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_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 A2044C606B0 for ; Tue, 9 Jul 2019 10:38:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7DCB820844 for ; Tue, 9 Jul 2019 10:38:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726108AbfGIKiR (ORCPT ); Tue, 9 Jul 2019 06:38:17 -0400 Received: from foss.arm.com ([217.140.110.172]:41194 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725947AbfGIKiQ (ORCPT ); Tue, 9 Jul 2019 06:38:16 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id EFEF92B; Tue, 9 Jul 2019 03:38:15 -0700 (PDT) Received: from e110439-lin (e110439-lin.cambridge.arm.com [10.1.194.43]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id B60603F738; Tue, 9 Jul 2019 03:38:14 -0700 (PDT) Date: Tue, 9 Jul 2019 11:37:50 +0100 From: Patrick Bellasi To: Douglas Raillard Cc: Peter Zijlstra , linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, mingo@redhat.com, rjw@rjwysocki.net, viresh.kumar@linaro.org, quentin.perret@arm.com, dietmar.eggemann@arm.com Subject: Re: [RFC PATCH v2 0/5] sched/cpufreq: Make schedutil energy aware Message-ID: <20190709103750.hnm4bav6tjy7g37u@e110439-lin> References: <20190627171603.14767-1-douglas.raillard@arm.com> <20190702155115.GW3436@hirez.programming.kicks-ass.net> <5198292b-1874-9ff4-6a9f-826a5ea00466@arm.com> <20190708110904.ecrlr4p77n4r6qzk@e110439-lin> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20180716 Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org On 08-Jul 14:46, Douglas Raillard wrote: > Hi Patrick, > > On 7/8/19 12:09 PM, Patrick Bellasi wrote: > > On 03-Jul 17:36, Douglas Raillard wrote: > > > On 7/2/19 4:51 PM, Peter Zijlstra wrote: > > > > On Thu, Jun 27, 2019 at 06:15:58PM +0100, Douglas RAILLARD wrote: [...] > > You are also correct in pointing out that in the steady state > > ramp_boost will not be triggered in that steady state. > > > > IMU, that's for two main reasons: > > a) it's very likely that enqueued <= util_avg > > b) even in case enqueued should turn out to be _slightly_ bigger then > > util_avg, the corresponding (proportional) ramp_boost would be so > > tiny to not have any noticeable effect on OPP selection. > > > > Am I correct on point b) above? > > Assuming you meant "util_avg slightly bigger than enqueued" (which is when boosting triggers), > then yes since ramp_boost effect is proportional to "task_ue.enqueue - task_u". It makes it robust > against that. Right :) > > Could you maybe come up with some experimental numbers related to that > > case specifically? > > With: > * an rt-app task ramping up from 5% to 75% util in one big step. The > whole cycle is 0.6s long (0.3s at 5% followed by 0.3s at 75%). This > cycle is repeated 20 times and the average of boosting is taken. > > * a hikey 960 (this impact the frequency at which the test runs at > the beginning of 75% phase, which impacts the number of missed > activations before the util ramped up). > > * assuming an OPP exists for each util value (i.e. 1024 OPPs, so the > effect of boost on consumption is not impacted by OPP capacities > granularity) > > Then the boosting feature would increase the average power > consumption by 3.1%, out of which 0.12% can be considered "spurious > boosting" due to the util taking some time to really converge to its > steady state value. > > In practice, the impact of small boosts will be even lower since > they will less likely trigger the selection of a high OPP due to OPP > capacity granularity > 1 util unit. That's ok for the energy side: you estimate a ~3% worst case more energy on that specific target. By boosting I expect the negative boost to improve. Do you have also numbers/stats related to the negative slack? Can you share a percentage figure for that improvement? Best, Patrick -- #include Patrick Bellasi