From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1A9A6C43142 for ; Fri, 22 Jun 2018 15:30:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C8E33244D0 for ; Fri, 22 Jun 2018 15:30:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C8E33244D0 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933849AbeFVPaZ (ORCPT ); Fri, 22 Jun 2018 11:30:25 -0400 Received: from foss.arm.com ([217.140.101.70]:36946 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933304AbeFVPaY (ORCPT ); Fri, 22 Jun 2018 11:30:24 -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 6DE6780D; Fri, 22 Jun 2018 08:30:24 -0700 (PDT) Received: from e108498-lin.cambridge.arm.com (e108498-lin.cambridge.arm.com [10.1.211.46]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 1432F3F557; Fri, 22 Jun 2018 08:30:21 -0700 (PDT) Date: Fri, 22 Jun 2018 16:30:17 +0100 From: Quentin Perret To: Peter Zijlstra Cc: Vincent Guittot , mingo@kernel.org, linux-kernel@vger.kernel.org, rjw@rjwysocki.net, juri.lelli@redhat.com, dietmar.eggemann@arm.com, Morten.Rasmussen@arm.com, viresh.kumar@linaro.org, valentin.schneider@arm.com, patrick.bellasi@arm.com, joel@joelfernandes.org, daniel.lezcano@linaro.org, Ingo Molnar Subject: Re: [PATCH v6 04/11] cpufreq/schedutil: use rt utilization tracking Message-ID: <20180622153016.GA29031@e108498-lin.cambridge.arm.com> References: <1528459794-13066-1-git-send-email-vincent.guittot@linaro.org> <1528459794-13066-5-git-send-email-vincent.guittot@linaro.org> <20180621184524.GB27616@hirez.programming.kicks-ass.net> <20180622075853.GC23168@e108498-lin.cambridge.arm.com> <20180622113713.GJ2494@hirez.programming.kicks-ass.net> <20180622152258.GF2512@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180622152258.GF2512@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.8.3 (2017-05-23) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Friday 22 Jun 2018 at 17:22:58 (+0200), Peter Zijlstra wrote: > On Fri, Jun 22, 2018 at 01:37:13PM +0200, Peter Zijlstra wrote: > > That is true.. So we could limit the scaling to the case where there is > > no idle time, something like: > > > > util = sg_cpu->util_cfs; > > > > cap_cfs = (1024 - (sg_cpu->util_rt + ...)); > > if (util == cap_cfs) > > util = sg_cpu->max; > > > > OK, it appears this is more or less what the patches do. And I think > there's a small risk/hole with this where util ~= cap_cfs but very close > due to some unaccounted time. So Vincent suggested at some point to add a margin to avoid that issue IIRC. FWIW, this is what the overutilized flag of EAS does. It basically says, if there isn't enough idle time in the system (cfs_util is too close to cap_cfs), don't bother looking at the util signals because they'll be kinda wrong. So what about something like, go to max freq if overutilized ? Or something similar on a per cpufreq policy basis ? Thanks, Quentin