Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754227AbcKUMOK (ORCPT ); Mon, 21 Nov 2016 07:14:10 -0500 Received: from foss.arm.com ([217.140.101.70]:58504 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753347AbcKUMOI (ORCPT ); Mon, 21 Nov 2016 07:14:08 -0500 Date: Mon, 21 Nov 2016 12:14:32 +0000 From: Juri Lelli To: Peter Zijlstra Cc: Viresh Kumar , Rafael Wysocki , Ingo Molnar , linaro-kernel@lists.linaro.org, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, Vincent Guittot , Robin Randhawa , Steve Muckle , tkjos@google.com, Morten Rasmussen Subject: Re: [PATCH] cpufreq: schedutil: add up/down frequency transition rate limits Message-ID: <20161121121432.GK24383@e106622-lin> References: <20161121100805.GB10014@vireshk-i7> <20161121101946.GI3102@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161121101946.GI3102@twins.programming.kicks-ass.net> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1604 Lines: 41 On 21/11/16 11:19, Peter Zijlstra wrote: > On Mon, Nov 21, 2016 at 03:38:05PM +0530, Viresh Kumar wrote: > > On 17-11-16, 10:48, Viresh Kumar wrote: [...] > > > > (Background story for others from my discussion with Rafael on IRC: Rafael > > proposed that instead of this patch we can add down_rate_limit_delta_us (>0 =) > > which can be added to rate_limit_us (rate limit while increasing freq) to find > > the rate limit to be used in the downward direction. And I raised the point > > that it looks much neater to have separate up and down rate_limit_us. I also > > said that people may have a valid case where they want to keep down_rate_limit > > lower than up_rate_limit and Rafael wasn't fully sure of any such cases). > > > > Urgh... > > > So no tunables and rate limits here at all please. > > During LPC we discussed the rampup and decay issues and decided that we > should very much first address them by playing with the PELT stuff. > Morton was going to play with capping the decay on the util signal. This > should greatly improve the ramp-up scenario and cure some other wobbles. > > The decay can be set by changing the over-all pelt decay, if so desired. > Do you mean we might want to change the decay (make it different from ramp-up) once for all, or maybe we make it tunable so that we can address different power/perf requirements? > Also, there was the idea of; once the above ideas have all been > explored; tying the freq ram rate to the power curve. > Yep. That's an interesting one to look at, but it might require some time. > So NAK on everything tunable here.