From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751126AbcFAT71 (ORCPT ); Wed, 1 Jun 2016 15:59:27 -0400 Received: from merlin.infradead.org ([205.233.59.134]:50023 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750742AbcFAT70 (ORCPT ); Wed, 1 Jun 2016 15:59:26 -0400 Date: Wed, 1 Jun 2016 21:59:20 +0200 From: Peter Zijlstra To: Morten Rasmussen Cc: mingo@redhat.com, dietmar.eggemann@arm.com, yuyang.du@intel.com, vincent.guittot@linaro.org, mgalbraith@suse.de, linux-kernel@vger.kernel.org Subject: Re: [PATCH 04/16] sched/fair: Optimize find_idlest_cpu() when there is no choice Message-ID: <20160601195920.GE28447@twins.programming.kicks-ass.net> References: <1464001138-25063-1-git-send-email-morten.rasmussen@arm.com> <1464001138-25063-5-git-send-email-morten.rasmussen@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1464001138-25063-5-git-send-email-morten.rasmussen@arm.com> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 23, 2016 at 11:58:46AM +0100, Morten Rasmussen wrote: > 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)); > + } superfluous brackets, also isn't @this_cpu supposed to be part of the sched_group_cpu(group) mask?