From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754583AbcEWLB6 (ORCPT ); Mon, 23 May 2016 07:01:58 -0400 Received: from foss.arm.com ([217.140.101.70]:50132 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754331AbcEWK6b (ORCPT ); Mon, 23 May 2016 06:58:31 -0400 From: Morten Rasmussen To: peterz@infradead.org, mingo@redhat.com Cc: dietmar.eggemann@arm.com, yuyang.du@intel.com, vincent.guittot@linaro.org, mgalbraith@suse.de, linux-kernel@vger.kernel.org, Morten Rasmussen Subject: [PATCH 04/16] sched/fair: Optimize find_idlest_cpu() when there is no choice Date: Mon, 23 May 2016 11:58:46 +0100 Message-Id: <1464001138-25063-5-git-send-email-morten.rasmussen@arm.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1464001138-25063-1-git-send-email-morten.rasmussen@arm.com> References: <1464001138-25063-1-git-send-email-morten.rasmussen@arm.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. cc: Ingo Molnar cc: Peter Zijlstra Signed-off-by: Morten Rasmussen --- kernel/sched/fair.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 0fe3020..564215d 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5155,6 +5155,11 @@ 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)) { -- 1.9.1