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=-3.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_NEOMUTT 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 A073DC46471 for ; Tue, 7 Aug 2018 13:54:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4EC7B2178F for ; Tue, 7 Aug 2018 13:54:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4EC7B2178F 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 S2389333AbeHGQIi (ORCPT ); Tue, 7 Aug 2018 12:08:38 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:54718 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727605AbeHGQIi (ORCPT ); Tue, 7 Aug 2018 12:08:38 -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 ACCE97A9; Tue, 7 Aug 2018 06:54:11 -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 DE5863F5B3; Tue, 7 Aug 2018 06:54:08 -0700 (PDT) Date: Tue, 7 Aug 2018 14:54:04 +0100 From: Quentin Perret To: Patrick Bellasi Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, Ingo Molnar , Peter Zijlstra , Tejun Heo , "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 v3 06/14] sched/cpufreq: uclamp: add utilization clamping for RT tasks Message-ID: <20180807135403.s7jktvxmhycujeht@queper01-lin> References: <20180806163946.28380-1-patrick.bellasi@arm.com> <20180806163946.28380-7-patrick.bellasi@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180806163946.28380-7-patrick.bellasi@arm.com> User-Agent: NeoMutt/20171215 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Patrick, On Monday 06 Aug 2018 at 17:39:38 (+0100), Patrick Bellasi wrote: > diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c > index a7affc729c25..bb25ef66c2d3 100644 > --- a/kernel/sched/cpufreq_schedutil.c > +++ b/kernel/sched/cpufreq_schedutil.c > @@ -200,6 +200,7 @@ static unsigned int get_next_freq(struct sugov_policy *sg_policy, > static unsigned long sugov_get_util(struct sugov_cpu *sg_cpu) > { > struct rq *rq = cpu_rq(sg_cpu->cpu); > + unsigned long util_cfs, util_rt; > unsigned long util, irq, max; > > sg_cpu->max = max = arch_scale_cpu_capacity(NULL, sg_cpu->cpu); IIUC, not far below this you should still have something like: if (rt_rq_is_runnable(&rq->rt)) return max; So you won't reach the actual clamping code at the end of the function when a RT task is runnable no? Also, I always had the feeling that the default for RT should be util_min == 1024, and then users could decide to lower the bar if they want to. For the specific case of RT, that feels more natural than applying a max util clamp IMO. What do you think ? Thanks, Quentin