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SubjectRe: [PATCH v2 03/13] sched/fair: Optimize find_idlest_cpu() when there is no choice
On 22 June 2016 at 19:03, Morten Rasmussen <morten.rasmussen@arm.com> wrote:
> In the current find_idlest_group()/find_idlest_cpu() search we end up
> calling find_idlest_cpu() in a sched_group containing only one cpu in
> the end. Checking idle-states becomes pointless when there is no
> alternative, so bail out instead.
>
> cc: Ingo Molnar <mingo@redhat.com>
> cc: Peter Zijlstra <peterz@infradead.org>
>
> Signed-off-by: Morten Rasmussen <morten.rasmussen@arm.com>
> ---
> kernel/sched/fair.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index eec8e29104f9..216db302e87d 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -5123,6 +5123,10 @@ find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
> int shallowest_idle_cpu = -1;
> int i;
>
> + /* Check if we have any choice */
> + if (group->group_weight == 1)
> + return cpumask_first(sched_group_cpus(group));
> +
> /* Traverse only the allowed CPUs */
> for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
> if (idle_cpu(i)) {

FWIW, you can add my Acked-by: : Vincent Guittot <vincent.guittot@linaro.org>

> --
> 1.9.1
>

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