Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751111AbdCOXrK (ORCPT ); Wed, 15 Mar 2017 19:47:10 -0400 Received: from mail-ua0-f171.google.com ([209.85.217.171]:34080 "EHLO mail-ua0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750895AbdCOXqu (ORCPT ); Wed, 15 Mar 2017 19:46:50 -0400 MIME-Version: 1.0 In-Reply-To: <20170315162414.GI31499@e106622-lin> References: <1488292722-19410-1-git-send-email-patrick.bellasi@arm.com> <1488292722-19410-6-git-send-email-patrick.bellasi@arm.com> <20170315114052.GB18557@e110439-lin> <20170315144449.GH31499@e106622-lin> <20170315162414.GI31499@e106622-lin> From: Joel Fernandes Date: Wed, 15 Mar 2017 16:40:07 -0700 Message-ID: Subject: Re: [RFC v3 5/5] sched/{core,cpufreq_schedutil}: add capacity clamping for RT/DL tasks To: Juri Lelli Cc: Patrick Bellasi , "Joel Fernandes (Google)" , Linux Kernel Mailing List , linux-pm@vger.kernel.org, Ingo Molnar , Peter Zijlstra , "Rafael J . Wysocki" , Andres Oportus Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1178 Lines: 30 On Wed, Mar 15, 2017 at 9:24 AM, Juri Lelli wrote: [..] > >> > However, trying to quickly summarize how that would work (for who is >> > already somewhat familiar with reclaiming bits): >> > >> > - a task utilization contribution is accounted for (at rq level) as >> > soon as it wakes up for the first time in a new period >> > - its contribution is then removed after the 0lag time (or when the >> > task gets throttled) >> > - frequency transitions are triggered accordingly >> > >> > So, I don't see why triggering a go down request after the 0lag time >> > expired and quickly reacting to tasks waking up would have create >> > problems in your case? >> >> In my experience, the 'reacting to tasks' bit doesn't work very well. > > Humm.. but in this case we won't be 'reacting', we will be > 'anticipating' tasks' needs, right? Are you saying we will start ramping frequency before the next activation so that we're ready for it? If not, it sounds like it will only make the frequency request on the next activation when the Active bandwidth increases due to the task waking up. By then task has already started to run, right? Thanks, Joel