From mboxrd@z Thu Jan 1 00:00:00 1970 From: Steve Muckle Subject: Re: [PATCH 4/8] cpufreq/schedutil: sysfs capacity margin tunable Date: Wed, 16 Mar 2016 10:55:49 -0700 Message-ID: <56E99E25.9070002@linaro.org> References: <1457932932-28444-1-git-send-email-mturquette+renesas@baylibre.com> <1457932932-28444-5-git-send-email-mturquette+renesas@baylibre.com> <20160315212047.GE6344@twins.programming.kicks-ass.net> <20160315214043.30639.75507@quark.deferred.io> <20160315214821.GM6344@twins.programming.kicks-ass.net> <20160315223701.30639.43127@quark.deferred.io> <56E8D4D9.1060202@linaro.org> <20160316080503.GS6344@twins.programming.kicks-ass.net> <20160316100257.GC18212@e106622-lin> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Return-path: Received: from mail-pf0-f172.google.com ([209.85.192.172]:34571 "EHLO mail-pf0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753659AbcCPRzu (ORCPT ); Wed, 16 Mar 2016 13:55:50 -0400 Received: by mail-pf0-f172.google.com with SMTP id x3so83657325pfb.1 for ; Wed, 16 Mar 2016 10:55:50 -0700 (PDT) In-Reply-To: <20160316100257.GC18212@e106622-lin> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Juri Lelli , Peter Zijlstra Cc: Michael Turquette , rjw@rjwysocki.net, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, morten.rasmussen@arm.com, dietmar.eggemann@arm.com, vincent.guittot@linaro.org, Michael Turquette , Patrick Bellasi On 03/16/2016 03:02 AM, Juri Lelli wrote: > Hi, > > On 16/03/16 09:05, Peter Zijlstra wrote: >> On Tue, Mar 15, 2016 at 08:36:57PM -0700, Steve Muckle wrote: >>>> Then again, maybe this knob will be part of the mythical >>>> power-vs-performance slider? >>> >>> Patrick Bellasi's schedtune series [0] (which I think is the referenced >>> mythical slider) aims to provide a more sophisticated interface for >>> tuning scheduler-driven frequency selection. In addition to a global >>> boost value it includes a cgroup controller as well for per-task tuning. >>> >>> I would definitely expect the margin/boost value to be modified at >>> runtime, for example if the battery is running low, or the user wants >>> 100% performance for a while, or the userspace framework wants to >>> temporarily tailor the performance level for a particular set of tasks, etc. >> >> OK, so how about we start with it as a debug knob, and once we have >> experience and feel like it is indeed a useful runtime knob, we upgrade >> it to ABI. >> > > I tend to agree here. To me the margin is something that we need to make > this thing work and to get acceptable performance out of the box. So we > can play with it while debugging, but I consider the schedtune slider as > the way to tune the system at runtime. Could the default schedtune value not serve as the out of the box margin? Regardless I agree that a debug interface is the way to go for now while we figure things out.