From: Vincent Guittot <vincent.guittot@linaro.org>
To: Mel Gorman <mgorman@techsingularity.net>
Cc: LKML <linux-kernel@vger.kernel.org>,
Aubrey Li <aubrey.li@linux.intel.com>,
Barry Song <song.bao.hua@hisilicon.com>,
Ingo Molnar <mingo@redhat.com>,
Peter Ziljstra <peterz@infradead.org>,
Juri Lelli <juri.lelli@redhat.com>,
Valentin Schneider <valentin.schneider@arm.com>,
Linux-ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH 1/4] sched/fair: Remove SIS_AVG_CPU
Date: Mon, 7 Dec 2020 16:05:50 +0100 [thread overview]
Message-ID: <CAKfTPtB8jOsFF9+cYVzRRLk+VskJBB_ZVNYdYC0P68Zow4k9bg@mail.gmail.com> (raw)
In-Reply-To: <20201207091516.24683-2-mgorman@techsingularity.net>
On Mon, 7 Dec 2020 at 10:15, Mel Gorman <mgorman@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 <mgorman@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
>
next prev parent reply other threads:[~2020-12-07 15:07 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-07 9:15 [RFC PATCH 0/4] Reduce worst-case scanning of runqueues in select_idle_sibling Mel Gorman
2020-12-07 9:15 ` [PATCH 1/4] sched/fair: Remove SIS_AVG_CPU Mel Gorman
2020-12-07 15:05 ` Vincent Guittot [this message]
2020-12-08 10:07 ` Dietmar Eggemann
2020-12-08 10:59 ` Mel Gorman
2020-12-08 13:24 ` Vincent Guittot
2020-12-08 13:36 ` Mel Gorman
2020-12-08 13:43 ` Vincent Guittot
2020-12-08 13:53 ` Mel Gorman
2020-12-08 14:47 ` Vincent Guittot
2020-12-08 15:12 ` Mel Gorman
2020-12-08 15:19 ` Vincent Guittot
2020-12-07 9:15 ` [PATCH 2/4] sched/fair: Do not replace recent_used_cpu with the new target Mel Gorman
2020-12-08 9:57 ` Dietmar Eggemann
2020-12-08 11:02 ` Mel Gorman
2020-12-07 9:15 ` [PATCH 3/4] sched/fair: Return an idle cpu if one is found after a failed search for an idle core Mel Gorman
2020-12-07 15:06 ` Vincent Guittot
2020-12-07 9:15 ` [PATCH 4/4] sched/fair: Avoid revisiting CPUs multiple times during select_idle_sibling Mel Gorman
2020-12-07 15:04 ` [RFC PATCH 0/4] Reduce worst-case scanning of runqueues in select_idle_sibling Vincent Guittot
2020-12-07 15:42 ` Mel Gorman
2020-12-08 2:06 ` Li, Aubrey
2020-12-08 15:34 [PATCH 0/4] Reduce " Mel Gorman
2020-12-08 15:34 ` [PATCH 1/4] sched/fair: Remove SIS_AVG_CPU Mel Gorman
2020-12-08 16:13 ` Vincent Guittot
2021-01-25 8:59 [PATCH v4 0/4] Scan for an idle sibling in a single pass Mel Gorman
2021-01-25 8:59 ` [PATCH 1/4] sched/fair: Remove SIS_AVG_CPU Mel Gorman
2021-01-27 13:51 [PATCH v5 0/4] Scan for an idle sibling in a single pass Mel Gorman
2021-01-27 13:52 ` [PATCH 1/4] sched/fair: Remove SIS_AVG_CPU Mel Gorman
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