From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030373AbeE3Ihl (ORCPT ); Wed, 30 May 2018 04:37:41 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:52036 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030331AbeE3IhT (ORCPT ); Wed, 30 May 2018 04:37:19 -0400 Date: Wed, 30 May 2018 09:37:15 +0100 From: Quentin Perret To: Juri Lelli Cc: Vincent Guittot , peterz@infradead.org, mingo@kernel.org, linux-kernel@vger.kernel.org, rjw@rjwysocki.net, dietmar.eggemann@arm.com, Morten.Rasmussen@arm.com, viresh.kumar@linaro.org, valentin.schneider@arm.com Subject: Re: [PATCH v5 05/10] cpufreq/schedutil: get max utilization Message-ID: <20180530083715.GB2174@e108498-lin.cambridge.arm.com> References: <1527253951-22709-1-git-send-email-vincent.guittot@linaro.org> <1527253951-22709-6-git-send-email-vincent.guittot@linaro.org> <20180529084009.GE15173@e108498-lin.cambridge.arm.com> <20180529095203.GD8985@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180529095203.GD8985@localhost.localdomain> User-Agent: Mutt/1.8.3 (2017-05-23) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tuesday 29 May 2018 at 11:52:03 (+0200), Juri Lelli wrote: > On 29/05/18 09:40, Quentin Perret wrote: > > Hi Vincent, > > > > On Friday 25 May 2018 at 15:12:26 (+0200), Vincent Guittot wrote: > > > Now that we have both the dl class bandwidth requirement and the dl class > > > utilization, we can use the max of the 2 values when agregating the > > > utilization of the CPU. > > > > > > Signed-off-by: Vincent Guittot > > > --- > > > kernel/sched/sched.h | 6 +++++- > > > 1 file changed, 5 insertions(+), 1 deletion(-) > > > > > > diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h > > > index 4526ba6..0eb07a8 100644 > > > --- a/kernel/sched/sched.h > > > +++ b/kernel/sched/sched.h > > > @@ -2194,7 +2194,11 @@ static inline void cpufreq_update_util(struct rq *rq, unsigned int flags) {} > > > #ifdef CONFIG_CPU_FREQ_GOV_SCHEDUTIL > > > static inline unsigned long cpu_util_dl(struct rq *rq) > > > { > > > - return (rq->dl.running_bw * SCHED_CAPACITY_SCALE) >> BW_SHIFT; > > > + unsigned long util = (rq->dl.running_bw * SCHED_CAPACITY_SCALE) >> BW_SHIFT; > > > + > > > + util = max_t(unsigned long, util, READ_ONCE(rq->avg_dl.util_avg)); > > > > Would it make sense to use a UTIL_EST version of that signal here ? I > > don't think that would make sense for the RT class with your patch-set > > since you only really use the blocked part of the signal for RT IIUC, > > but would that work for DL ? > > Well, UTIL_EST for DL looks pretty much what we already do by computing > utilization based on dl.running_bw. That's why I was thinking of using > that as a starting point for dl.util_avg decay phase. Hmmm I see your point, but running_bw and the util_avg are fundamentally different ... I mean, the util_avg doesn't know about the period, which is an issue in itself I guess ... If you have a long running DL task (say 100ms runtime) with a long period (say 1s), the running_bw should represent ~1/10 of the CPU capacity, but the util_avg can go quite high, which means that you might end up executing this task at max OPP. So if we really want to drive OPPs like that for deadline, a util_est-like version of this util_avg signal should help. Now, you can also argue that going to max OPP for a task that _we know_ uses 1/10 of the CPU capacity isn't right ...