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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 06/10] sched/fair: Clear the target CPU from the cpumask of CPUs searched
Date: Thu,  3 Dec 2020 14:11:20 +0000	[thread overview]
Message-ID: <20201203141124.7391-7-mgorman@techsingularity.net> (raw)
In-Reply-To: <20201203141124.7391-1-mgorman@techsingularity.net>

The target CPU is definitely not idle in both select_idle_core and
select_idle_cpu. For select_idle_core(), the SMT is potentially
checked unnecessarily as the core is definitely not idle if the
target is busy. For select_idle_cpu(), the first CPU checked is
simply a waste.

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
---
 kernel/sched/fair.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 68dd9cd62fbd..1d8f5c4b4936 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6077,6 +6077,7 @@ static int select_idle_core(struct task_struct *p, struct sched_domain *sd, int
 		return -1;
 
 	cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
+	__cpumask_clear_cpu(target, cpus);
 
 	for_each_cpu_wrap(core, cpus, target) {
 		bool idle = true;
@@ -6181,6 +6182,7 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t
 	time = cpu_clock(this);
 
 	cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
+	__cpumask_clear_cpu(target, cpus);
 
 	for_each_cpu_wrap(cpu, cpus, target) {
 		schedstat_inc(this_rq()->sis_scanned);
-- 
2.26.2


WARNING: multiple messages have this Message-ID (diff)
From: Mel Gorman <mgorman@techsingularity.net>
To: LKML <linux-kernel@vger.kernel.org>
Cc: Barry Song <song.bao.hua@hisilicon.com>,
	Juri Lelli <juri.lelli@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Peter Ziljstra <peterz@infradead.org>,
	Aubrey Li <aubrey.li@linux.intel.com>,
	Ingo Molnar <mingo@redhat.com>,
	Mel Gorman <mgorman@techsingularity.net>,
	Valentin Schneider <valentin.schneider@arm.com>,
	Linux-ARM <linux-arm-kernel@lists.infradead.org>
Subject: [PATCH 06/10] sched/fair: Clear the target CPU from the cpumask of CPUs searched
Date: Thu,  3 Dec 2020 14:11:20 +0000	[thread overview]
Message-ID: <20201203141124.7391-7-mgorman@techsingularity.net> (raw)
In-Reply-To: <20201203141124.7391-1-mgorman@techsingularity.net>

The target CPU is definitely not idle in both select_idle_core and
select_idle_cpu. For select_idle_core(), the SMT is potentially
checked unnecessarily as the core is definitely not idle if the
target is busy. For select_idle_cpu(), the first CPU checked is
simply a waste.

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
---
 kernel/sched/fair.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 68dd9cd62fbd..1d8f5c4b4936 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6077,6 +6077,7 @@ static int select_idle_core(struct task_struct *p, struct sched_domain *sd, int
 		return -1;
 
 	cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
+	__cpumask_clear_cpu(target, cpus);
 
 	for_each_cpu_wrap(core, cpus, target) {
 		bool idle = true;
@@ -6181,6 +6182,7 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t
 	time = cpu_clock(this);
 
 	cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
+	__cpumask_clear_cpu(target, cpus);
 
 	for_each_cpu_wrap(cpu, cpus, target) {
 		schedstat_inc(this_rq()->sis_scanned);
-- 
2.26.2


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

Thread overview: 60+ 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 ` Mel Gorman
2020-12-03 14:11 ` [PATCH 01/10] sched/fair: Track efficiency " Mel Gorman
2020-12-03 14:11   ` 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
2020-12-03 14:11 ` [PATCH 03/10] sched/fair: Remove SIS_AVG_CPU Mel Gorman
2020-12-03 14:11   ` Mel Gorman
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 14:11   ` Mel Gorman
2020-12-03 16:35   ` Vincent Guittot
2020-12-03 16:35     ` Vincent Guittot
2020-12-03 17:50     ` Mel Gorman
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   ` Mel Gorman
2020-12-03 14:11 ` Mel Gorman [this message]
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 16:38     ` Vincent Guittot
2020-12-03 17:52     ` Mel Gorman
2020-12-03 17:52       ` Mel Gorman
2020-12-04 10:56       ` Vincent Guittot
2020-12-04 10:56         ` Vincent Guittot
2020-12-04 11:30         ` Mel Gorman
2020-12-04 11:30           ` Mel Gorman
2020-12-04 13:13           ` Vincent Guittot
2020-12-04 13:13             ` Vincent Guittot
2020-12-04 13:17             ` Vincent Guittot
2020-12-04 13:17               ` Vincent Guittot
2020-12-04 13:40               ` Li, Aubrey
2020-12-04 13:40                 ` Li, Aubrey
2020-12-04 13:47                 ` Li, Aubrey
2020-12-04 13:47                   ` Li, Aubrey
2020-12-04 13:47                 ` Vincent Guittot
2020-12-04 13:47                   ` Vincent Guittot
2020-12-04 14:07                   ` Li, Aubrey
2020-12-04 14:07                     ` Li, Aubrey
2020-12-04 14:31                   ` Mel Gorman
2020-12-04 14:31                     ` Mel Gorman
2020-12-04 15:23                     ` Vincent Guittot
2020-12-04 15:23                       ` Vincent Guittot
2020-12-04 15:40                       ` Mel Gorman
2020-12-04 15:40                         ` Mel Gorman
2020-12-04 15:43                         ` Vincent Guittot
2020-12-04 15:43                           ` Vincent Guittot
2020-12-04 18:41                           ` Mel Gorman
2020-12-04 18:41                             ` Mel Gorman
2020-12-04 14:27               ` 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   ` 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   ` Mel Gorman
2020-12-03 14:11 ` [PATCH 09/10] sched/fair: Limit the search for an idle core Mel Gorman
2020-12-03 14:11   ` Mel Gorman
2020-12-03 14:19 ` 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
2020-12-03 14:20   ` Mel Gorman

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