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=-2.2 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 33D40C2BA83 for ; Fri, 14 Feb 2020 10:27:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 114AC20873 for ; Fri, 14 Feb 2020 10:27:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387441AbgBNK1C (ORCPT ); Fri, 14 Feb 2020 05:27:02 -0500 Received: from foss.arm.com ([217.140.110.172]:59472 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387424AbgBNK1B (ORCPT ); Fri, 14 Feb 2020 05:27:01 -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 2BD2B328; Fri, 14 Feb 2020 02:27:01 -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 477673F6CF; Fri, 14 Feb 2020 02:26:58 -0800 (PST) Subject: Re: [Patch v9 7/8] sched/fair: Enable tuning of decay period To: Thara Gopinath , Peter Zijlstra Cc: Randy Dunlap , mingo@redhat.com, ionela.voinescu@arm.com, vincent.guittot@linaro.org, rui.zhang@intel.com, qperret@google.com, daniel.lezcano@linaro.org, viresh.kumar@linaro.org, rostedt@goodmis.org, will@kernel.org, catalin.marinas@arm.com, sudeep.holla@arm.com, juri.lelli@redhat.com, corbet@lwn.net, linux-kernel@vger.kernel.org, amit.kachhap@gmail.com, javi.merino@kernel.org, amit.kucheria@verdurent.com References: <1580250967-4386-1-git-send-email-thara.gopinath@linaro.org> <1580250967-4386-8-git-send-email-thara.gopinath@linaro.org> <4eb10687-1a62-cee3-7285-3f50cc023071@infradead.org> <5E380D1D.7020500@linaro.org> <20200203155549.GL14914@hirez.programming.kicks-ass.net> <5E3DE7CC.3060300@linaro.org> <5E455533.3000600@linaro.org> From: Dietmar Eggemann Message-ID: <549ab3ab-f344-a915-7c6a-b0ffa808c354@arm.com> Date: Fri, 14 Feb 2020 11:26:56 +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: <5E455533.3000600@linaro.org> 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 13/02/2020 14:54, Thara Gopinath wrote: > On 02/10/2020 06:59 AM, Dietmar Eggemann wrote: >> On 07/02/2020 23:42, Thara Gopinath wrote: >>> On 02/04/2020 03:39 AM, Dietmar Eggemann wrote: >>>> On 03/02/2020 16:55, Peter Zijlstra wrote: >>>>> On Mon, Feb 03, 2020 at 07:07:57AM -0500, Thara Gopinath wrote: >>>>>> On 01/28/2020 06:56 PM, Randy Dunlap wrote: >>>>>>> Hi, >>>>>>> >>>>>>> On 1/28/20 2:36 PM, Thara Gopinath wrote: [...] >> is really not saying from which review comment the individual changes in >> the function name are coming from. And I don't see an answer to Ionela's >> email saying that her proposal will manifest in a particular part of >> this change. > Hi Dietmar, > > Like I said, don't want to argue on name. It is trivial for me. I have > v10 prepped with the name change. Will send it out shortly. Thanks. [...] >> Cpu-invariant accounting can't be guarded with a kernel CONFIG switch. >> Frequency-invariant accounting could be with CONFIG_CPU_FREQ but this is >> enabled by default by Arm64 defconfig. >> Thermal pressure (accounting) (CONFIG_HAVE_SCHED_THERMAL_PRESSURE) is >> disabled by default so why should a per-cpu thermal_pressure be >> maintained on such a system (CONFIG_CPU_THERMAL=y by default)? > > I agree that there is no need for per-cpu thermal pressure to be > maintained if no averaging is happening in the scheduler, today. I don't > know if there will ever be an use for it. All arch_scale_FOO() functions follow the approach to force the arch (currently x86, arm, arm64) to do #define arch_scale_FOO BAR to enable the FOO functionality. There is no direct link between consumer and provider here. consumer (sched) -> arch <- provider (arch, counters, CPUfreq, CPU cooling, etc.) So IMHO, FOO=thermal_pressure should follow this design pattern too. 'thermal_pressure' would be the only one which can be disabled by a kernel config switch at the consumer side. IMHO, it doesn't make sense to have the provider operating in this case. > My issue has to do with using a config option meant for internal > scheduler code being used else where. To me, once this happens, the > entire work done to separate out reading and writing of instantaneous > thermal pressure to arch_topology makes no sense. We could have kept it > in scheduler itself. You might see thermal_pressure more on the level of irq_load or [rt/dl]_rq_load and that could be why we have a different opinion here? Now rt_rq_load and dl_rq_load are scheduler internal providers and irq_load is driven by 'irq_delta + steal' time (which is much closer to the scheduler than thermal for instance). My assumption is that we don't want a direct link between the scheduler and e.g. a provider 'thermal'. > Another way I think about this whole thermal pressure framework is that > it is the job of cooling device or cpufreq or any other entity to update > a throttle in maximum pressure to the scheduler. It should be > independent of what scheduler does with it. Scheduler can choose to > ignore it