From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753215AbeBLRa0 (ORCPT ); Mon, 12 Feb 2018 12:30:26 -0500 Received: from casper.infradead.org ([85.118.1.10]:47366 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751200AbeBLRaZ (ORCPT ); Mon, 12 Feb 2018 12:30:25 -0500 Date: Mon, 12 Feb 2018 18:29:26 +0100 From: Peter Zijlstra To: Mel Gorman Cc: Mike Galbraith , Matt Fleming , LKML Subject: Re: [PATCH 3/4] sched/fair: Do not migrate on wake_affine_weight if weights are equal Message-ID: <20180212172926.GY25201@hirez.programming.kicks-ass.net> References: <20180212145857.8056-1-mgorman@techsingularity.net> <20180212145857.8056-4-mgorman@techsingularity.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180212145857.8056-4-mgorman@techsingularity.net> User-Agent: Mutt/1.9.2 (2017-12-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Feb 12, 2018 at 02:58:56PM +0000, Mel Gorman wrote: > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index c1091cb023c4..28c8d9c91955 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -5747,7 +5747,16 @@ wake_affine_weight(struct sched_domain *sd, struct task_struct *p, > prev_eff_load *= 100 + (sd->imbalance_pct - 100) / 2; > prev_eff_load *= capacity_of(this_cpu); > > - return this_eff_load <= prev_eff_load ? this_cpu : nr_cpumask_bits; > + /* > + * If sync, adjust the weight of prev_eff_load such that if > + * prev_eff == this_eff that select_idle_sibling will consider > + * stacking the wakee on top of the waker if no other CPU is > + * idle. > + */ > + if (sync) > + prev_eff_load += 1; So where we had <= and would consistently favour pulling the task to the waking CPU when all else what equal, you now switch to <, such that when things are equal we do not pull. That makes sense I suppose. Except for sync wakeups, where you say, if everything else is equal, pull, which also makes sense, because sync says 'current' promises to go away. OK. > + > + return this_eff_load < prev_eff_load ? this_cpu : nr_cpumask_bits; > } > > static int wake_affine(struct sched_domain *sd, struct task_struct *p, > -- > 2.15.1 >