sched_idlespinthresh = 4;
static int sched_idlespinthresh = 64;
/*
* tdq - per processor runqs and statistics. All fields are protected by the
@ -208,6 +208,7 @@ struct tdq {
struct mtx tdq_lock; /* run queue lock. */
struct cpu_group *tdq_cg; /* Pointer to cpu topology. */
volatile int tdq_load; /* Aggregate load. */
volatile int tdq_cpu_idle; /* cpu_idle() is active. */
int tdq_sysload; /* For loadavg, !ITHD load. */
int tdq_transferable; /* Transferable thread count. */
short tdq_switchcnt; /* Switches this tick. */
@ -966,7 +967,7 @@ tdq_notify(struct tdq *tdq, struct thread *td)
* If the MD code has an idle wakeup routine try that before
* falling back to IPI.
*/
if (cpu_idle_wakeup(cpu))
if (!tdq->tdq_cpu_idle || cpu_idle_wakeup(cpu))
return;
}
tdq->tdq_ipipending = 1;
@ -2545,8 +2546,14 @@ sched_idletd(void *dummy)
}
}
switchcnt = tdq->tdq_switchcnt + tdq->tdq_oldswitchcnt;
if (tdq->tdq_load == 0)
cpu_idle(switchcnt > 1);
if (tdq->tdq_load == 0) {
tdq->tdq_cpu_idle = 1;
if (tdq->tdq_load == 0) {
cpu_idle(switchcnt > sched_idlespinthresh);
tdq->tdq_switchcnt++;
}
tdq->tdq_cpu_idle = 0;
}
if (tdq->tdq_load) {
thread_lock(td);
mi_switch(SW_VOL | SWT_IDLE, NULL);