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- Make runq_steal_from more aggressive. Previously it would examine only

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a single priority queue.  If that queue had a thread or threads which
   could not be migrated we would fail to steal load.  This could cause
   starvation in situations where cores are idle.

Submitted by:	Doug Kilpatrick <dkilpatrick@isilon.com>
Tested by:	pho
Reviewed by:	mav
Sponsored by:	EMC / Isilon Storage Division
This commit is contained in:
Jeff Roberson 2014-03-08 00:35:06 +00:00
parent 59c993d121
commit 8bc713f6c5
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=262917
1 changed files with 11 additions and 16 deletions
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27
sys/kern/sched_ule.c
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@ -1057,32 +1057,27 @@ runq_steal_from(struct runq *rq, int cpu, u_char start)
struct rqhead *rqh;
struct thread *td, *first;
int bit;
int pri;
int i;
rqb = &rq->rq_status;
bit = start & (RQB_BPW -1);
pri = 0;
first = NULL;
again:
for (i = RQB_WORD(start); i < RQB_LEN; bit = 0, i++) {
if (rqb->rqb_bits[i] == 0)
continue;
if (bit != 0) {
for (pri = bit; pri < RQB_BPW; pri++)
if (rqb->rqb_bits[i] & (1ul << pri))
break;
if (pri >= RQB_BPW)
if (bit == 0)
bit = RQB_FFS(rqb->rqb_bits[i]);
for (; bit < RQB_BPW; bit++) {
if ((rqb->rqb_bits[i] & (1ul << bit)) == 0)
continue;
} else
pri = RQB_FFS(rqb->rqb_bits[i]);
pri += (i << RQB_L2BPW);
rqh = &rq->rq_queues[pri];
TAILQ_FOREACH(td, rqh, td_runq) {
if (first && THREAD_CAN_MIGRATE(td) &&
THREAD_CAN_SCHED(td, cpu))
return (td);
first = td;
rqh = &rq->rq_queues[bit + (i << RQB_L2BPW)];
TAILQ_FOREACH(td, rqh, td_runq) {
if (first && THREAD_CAN_MIGRATE(td) &&
THREAD_CAN_SCHED(td, cpu))
return (td);
first = td;
}
}
}
if (start != 0) {