From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934547AbaE2OEe (ORCPT ); Thu, 29 May 2014 10:04:34 -0400 Received: from casper.infradead.org ([85.118.1.10]:48018 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932751AbaE2OEc (ORCPT ); Thu, 29 May 2014 10:04:32 -0400 Date: Thu, 29 May 2014 16:04:27 +0200 From: Peter Zijlstra To: Vincent Guittot Cc: mingo@kernel.org, linux-kernel@vger.kernel.org, linux@arm.linux.org.uk, linux-arm-kernel@lists.infradead.org, preeti@linux.vnet.ibm.com, Morten.Rasmussen@arm.com, efault@gmx.de, nicolas.pitre@linaro.org, linaro-kernel@lists.linaro.org, daniel.lezcano@linaro.org Subject: Re: [PATCH v2 10/11] sched: move cfs task on a CPU with higher capacity Message-ID: <20140529140427.GI11074@laptop.programming.kicks-ass.net> References: <1400860385-14555-1-git-send-email-vincent.guittot@linaro.org> <1400860385-14555-11-git-send-email-vincent.guittot@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1400860385-14555-11-git-send-email-vincent.guittot@linaro.org> 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 Fri, May 23, 2014 at 05:53:04PM +0200, Vincent Guittot wrote: > @@ -7282,6 +7289,12 @@ static inline int nohz_kick_needed(struct rq *rq) > > if (nr_busy > 1) > goto need_kick_unlock; > + > + if ((rq->cfs.h_nr_running >= 1) > + && ((rq->cpu_power * sd->imbalance_pct) < > + (rq->cpu_power_orig * 100))) > + goto need_kick_unlock; > + > } > > sd = rcu_dereference(per_cpu(sd_asym, cpu)); So what happens when a cpu is consistently low on power (say due to a pinned RT task) the balancer would quickly adjust the load level, but this would endlessly kick things into action, even though we're balanced just fine.