Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752655AbaFCRhx (ORCPT ); Tue, 3 Jun 2014 13:37:53 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:39012 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751290AbaFCRhw (ORCPT ); Tue, 3 Jun 2014 13:37:52 -0400 Date: Tue, 3 Jun 2014 19:37:41 +0200 From: Peter Zijlstra To: Morten Rasmussen Cc: Vincent Guittot , "mingo@kernel.org" , "linux-kernel@vger.kernel.org" , "linux@arm.linux.org.uk" , "linux-arm-kernel@lists.infradead.org" , "preeti@linux.vnet.ibm.com" , "efault@gmx.de" , "nicolas.pitre@linaro.org" , "linaro-kernel@lists.linaro.org" , "daniel.lezcano@linaro.org" , Paul Turner , Benjamin Segall Subject: Re: [PATCH v2 08/11] sched: get CPU's activity statistic Message-ID: <20140603173741.GE13930@laptop.programming.kicks-ass.net> References: <1400860385-14555-1-git-send-email-vincent.guittot@linaro.org> <1400860385-14555-9-git-send-email-vincent.guittot@linaro.org> <20140528121001.GI19967@e103034-lin> <20140603154058.GY30445@twins.programming.kicks-ass.net> <20140603171628.GE29593@e103034-lin> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140603171628.GE29593@e103034-lin> 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 Tue, Jun 03, 2014 at 06:16:28PM +0100, Morten Rasmussen wrote: > > I'm not too worried about the tipping point, per task runnable figures > > of an overloaded cpu are higher, so migration between an overloaded cpu > > and an underloaded cpu are going to be tricky no matter what we do. > > Yes, agreed. I just got the impression that you were concerned about > smp_nice last time we discussed this. Well, yes, we need to keep that working, but the exact detail around the tipping point are near impossible to get right, so I'm not too bothered there. > > > rq runnable_avg_sum is useful for decisions where we need a longer term > > > view of the cpu utilization, but I don't see how we can use as cpu > > > utilization metric for load-balancing decisions at wakeup or > > > periodically. > > > > So keeping one with a faster decay would add extra per-task storage. But > > would be possible.. > > I have had that thought when we discussed potential replacements for > cpu_load[]. It will require some messing around with the nicely > optimized load tracking maths if we want to have load tracking with a > different y-coefficient. My initial thought was a y=0.5, which is really >>=1. But yes, if we want something else that'll get messy real fast methinks. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/