linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Mel Gorman <mgorman@techsingularity.net>
To: LKML <linux-kernel@vger.kernel.org>
Cc: 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>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Valentin Schneider <valentin.schneider@arm.com>,
	Linux-ARM <linux-arm-kernel@lists.infradead.org>,
	Mel Gorman <mgorman@techsingularity.net>
Subject: [PATCH 03/10] sched/fair: Remove SIS_AVG_CPU
Date: Thu,  3 Dec 2020 14:11:17 +0000	[thread overview]
Message-ID: <20201203141124.7391-4-mgorman@techsingularity.net> (raw)
In-Reply-To: <20201203141124.7391-1-mgorman@techsingularity.net>

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>
---
 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 d9acd55d309b..fc48cc99b03d 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6163,9 +6163,6 @@ 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


  parent reply	other threads:[~2020-12-03 14:12 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-03 14:11 [RFC PATCH 00/10] Reduce time complexity of select_idle_sibling Mel Gorman
2020-12-03 14:11 ` [PATCH 01/10] sched/fair: Track efficiency " Mel Gorman
2020-12-03 14:11 ` [PATCH 02/10] sched/fair: Track efficiency of task recent_used_cpu Mel Gorman
2020-12-03 14:11 ` Mel Gorman [this message]
2020-12-03 14:11 ` [PATCH 04/10] sched/fair: Return an idle cpu if one is found after a failed search for an idle core Mel Gorman
2020-12-03 16:35   ` Vincent Guittot
2020-12-03 17:50     ` Mel Gorman
2020-12-03 14:11 ` [PATCH 05/10] sched/fair: Do not replace recent_used_cpu with the new target Mel Gorman
2020-12-03 14:11 ` [PATCH 06/10] sched/fair: Clear the target CPU from the cpumask of CPUs searched Mel Gorman
2020-12-03 16:38   ` Vincent Guittot
2020-12-03 17:52     ` Mel Gorman
2020-12-04 10:56       ` Vincent Guittot
2020-12-04 11:30         ` Mel Gorman
2020-12-04 13:13           ` Vincent Guittot
2020-12-04 13:17             ` Vincent Guittot
2020-12-04 13:40               ` Li, Aubrey
2020-12-04 13:47                 ` Li, Aubrey
2020-12-04 13:47                 ` Vincent Guittot
2020-12-04 14:07                   ` Li, Aubrey
2020-12-04 14:31                   ` Mel Gorman
2020-12-04 15:23                     ` Vincent Guittot
2020-12-04 15:40                       ` Mel Gorman
2020-12-04 15:43                         ` Vincent Guittot
2020-12-04 18:41                           ` Mel Gorman
2020-12-04 14:27               ` Mel Gorman
2020-12-03 14:11 ` [PATCH 07/10] sched/fair: Account for the idle cpu/smt search cost Mel Gorman
2020-12-03 14:11 ` [PATCH 08/10] sched/fair: Reintroduce SIS_AVG_CPU but in the context of SIS_PROP to reduce search depth Mel Gorman
2020-12-03 14:11 ` [PATCH 09/10] sched/fair: Limit the search for an idle core Mel Gorman
2020-12-03 14:19 ` Mel Gorman
2020-12-03 14:20 ` [PATCH 10/10] sched/fair: Avoid revisiting CPUs multiple times during select_idle_sibling Mel Gorman

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20201203141124.7391-4-mgorman@techsingularity.net \
    --to=mgorman@techsingularity.net \
    --cc=aubrey.li@linux.intel.com \
    --cc=juri.lelli@redhat.com \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@redhat.com \
    --cc=peterz@infradead.org \
    --cc=song.bao.hua@hisilicon.com \
    --cc=valentin.schneider@arm.com \
    --cc=vincent.guittot@linaro.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).