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 4F632C352A3 for ; Mon, 10 Feb 2020 12:00:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2FED92080C for ; Mon, 10 Feb 2020 12:00:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727436AbgBJMAD (ORCPT ); Mon, 10 Feb 2020 07:00:03 -0500 Received: from foss.arm.com ([217.140.110.172]:59292 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727347AbgBJMAD (ORCPT ); Mon, 10 Feb 2020 07:00:03 -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 6627E1FB; Mon, 10 Feb 2020 04:00:02 -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 7C3BF3F6CF; Mon, 10 Feb 2020 03:59:59 -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> From: Dietmar Eggemann Message-ID: Date: Mon, 10 Feb 2020 12:59:50 +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: <5E3DE7CC.3060300@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 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: [...] >> I do agree. IMHO, there are just two little things outstanding: >> >> (1) arch_scale_thermal_pressure() instead of >> arch_cpu_thermal_pressure() in v8 4/7 > > The "scale_" part was discussed in v6. Ionela had suggested that having > "scale" is not suited for this function because "thermal pressure" is > not exactly scaled but subtracted. I actually agree with that. > > https://lore.kernel.org/lkml/20191223175005.GA31446@arm.com/ > > Having said that if everyone feel the same about naming of this > function, I can change it one last time. I'm still in favor for this. And Vincent seems to be OK as well: https://lore.kernel.org/r/CAKfTPtBzoLnvAJ7sjPogMYS=WwBbdzWO07Kj=KDFVpO4=Su5ow@mail.gmail.com The 'v6->v7' change note: - Renamed arch_scale_thermal_capacity to arch_cpu_thermal_pressure as per review comments from Peter, Dietmar and Ionela. 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. >> (2) guarding of thermal pressure code in Arm's arch_topology driver w/ >> CONFIG_HAVE_SCHED_THERMAL_PRESSURE plus disabling it by default for >> Arm64. > It was enabled by default as per your suggestion in v9. > > The patch can be dropped. > > I don't understand the need to guard arch_topology with > CONFIG_HAVE_SCHED_THERMAL_PRESSURE. CONFIG_HAVE_SCHED_THERMAL_PRESSURE > is for scheduler to enable/disable averaging of thermal pressure. We > wanted to separate updating and retrieving of instantaneous thermal > pressure from scheduler. Guarding it with > CONFIG_HAVE_SCHED_THERMAL_PRESSURE is to me equivalent to putting back > this whole code in the scheduler framework. I am against it. I also do > not see other arch_ functions guarded similarly. 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)?