On Mon, 7 Dec 2020 at 10:15, Mel Gorman <mgor...@techsingularity.net> wrote:
>
> SIS_AVG_CPU was introduced as a means of avoiding a search when the
> average search cost indicated that the search would likely fail. It
> was a blunt instrument and disabled by 4c77b18cf8b7 ("sched/fair: Make
> select_idle_cpu() more aggressive") and later replaced with a proportional
> search depth by 1ad3aaf3fcd2 ("sched/core: Implement new approach to
> scale select_idle_cpu()").
>
> While there are corner cases where SIS_AVG_CPU is better, it has now been
> disabled for almost three years. As the intent of SIS_PROP is to reduce
> the time complexity of select_idle_cpu(), lets drop SIS_AVG_CPU and focus
> on SIS_PROP as a throttling mechanism.
>
> Signed-off-by: Mel Gorman <mgor...@techsingularity.net>
Let see if someone complains but looks reasonable
> ---
> kernel/sched/fair.c | 3 ---
> kernel/sched/features.h | 1 -
> 2 files changed, 4 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 98075f9ea9a8..23934dbac635 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -6161,9 +6161,6 @@ static int select_idle_cpu(struct task_struct *p,
> struct sched_domain *sd, int t
> avg_idle = this_rq()->avg_idle / 512;
> avg_cost = this_sd->avg_scan_cost + 1;
>
> - if (sched_feat(SIS_AVG_CPU) && avg_idle < avg_cost)
> - return -1;
> -
> if (sched_feat(SIS_PROP)) {
> u64 span_avg = sd->span_weight * avg_idle;
> if (span_avg > 4*avg_cost)
> diff --git a/kernel/sched/features.h b/kernel/sched/features.h
> index 68d369cba9e4..e875eabb6600 100644
> --- a/kernel/sched/features.h
> +++ b/kernel/sched/features.h
> @@ -54,7 +54,6 @@ SCHED_FEAT(TTWU_QUEUE, true)
> /*
> * When doing wakeups, attempt to limit superfluous scans of the LLC domain.
> */
> -SCHED_FEAT(SIS_AVG_CPU, false)
> SCHED_FEAT(SIS_PROP, true)
>
> /*
> --
> 2.26.2
>
