linux-kernel - [RFCv3 PATCH 45/48] sched: Skip cpu as lb src which has one task and capacity gte the dst cpu

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Message-Id: <1423074685-6336-46-git-send-email-morten.rasmussen@arm.com>
Date:	Wed,  4 Feb 2015 18:31:22 +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 45/48] sched: Skip cpu as lb src which has one task and capacity gte the dst cpu

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

Skip cpu as a potential src (costliest) in case it has only one task
running and its original capacity is greater than or equal to the
original capacity of the dst cpu.

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

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@....com>
---
 kernel/sched/fair.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 4849bad..b6e2e92 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7251,6 +7251,10 @@ static struct rq *find_busiest_queue(struct lb_env *env,
 			};
 			unsigned long energy = sched_group_energy(&eenv);
 
+			if (rq->nr_running == 1 && capacity_orig_of(i) >=
+					capacity_orig_of(env->dst_cpu))
+				continue;
+
 			/*
 			 * We're looking for the minimal cpu efficiency
 			 * min(u_i / e_i), crosswise multiplication leads to
-- 
1.9.1

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