From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michael Turquette Subject: Re: [PATCH 4/8] cpufreq/schedutil: sysfs capacity margin tunable Date: Wed, 16 Mar 2016 15:05:06 -0700 Message-ID: <20160316220506.11016.7525@quark.deferred.io> 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> <56E99E25.9070002@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8BIT Return-path: Received: from mail-pf0-f182.google.com ([209.85.192.182]:32854 "EHLO mail-pf0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965441AbcCPWFM convert rfc822-to-8bit (ORCPT ); Wed, 16 Mar 2016 18:05:12 -0400 Received: by mail-pf0-f182.google.com with SMTP id 124so91397835pfg.0 for ; Wed, 16 Mar 2016 15:05:12 -0700 (PDT) In-Reply-To: <56E99E25.9070002@linaro.org> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Steve Muckle , Juri Lelli , Peter Zijlstra Cc: 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 Quoting Steve Muckle (2016-03-16 10:55:49) > 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? It can. Let's keep the kernel interfaces in patch #2 for changing the margin/threshold, and schedtune can call these interfaces. Regards, Mike > > Regardless I agree that a debug interface is the way to go for now while > we figure things out. >