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SubjectRe: [PATCH] sched/fair: Rearrange select_task_rq_fair() to optimize it
On 24-04-18, 11:02, Valentin Schneider wrote:
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index cacee15..ad09b67 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -6613,7 +6613,7 @@ static int wake_cap(struct task_struct *p, int cpu, int prev_cpu)
> static int
> select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags)
> {
> - struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
> + struct sched_domain *tmp, *sd = NULL;
> int cpu = smp_processor_id();
> int new_cpu = prev_cpu;
> int want_affine = 0;
> @@ -6636,8 +6636,10 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_f
> */
> if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
> cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
> + if (cpu != prev_cpu)
> + new_cpu = wake_affine(tmp, p, cpu, prev_cpu, sync);
> +
> sd = NULL; /* Prefer wake_affine over balance flags */
> - affine_sd = tmp;
> break;
> }
>
> @@ -6657,16 +6659,11 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_f
> sync_entity_load_avg(&p->se);
>
> new_cpu = find_idlest_cpu(sd, p, cpu, prev_cpu, sd_flag);
> - } else {
> - if (affine_sd && cpu != prev_cpu)
> - new_cpu = wake_affine(affine_sd, p, cpu, prev_cpu, sync);
> + } else if (sd_flag & SD_BALANCE_WAKE) { /* XXX always ? */
> + new_cpu = select_idle_sibling(p, prev_cpu, new_cpu);
>
> - if (sd_flag & SD_BALANCE_WAKE) { /* XXX always ? */
> - new_cpu = select_idle_sibling(p, prev_cpu, new_cpu);
> -
> - if (want_affine)
> - current->recent_used_cpu = cpu;
> - }
> + if (want_affine)
> + current->recent_used_cpu = cpu;
> }
> rcu_read_unlock();

LGTM.

I will merge it as part of the current patch, but maybe wait for a few
days before sending V2.

--
viresh

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