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- Make runq_steal_from more aggressive. Previously it would examine only
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
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Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=262917
@ -1057,27 +1057,21 @@ runq_steal_from(struct runq *rq, int cpu, u_char start)
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struct rqhead *rqh;
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struct thread *td, *first;
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int bit;
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int pri;
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int i;
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rqb = &rq->rq_status;
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bit = start & (RQB_BPW -1);
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pri = 0;
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first = NULL;
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again:
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for (i = RQB_WORD(start); i < RQB_LEN; bit = 0, i++) {
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if (rqb->rqb_bits[i] == 0)
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continue;
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if (bit != 0) {
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for (pri = bit; pri < RQB_BPW; pri++)
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if (rqb->rqb_bits[i] & (1ul << pri))
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break;
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if (pri >= RQB_BPW)
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if (bit == 0)
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bit = RQB_FFS(rqb->rqb_bits[i]);
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for (; bit < RQB_BPW; bit++) {
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if ((rqb->rqb_bits[i] & (1ul << bit)) == 0)
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continue;
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} else
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pri = RQB_FFS(rqb->rqb_bits[i]);
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pri += (i << RQB_L2BPW);
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rqh = &rq->rq_queues[pri];
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rqh = &rq->rq_queues[bit + (i << RQB_L2BPW)];
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TAILQ_FOREACH(td, rqh, td_runq) {
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if (first && THREAD_CAN_MIGRATE(td) &&
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THREAD_CAN_SCHED(td, cpu))
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@ -1085,6 +1079,7 @@ runq_steal_from(struct runq *rq, int cpu, u_char start)
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first = td;
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}
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}
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}
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if (start != 0) {
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start = 0;
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goto again;
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