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From: tip-bot for Morten Rasmussen <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: tglx@linutronix.de, hpa@zytor.com, efault@gmx.de,
	torvalds@linux-foundation.org, peterz@infradead.org,
	morten.rasmussen@arm.com, mingo@kernel.org,
	linux-kernel@vger.kernel.org
Subject: [tip:sched/core] sched/fair: Optimize find_idlest_cpu() when there is no choice
Date: Wed, 10 Aug 2016 11:03:57 -0700	[thread overview]
Message-ID: <tip-eaecf41f5abf80b63c8e025fcb9ee4aa203c3038@git.kernel.org> (raw)
In-Reply-To: <1466615004-3503-4-git-send-email-morten.rasmussen@arm.com>

Commit-ID:  eaecf41f5abf80b63c8e025fcb9ee4aa203c3038
Gitweb:     http://git.kernel.org/tip/eaecf41f5abf80b63c8e025fcb9ee4aa203c3038
Author:     Morten Rasmussen <morten.rasmussen@arm.com>
AuthorDate: Wed, 22 Jun 2016 18:03:14 +0100
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 10 Aug 2016 14:03:32 +0200

sched/fair: Optimize find_idlest_cpu() when there is no choice

In the current find_idlest_group()/find_idlest_cpu() search we end up
calling find_idlest_cpu() in a sched_group containing only one CPU in
the end. Checking idle-states becomes pointless when there is no
alternative, so bail out instead.

Signed-off-by: Morten Rasmussen <morten.rasmussen@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dietmar.eggemann@arm.com
Cc: linux-kernel@vger.kernel.org
Cc: mgalbraith@suse.de
Cc: vincent.guittot@linaro.org
Cc: yuyang.du@intel.com
Link: http://lkml.kernel.org/r/1466615004-3503-4-git-send-email-morten.rasmussen@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 kernel/sched/fair.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index d819da6..acdc351 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5239,6 +5239,10 @@ find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
 	int shallowest_idle_cpu = -1;
 	int i;
 
+	/* Check if we have any choice: */
+	if (group->group_weight == 1)
+		return cpumask_first(sched_group_cpus(group));
+
 	/* Traverse only the allowed CPUs */
 	for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
 		if (idle_cpu(i)) {

  parent reply	other threads:[~2016-08-10 18:04 UTC|newest]

Thread overview: 64+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-22 17:03 [PATCH v2 00/13] sched: Clean-ups and asymmetric cpu capacity support Morten Rasmussen
2016-06-22 17:03 ` [PATCH v2 01/13] sched: Fix power to capacity renaming in comment Morten Rasmussen
2016-08-10 18:03   ` [tip:sched/core] sched/core: " tip-bot for Morten Rasmussen
2016-06-22 17:03 ` [PATCH v2 02/13] sched/fair: Consistent use of prev_cpu in wakeup path Morten Rasmussen
2016-06-22 18:04   ` Rik van Riel
2016-06-23  9:56     ` Morten Rasmussen
2016-06-23 12:24       ` Rik van Riel
2016-08-10 18:03   ` [tip:sched/core] sched/fair: Make the use of prev_cpu consistent in the " tip-bot for Morten Rasmussen
2016-06-22 17:03 ` [PATCH v2 03/13] sched/fair: Optimize find_idlest_cpu() when there is no choice Morten Rasmussen
2016-07-13 12:20   ` Vincent Guittot
2016-08-10 18:03   ` tip-bot for Morten Rasmussen [this message]
2016-06-22 17:03 ` [PATCH v2 04/13] sched: Introduce SD_ASYM_CPUCAPACITY sched_domain topology flag Morten Rasmussen
2016-07-11  9:55   ` Peter Zijlstra
2016-07-11 10:42     ` Morten Rasmussen
2016-06-22 17:03 ` [PATCH v2 05/13] sched: Enable SD_BALANCE_WAKE for asymmetric capacity systems Morten Rasmussen
2016-07-11 10:04   ` Peter Zijlstra
2016-07-11 10:37     ` Morten Rasmussen
2016-07-11 11:04       ` Morten Rasmussen
2016-07-11 11:24         ` Peter Zijlstra
2016-07-12 14:26           ` Morten Rasmussen
2016-06-22 17:03 ` [PATCH v2 06/13] sched: Store maximum per-cpu capacity in root domain Morten Rasmussen
2016-07-11 10:18   ` Peter Zijlstra
2016-07-11 16:16     ` Dietmar Eggemann
2016-07-12 11:42       ` Peter Zijlstra
2016-07-13 11:18         ` Dietmar Eggemann
2016-07-13 12:40   ` Vincent Guittot
2016-07-13 13:48     ` Dietmar Eggemann
2016-07-13 16:37       ` Morten Rasmussen
2016-07-14 13:25         ` Vincent Guittot
2016-07-14 15:15           ` Morten Rasmussen
2016-07-15 11:46             ` Morten Rasmussen
2016-07-15 13:39               ` Vincent Guittot
2016-07-15 16:02                 ` Morten Rasmussen
2016-07-18 12:48                   ` Vincent Guittot
2016-07-18 15:11                     ` Morten Rasmussen
2016-06-22 17:03 ` [PATCH v2 07/13] sched/fair: Let asymmetric cpu configurations balance at wake-up Morten Rasmussen
2016-07-11 11:13   ` Peter Zijlstra
2016-07-11 12:32     ` Morten Rasmussen
2016-07-13 12:56   ` Vincent Guittot
2016-07-13 16:14     ` Morten Rasmussen
2016-07-14 13:45       ` Vincent Guittot
2016-07-15  8:37         ` Morten Rasmussen
2016-06-22 17:03 ` [PATCH v2 08/13] sched/fair: Compute task/cpu utilization at wake-up more correctly Morten Rasmussen
2016-06-22 17:03 ` [PATCH v2 09/13] sched/fair: Consider spare capacity in find_idlest_group() Morten Rasmussen
2016-06-22 17:03 ` [PATCH v2 10/13] sched: Add per-cpu max capacity to sched_group_capacity Morten Rasmussen
2016-06-22 17:03 ` [PATCH v2 11/13] sched/fair: Avoid pulling tasks from non-overloaded higher capacity groups Morten Rasmussen
2016-06-23 21:20   ` Sai Gurrappadi
2016-06-30  7:49     ` Morten Rasmussen
2016-07-14 16:39       ` Sai Gurrappadi
2016-07-15  8:39         ` Morten Rasmussen
2016-07-12 12:59   ` Peter Zijlstra
2016-07-12 14:34     ` Morten Rasmussen
2016-06-22 17:03 ` [PATCH v2 12/13] arm: Set SD_ASYM_CPUCAPACITY for big.LITTLE platforms Morten Rasmussen
2016-06-22 17:03 ` [PATCH v2 13/13] arm: Update arch_scale_cpu_capacity() to reflect change to define Morten Rasmussen
2016-06-28 10:20 ` [PATCH v2 00/13] sched: Clean-ups and asymmetric cpu capacity support Koan-Sin Tan
2016-06-30  7:53   ` Morten Rasmussen
2016-07-08  7:35 ` KEITA KOBAYASHI
2016-07-08  8:18   ` Morten Rasmussen
2016-07-11  8:33 ` Morten Rasmussen
2016-07-11 12:44   ` Vincent Guittot
2016-07-12 13:25   ` Peter Zijlstra
2016-07-12 14:39     ` Morten Rasmussen
2016-07-13 12:06 ` Vincent Guittot
2016-07-13 15:54   ` Morten Rasmussen

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