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SubjectRe: [PATCH] sched/fair: Clear SMT siblings after determining the core is not idle
On Mon, 30 Nov 2020 at 15:40, Mel Gorman <mgorman@techsingularity.net> wrote:
>
> The clearing of SMT siblings from the SIS mask before checking for an idle
> core is a small but unnecessary cost. Defer the clearing of the siblings
> until the scan moves to the next potential target. The cost of this was
> not measured as it is borderline noise but it should be self-evident.

Good point

>
> Signed-off-by: Mel Gorman <mgorman@techsingularity.net>

Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>

> ---
> kernel/sched/fair.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 0d54d69ba1a5..d9acd55d309b 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -6087,10 +6087,11 @@ static int select_idle_core(struct task_struct *p, struct sched_domain *sd, int
> break;
> }
> }
> - cpumask_andnot(cpus, cpus, cpu_smt_mask(core));
>
> if (idle)
> return core;
> +
> + cpumask_andnot(cpus, cpus, cpu_smt_mask(core));
> }
>
> /*

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