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 EC4D5C2D0DB for ; Fri, 24 Jan 2020 15:37:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C9B662071E for ; Fri, 24 Jan 2020 15:37:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388539AbgAXPh2 (ORCPT ); Fri, 24 Jan 2020 10:37:28 -0500 Received: from foss.arm.com ([217.140.110.172]:53986 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388032AbgAXPh1 (ORCPT ); Fri, 24 Jan 2020 10:37:27 -0500 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 07D481FB; Fri, 24 Jan 2020 07:37:27 -0800 (PST) Received: from [192.168.0.7] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 16B0F3F6C4; Fri, 24 Jan 2020 07:37:24 -0800 (PST) Subject: Re: [Patch v8 4/7] sched/fair: Enable periodic update of average thermal pressure To: Vincent Guittot , Peter Zijlstra Cc: Thara Gopinath , Ingo Molnar , Ionela Voinescu , Zhang Rui , Quentin Perret , Daniel Lezcano , viresh kumar , linux-kernel , Amit Kachhap , Javi Merino , Amit Kucheria References: <1579031859-18692-1-git-send-email-thara.gopinath@linaro.org> <1579031859-18692-5-git-send-email-thara.gopinath@linaro.org> <20200116151502.GQ2827@hirez.programming.kicks-ass.net> <20200117145544.GE14879@hirez.programming.kicks-ass.net> From: Dietmar Eggemann Message-ID: Date: Fri, 24 Jan 2020 16:37:23 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 17/01/2020 16:39, Vincent Guittot wrote: > On Fri, 17 Jan 2020 at 15:55, Peter Zijlstra wrote: >> >> On Fri, Jan 17, 2020 at 02:22:51PM +0100, Vincent Guittot wrote: >>> On Thu, 16 Jan 2020 at 16:15, Peter Zijlstra wrote: >> >>>> >>>> That there indentation trainwreck is a reason to rename the function. >>>> >>>> decayed = update_rt_rq_load_avg(now, rq, curr_class == &rt_sched_class) | >>>> update_dl_rq_load_avg(now, rq, curr_class == &dl_sched_class) | >>>> update_thermal_load_avg(rq_clock_task(rq), rq, thermal_pressure) | >>>> update_irq_load_avg(rq, 0); >>>> >>>> Is much better. >>>> >>>> But now that you made me look at that, I noticed it's using a different >>>> clock -- it is _NOT_ using now/rq_clock_pelt(), which means it'll not be >>>> in sync with the other averages. >>>> >>>> Is there a good reason for that? >>> >>> We don't need to apply frequency and cpu capacity invariance on the >>> thermal capping signal which is what rq_clock_pelt does >> >> Hmm, I suppose that is true, and that really could've done with a >> comment. Now clock_pelt is sort-of in sync with clock_task, but won't it >> still give weird artifacts by having it on a slightly different basis? > > No we should not. Weird artifacts happens when we > add/subtract/propagate signals between each other and then apply pelt > algorithm on the results. In the case of thermal signal, we only add > it to others to update cpu_capacity but pelt algo is then not applied > on it. The error because of some signals being at segment boundaries > whereas others are not, is limited to 2% and doesn't accumulate over > time. > >> >> Anyway, looking at this, would it make sense to remove the @now argument >> from update_*_load_avg()? All those functions already take @rq, and >> rq_clock_*() are fairly trivial inlines. > > TBH I was thinking of doing the opposite for update_irq_load_avg which > hides the clock that is used for irq_avg. This helps to easily > identify which signals use the exact same clock and can be mixed to > create a new pelt signal and which can't The 'now' argument is one thing but why not: -int update_thermal_load_avg(u64 now, struct rq *rq, u64 capacity) +int update_thermal_load_avg(u64 now, struct rq *rq) { + u64 capacity = arch_cpu_thermal_pressure(cpu_of(rq)); + if (___update_load_sum(now, &rq->avg_thermal, This would make the call-sites __update_blocked_others() and task_tick(_fair)() cleaner. I guess the argument is not to pollute pelt.c. But it already contains arch_scale_[freq|cpu]_capacity() for irq.