From mboxrd@z Thu Jan 1 00:00:00 1970 From: Juri Lelli Subject: Re: [PATCH] Revert "cpufreq: schedutil: Don't restrict kthread to related_cpus unnecessarily" Date: Tue, 8 May 2018 14:17:35 +0200 Message-ID: <20180508121735.GD19168@localhost.localdomain> References: <20180508073340.13114-1-dietmar.eggemann@arm.com> <20180508082242.bre6sjfvefhz6xc3@vireshk-i7> <8cf21b1a-ca6e-fed7-43c5-94c66ff5986b@arm.com> <20180508094526.ajyjrwytguhv4xpe@vireshk-i7> <7922d081-0bfb-0e55-7caf-ec9fb5d7bab0@arm.com> <20180508105332.rxphnwo4byr42gmy@vireshk-i7> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20180508105332.rxphnwo4byr42gmy@vireshk-i7> Sender: linux-kernel-owner@vger.kernel.org To: Viresh Kumar Cc: Dietmar Eggemann , linux-kernel@vger.kernel.org, Peter Zijlstra , Ingo Molnar , linux-pm@vger.kernel.org, Pavan Kondeti , "Rafael J . Wysocki" , Joel Fernandes , Patrick Bellasi , Quentin Perret List-Id: linux-pm@vger.kernel.org On 08/05/18 16:23, Viresh Kumar wrote: > On 08-05-18, 12:36, Dietmar Eggemann wrote: > > That's true but where is the benefit by doing so? (Multiple) per-cluster or > > per-cpu frequency domains, why should the sugov kthread run on a foreign > > cpu? > > I am not sure I know the answer, but I have a question which you can > answer :) > > Is it possible for a CPU (which already has high priority deadline > activity going on) to be busy enough to be not able to run the > schedutil kthread for sometime ? That would be the only case I believe > where it would be better to let some other CPU go and change the > frequency for this one as we better run faster while we have the high > load going on. Shouldn't happen. This kthreads are "special" and will preempt any other DL task (stop class win of course).