Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757315AbdCUO7U (ORCPT ); Tue, 21 Mar 2017 10:59:20 -0400 Received: from merlin.infradead.org ([205.233.59.134]:57554 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756757AbdCUO7R (ORCPT ); Tue, 21 Mar 2017 10:59:17 -0400 Date: Tue, 21 Mar 2017 15:58:08 +0100 From: Peter Zijlstra To: Vincent Guittot Cc: "Rafael J. Wysocki" , Linux PM , LKML , Srinivas Pandruvada , Viresh Kumar , Juri Lelli , Patrick Bellasi , Joel Fernandes , Morten Rasmussen , Ingo Molnar Subject: Re: [RFC][PATCH v2 2/2] cpufreq: schedutil: Avoid decreasing frequency of busy CPUs Message-ID: <20170321145808.GS3093@worktop> References: <4366682.tsferJN35u@aspire.rjw.lan> <2185243.flNrap3qq1@aspire.rjw.lan> <3300960.HE4b3sK4dn@aspire.rjw.lan> <20170321132253.vjp7f72qkubpttmf@hirez.programming.kicks-ass.net> <20170321140325.gf64gc7eaqu335t5@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.22.1 (2013-10-16) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1025 Lines: 24 On Tue, Mar 21, 2017 at 03:16:19PM +0100, Vincent Guittot wrote: > On 21 March 2017 at 15:03, Peter Zijlstra wrote: > > > On Tue, Mar 21, 2017 at 02:37:08PM +0100, Vincent Guittot wrote: > > > On 21 March 2017 at 14:22, Peter Zijlstra wrote: > > > > > For the not overloaded case, it makes sense to immediately update to > > > OPP to be aligned with the new utilization of the CPU even if it was > > > not idle in the past couple of ticks > > > > Yeah, but we cannot know. Also, who cares? > > > > embedded system that doesn't want to stay at higest OPP if significant part > of the utilzation has moved away as an example > AFAICT, schedutil tries to select the best OPP according to the current > utilization of the CPU so if the utilization decreases, the OPP should also > decrease Sure I get that; but given the lack of crystal ball instructions we cannot know if this is the case or not. And if we really dropped below 100% utilization, we should hit idle fairly soon.