From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752768AbaHDRXr (ORCPT ); Mon, 4 Aug 2014 13:23:47 -0400 Received: from shelob.surriel.com ([74.92.59.67]:57984 "EHLO shelob.surriel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751180AbaHDRXn (ORCPT ); Mon, 4 Aug 2014 13:23:43 -0400 From: riel@redhat.com To: linux-kernel@vger.kernel.org Cc: peterz@infradead.org, mgorman@suse.de, mingo@kernel.org, vincent.guittot@linaro.org, Morten.Rasmussen@arm.com, nicolas.pitre@linaro.org, efault@gmx.de Subject: [PATCH 1/2] sched,numa: fix off-by-one in capacity check Date: Mon, 4 Aug 2014 13:23:27 -0400 Message-Id: <1407173008-9334-2-git-send-email-riel@redhat.com> X-Mailer: git-send-email 1.9.3 In-Reply-To: <1407173008-9334-1-git-send-email-riel@redhat.com> References: <1407173008-9334-1-git-send-email-riel@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Rik van Riel Commit a43455a1d572daf7b730fe12eb747d1e17411365 ensures that task_numa_migrate will call task_numa_compare on the preferred node all the time, even when the preferred node has no free capacity. This could lead to a performance regression if nr_running == capacity on both the source and the destination node. This can be avoided by also checking for nr_running == capacity on the source node, which is one stricter than checking .has_free_capacity. Signed-off-by: Rik van Riel --- 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 bfa3c86..678ed03 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1206,7 +1206,7 @@ static void task_numa_compare(struct task_numa_env *env, if (!cur) { /* Is there capacity at our destination? */ - if (env->src_stats.has_free_capacity && + if (env->src_stats.nr_running <= env->src_stats.task_capacity && !env->dst_stats.has_free_capacity) goto unlock; -- 1.9.3