linux-kernel - [PATCH 1/2] sched: load_balance: Prevent reselect prev dst

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Date:	Sun, 15 Sep 2013 21:30:13 +0400
From:	Vladimir Davydov <vdavydov@...allels.com>
To:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>
CC:	Paul Turner <pjt@...gle.com>, <linux-kernel@...r.kernel.org>,
	<devel@...nvz.org>
Subject: [PATCH 1/2] sched: load_balance: Prevent reselect prev dst_cpu if some pinned

Currently new_dst_cpu is prevented from being reselected actually, not
dst_cpu. This can result in attempting to pull tasks to this_cpu twice.

Signed-off-by: Vladimir Davydov <vdavydov@...allels.com>
---
 kernel/sched/fair.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 9b3fe1c..cd59640 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5269,15 +5269,15 @@ more_balance:
 		 */
 		if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0) {
 
+			/* Prevent to re-select dst_cpu via env's cpus */
+			cpumask_clear_cpu(env.dst_cpu, env.cpus);
+
 			env.dst_rq	 = cpu_rq(env.new_dst_cpu);
 			env.dst_cpu	 = env.new_dst_cpu;
 			env.flags	&= ~LBF_SOME_PINNED;
 			env.loop	 = 0;
 			env.loop_break	 = sched_nr_migrate_break;
 
-			/* Prevent to re-select dst_cpu via env's cpus */
-			cpumask_clear_cpu(env.dst_cpu, env.cpus);
-
 			/*
 			 * Go back to "more_balance" rather than "redo" since we
 			 * need to continue with same src_cpu.
-- 
1.7.10.4

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