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[209.132.180.67]) by mx.google.com with ESMTP id v63-v6si3208215pgd.658.2018.07.27.01.10.05; Fri, 27 Jul 2018 01:10:19 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730088AbeG0J3w (ORCPT + 99 others); Fri, 27 Jul 2018 05:29:52 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:38666 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729430AbeG0J3w (ORCPT ); Fri, 27 Jul 2018 05:29:52 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 9552580D; Fri, 27 Jul 2018 01:09:08 -0700 (PDT) Received: from queper01-lin (queper01-lin.Emea.Arm.com [10.4.13.27]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A2C633F2EA; Fri, 27 Jul 2018 01:09:05 -0700 (PDT) Date: Fri, 27 Jul 2018 09:09:04 +0100 From: Quentin Perret To: Joel Fernandes Cc: Tejun Heo , Patrick Bellasi , linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, Ingo Molnar , Peter Zijlstra , "Rafael J . Wysocki" , Viresh Kumar , Vincent Guittot , Paul Turner , Dietmar Eggemann , Morten Rasmussen , Juri Lelli , Todd Kjos , Joel Fernandes , Steve Muckle , Suren Baghdasaryan Subject: Re: [PATCH v2 08/12] sched/core: uclamp: extend cpu's cgroup controller Message-ID: <20180727080827.u7tseookdhsckrec@queper01-lin> References: <20180716082906.6061-1-patrick.bellasi@arm.com> <20180716082906.6061-9-patrick.bellasi@arm.com> <20180723153040.GG1934745@devbig577.frc2.facebook.com> <20180723172215.GG2683@e110439-lin> <20180724132902.GI1934745@devbig577.frc2.facebook.com> <20180727003919.GA22416@joelaf.mtv.corp.google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180727003919.GA22416@joelaf.mtv.corp.google.com> User-Agent: NeoMutt/20171215 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thursday 26 Jul 2018 at 17:39:19 (-0700), Joel Fernandes wrote: > On Tue, Jul 24, 2018 at 06:29:02AM -0700, Tejun Heo wrote: > > Hello, Patrick. > > > > On Mon, Jul 23, 2018 at 06:22:15PM +0100, Patrick Bellasi wrote: > > > However, the "best effort" bandwidth control we have for CFS and RT > > > can be further improved if, instead of just looking at time spent on > > > CPUs, we provide some more hints to the scheduler to know at which > > > min/max "MIPS" we want to consume the (best effort) time we have been > > > allocated on a CPU. > > > > > > Such a simple extension is still quite useful to satisfy many use-case > > > we have, mainly on mobile systems, like the ones I've described in the > > > "Newcomer's Short Abstract (Updated)" > > > section of the cover letter: > > > https://lore.kernel.org/lkml/20180716082906.6061-1-patrick.bellasi@arm.com/T/#u > > > > So, that's all completely fine but then let's please not give it a > > name which doesn't quite match what it does. We can just call it > > e.g. cpufreq range control. > > But then what name can one give it if it does more than one thing, like > task-placement and CPU frequency control? > > It doesn't make sense to name it cpufreq IMHO. Its a clamp on the utilization > of the task which can be used for many purposes. Indeed, the scheduler could use clamped utilization values in several places. The capacity-awareness bits (mostly useful for big.LITTLE platforms) could already use that today I guess. And on the longer term, depending on where the EAS patches [1] end up, utilization clamping might actually become very useful to bias task placement decisions. EAS basically decides where to place tasks based on their utilization, so util_clamp would make a lot of sense there IMO. Thanks, Quentin [1] https://lkml.org/lkml/2018/7/24/420