On 06/11/2015 10:35 PM, Mike Galbraith wrote:
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().
So maybe add a check in the if (sd_flag & SD_BALANCE_WAKE) for something
like this
if (tmp >= 0) {
new_cpu = tmp;
goto unlock;
} else if (!want_affine) {
new_cpu = prev_cpu;
}
so we can make sure we're not being pushed onto a cpu that we aren't
allowed on? Thanks,
Josef
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