Messages in this thread | | | Subject | Re: [PATCH RESEND] sched: prefer an idle cpu vs an idle sibling for BALANCE_WAKE | From | Mike Galbraith <> | Date | Fri, 12 Jun 2015 07:35:05 +0200 |
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On Thu, 2015-05-28 at 13:05 +0200, Peter Zijlstra wrote:
> @@ -5022,22 +5026,28 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_f > * If both cpu and prev_cpu are part of this domain, > * cpu is a valid SD_WAKE_AFFINE target. > */ > - if (want_affine && (tmp->flags & SD_WAKE_AFFINE) && > - cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) { > + if (want_affine && !affine_sd && > + (tmp->flags & SD_WAKE_AFFINE) && > + cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) > affine_sd = tmp; > - break; > - } > > if (tmp->flags & sd_flag) > sd = tmp; > + else if (!want_affine || (want_affine && affine_sd)) > + break; > }
Hm, new_cpu == cpu.
> - if (affine_sd && cpu != prev_cpu && wake_affine(affine_sd, p, sync)) > + if (affine_sd && cpu != prev_cpu && wake_affine(affine_sd, p, sync)) { > prev_cpu = cpu; > + sd = NULL; /* WAKE_AFFINE trumps BALANCE_WAKE */ > + }
If branch above is not taken, new_cpu remains cpu.
> if (sd_flag & SD_BALANCE_WAKE) { > - new_cpu = select_idle_sibling(p, prev_cpu); > - goto unlock; > + int tmp = select_idle_sibling(p, prev_cpu); > + if (tmp >= 0) { > + new_cpu = tmp; > + goto unlock; > + } > }
If select_idle_sibling() returns -1, new_cpu remains cpu.
> > while (sd) {
If sd == NULL, we fall through and try to pull wakee despite nacked-by tsk_cpus_allowed() or wake_affine().
-Mike
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