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SubjectRe: [PATCH 2/4] sched/fair: Move avg_scan_cost calculations under SIS_PROP
On Mon, 25 Jan 2021 at 09:59, Mel Gorman <mgorman@techsingularity.net> wrote:
>
> As noted by Vincent Guittot, avg_scan_costs are calculated for SIS_PROP
> even if SIS_PROP is disabled. Move the time calculations under a SIS_PROP
> check and while we are at it, exclude the cost of initialising the CPU
> mask from the average scan cost.
>
> Signed-off-by: Mel Gorman <mgorman@techsingularity.net>

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

> ---
> kernel/sched/fair.c | 14 ++++++++------
> 1 file changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 9f5682aeda2e..c8d8e185cf3b 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -6153,6 +6153,8 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t
> if (!this_sd)
> return -1;
>
> + cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
> +
> if (sched_feat(SIS_PROP)) {
> u64 avg_cost, avg_idle, span_avg;
>
> @@ -6168,11 +6170,9 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t
> nr = div_u64(span_avg, avg_cost);
> else
> nr = 4;
> - }
> -
> - time = cpu_clock(this);
>
> - cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
> + time = cpu_clock(this);
> + }
>
> for_each_cpu_wrap(cpu, cpus, target) {
> if (!--nr)
> @@ -6181,8 +6181,10 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t
> break;
> }
>
> - time = cpu_clock(this) - time;
> - update_avg(&this_sd->avg_scan_cost, time);
> + if (sched_feat(SIS_PROP)) {
> + time = cpu_clock(this) - time;
> + update_avg(&this_sd->avg_scan_cost, time);
> + }
>
> return cpu;
> }
> --
> 2.26.2
>

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