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 289C1C43441 for ; Wed, 21 Nov 2018 16:05:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EB1C62174D for ; Wed, 21 Nov 2018 16:05:34 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EB1C62174D 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 S1731652AbeKVCkf (ORCPT ); Wed, 21 Nov 2018 21:40:35 -0500 Received: from foss.arm.com ([217.140.101.70]:53854 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730072AbeKVCke (ORCPT ); Wed, 21 Nov 2018 21:40:34 -0500 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 97E3F1D70; Wed, 21 Nov 2018 08:05:32 -0800 (PST) Received: from queper01-lin (queper01-lin.cambridge.arm.com [10.1.195.48]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 9F39E3F5CF; Wed, 21 Nov 2018 08:05:28 -0800 (PST) Date: Wed, 21 Nov 2018 16:05:27 +0000 From: Quentin Perret To: Peter Zijlstra Cc: rjw@rjwysocki.net, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, gregkh@linuxfoundation.org, mingo@redhat.com, dietmar.eggemann@arm.com, morten.rasmussen@arm.com, chris.redpath@arm.com, patrick.bellasi@arm.com, valentin.schneider@arm.com, vincent.guittot@linaro.org, thara.gopinath@linaro.org, viresh.kumar@linaro.org, tkjos@google.com, joel@joelfernandes.org, smuckle@google.com, adharmap@codeaurora.org, skannan@codeaurora.org, pkondeti@codeaurora.org, juri.lelli@redhat.com, edubezval@gmail.com, srinivas.pandruvada@linux.intel.com, currojerez@riseup.net, javi.merino@kernel.org Subject: Re: [PATCH v9 13/15] sched/fair: Introduce an energy estimation helper function Message-ID: <20181121160524.ulj6n3shb2fdwboj@queper01-lin> References: <20181119141857.8625-1-quentin.perret@arm.com> <20181119141857.8625-14-quentin.perret@arm.com> <20181121142803.GF2113@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181121142803.GF2113@hirez.programming.kicks-ass.net> User-Agent: NeoMutt/20171215 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wednesday 21 Nov 2018 at 15:28:03 (+0100), Peter Zijlstra wrote: > On Mon, Nov 19, 2018 at 02:18:55PM +0000, Quentin Perret wrote: > > +static long > > +compute_energy(struct task_struct *p, int dst_cpu, struct perf_domain *pd) > > +{ > > + long util, max_util, sum_util, energy = 0; > > + int cpu; > > + > > + for (; pd; pd = pd->next) { > > + max_util = sum_util = 0; > > + /* > > + * The capacity state of CPUs of the current rd can be driven by > > + * CPUs of another rd if they belong to the same performance > > + * domain. So, account for the utilization of these CPUs too > > + * by masking pd with cpu_online_mask instead of the rd span. > > + * > > + * If an entire performance domain is outside of the current rd, > > + * it will not appear in its pd list and will not be accounted > > + * by compute_energy(). > > + */ > > + for_each_cpu_and(cpu, perf_domain_span(pd), cpu_online_mask) { > > Should that not be cpu_active_mask ? Hmm, I must admit I'm sometimes a bit confused by the exact difference between these masks, so maybe yeah ... IIUC, cpu_active_mask is basically the set of CPUs on which the scheduler is actually allowed to migrate tasks. Is that correct ? I have always seen cpu_online_mask as a superset of cpu_active_mask which can also include CPUs which are still running 'special' tasks (kthreads and things like that I assume) although not allowed for migration any more (or not yet) because we're in the process of hotplugging that CPU. So, the thing is, I'm not trying to select a CPU candidate for my task here, I'm trying to understand what's the energy impact of a migration. That involves all CPUs that are running _something_ in a perf domain no matter if they're allowed to run more tasks or not. I mean, raising the OPP will make running online && !active CPUs more expensive as well. That's why I thought cpu_online_mask was good match here. Or maybe I'm confused again :-) > > > + util = cpu_util_next(cpu, p, dst_cpu); > > + util = schedutil_energy_util(cpu, util); > > + max_util = max(util, max_util); > > + sum_util += util; > > + } > > + > > + energy += em_pd_energy(pd->em_pd, max_util, sum_util); > > + } > > + > > + return energy; > > +} Thanks, Quentin