Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965207AbcCPIFO (ORCPT ); Wed, 16 Mar 2016 04:05:14 -0400 Received: from casper.infradead.org ([85.118.1.10]:48106 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933246AbcCPIFF (ORCPT ); Wed, 16 Mar 2016 04:05:05 -0400 Date: Wed, 16 Mar 2016 09:05:03 +0100 From: Peter Zijlstra To: Steve Muckle Cc: Michael Turquette , rjw@rjwysocki.net, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, Juri.Lelli@arm.com, morten.rasmussen@arm.com, dietmar.eggemann@arm.com, vincent.guittot@linaro.org, Michael Turquette , Patrick Bellasi Subject: Re: [PATCH 4/8] cpufreq/schedutil: sysfs capacity margin tunable Message-ID: <20160316080503.GS6344@twins.programming.kicks-ass.net> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <56E8D4D9.1060202@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 Content-Length: 967 Lines: 20 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. The problem with starting out as ABI is that its hard to take away again.