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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