linux-kernel - [RFCv3 PATCH 46/48] sched: Turn off fast idling of cpus on a partially loaded system

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Message-Id: <1423074685-6336-47-git-send-email-morten.rasmussen@arm.com>
Date:	Wed,  4 Feb 2015 18:31:23 +0000
From:	Morten Rasmussen <morten.rasmussen@....com>
To:	peterz@...radead.org, mingo@...hat.com
Cc:	vincent.guittot@...aro.org, dietmar.eggemann@....com,
	yuyang.du@...el.com, preeti@...ux.vnet.ibm.com,
	mturquette@...aro.org, nico@...aro.org, rjw@...ysocki.net,
	juri.lelli@....com, linux-kernel@...r.kernel.org
Subject: [RFCv3 PATCH 46/48] sched: Turn off fast idling of cpus on a partially loaded system

From: Dietmar Eggemann <dietmar.eggemann@....com>

We do not want to miss out on the ability to do energy-aware idle load
balancing if the system is only partially loaded since the operational
range of energy-aware scheduling corresponds to a partially loaded
system. We might want to pull a single remaining task from a potential
src cpu towards an idle destination cpu if the energy model tells us
this is worth doing to save energy.

cc: Ingo Molnar <mingo@...hat.com>
cc: Peter Zijlstra <peterz@...radead.org>

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@....com>
---
 kernel/sched/fair.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index b6e2e92..92fd1d8 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7734,7 +7734,7 @@ static int idle_balance(struct rq *this_rq)
 	this_rq->idle_stamp = rq_clock(this_rq);
 
 	if (this_rq->avg_idle < sysctl_sched_migration_cost ||
-	    !this_rq->rd->overload) {
+	    (!energy_aware() && !this_rq->rd->overload)) {
 		rcu_read_lock();
 		sd = rcu_dereference_check_sched_domain(this_rq->sd);
 		if (sd)
-- 
1.9.1

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