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 A908DC606AF for ; Mon, 8 Jul 2019 11:09:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7E0832086D for ; Mon, 8 Jul 2019 11:09:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730358AbfGHLJJ (ORCPT ); Mon, 8 Jul 2019 07:09:09 -0400 Received: from foss.arm.com ([217.140.110.172]:44956 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727668AbfGHLJI (ORCPT ); Mon, 8 Jul 2019 07:09:08 -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 E06FE14F6; Mon, 8 Jul 2019 04:09:07 -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 A77353F738; Mon, 8 Jul 2019 04:09:06 -0700 (PDT) Date: Mon, 8 Jul 2019 12:09:04 +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: <20190708110904.ecrlr4p77n4r6qzk@e110439-lin> References: <20190627171603.14767-1-douglas.raillard@arm.com> <20190702155115.GW3436@hirez.programming.kicks-ass.net> <5198292b-1874-9ff4-6a9f-826a5ea00466@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5198292b-1874-9ff4-6a9f-826a5ea00466@arm.com> User-Agent: NeoMutt/20180716 Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org 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: [...] > > I'm not immediately seeing how it is transient; that is, PELT has a > > wobble in it's steady state, is that accounted for? > > > > The transient-ness of the ramp boost I'm introducing comes from the fact that for a > periodic task at steady state, task_ue.enqueued <= task_u when the task is executing. ^^^^^^^^^^^^^^^ I find your above "at steady state" a bit confusing. The condition "task_ue.enqueue <= task_u" is true only for the first task's big activation after a series of small activations, e.g. a task switching from 20% to 70%. That's the transient stat you refer to, isn't it? > That is because task_ue.enqueued is sampled at dequeue time, precisely at the moment > at which task_u is reaching its max for that task. Right, so in the example above we will have enqueued=20% while task_u is going above to converge towards 70% > Since we only take into account positive boosts, ramp boost will > only have an impact in the "increase transients". Right. I think Peter was referring to the smallish wobbles we see when the task already converged to 70%. If that's the case I would say they are already fully covered also by the current util_est. 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? Could you maybe come up with some experimental numbers related to that case specifically? Best, Patrick -- #include Patrick Bellasi