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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,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 595C5C6379D for ; Tue, 17 Nov 2020 10:45:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 106EB238E6 for ; Tue, 17 Nov 2020 10:45:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727879AbgKQKpq (ORCPT ); Tue, 17 Nov 2020 05:45:46 -0500 Received: from foss.arm.com ([217.140.110.172]:53792 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727272AbgKQKpp (ORCPT ); Tue, 17 Nov 2020 05:45:45 -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 567D2D6E; Tue, 17 Nov 2020 02:45:44 -0800 (PST) Received: from [10.57.54.66] (unknown [10.57.54.66]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 14D333F718; Tue, 17 Nov 2020 02:45:41 -0800 (PST) Subject: Re: [PATCH v3 3/3] [RFC] CPUFreq: Add support for cpu-perf-dependencies To: Viresh Kumar , Lukasz Luba Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-pm@vger.kernel.org, devicetree@vger.kernel.org, sudeep.holla@arm.com, rjw@rjwysocki.net, vireshk@kernel.org, robh+dt@kernel.org, sboyd@kernel.org, nm@ti.com, daniel.lezcano@linaro.org, morten.rasmussen@arm.com, chris.redpath@arm.com References: <20201102120115.29993-1-nicola.mazzucato@arm.com> <20201102120115.29993-4-nicola.mazzucato@arm.com> <20201106092020.za3oxg7gutzc3y2b@vireshk-i7> <0a334a73-45ef-58ff-7dfd-9df6f4ff290a@arm.com> <20201106105514.bhtdklyhn7goml64@vireshk-i7> <7f73bcd6-0f06-4ef0-7f02-0751e6c4d94b@arm.com> <20201109065742.22czfgyjhsjmkytf@vireshk-i7> <2fa8a5c0-f66d-34bc-7f1c-8462e7532e0a@arm.com> <20201117101128.6uapqg56arwqmm5p@vireshk-i7> From: Nicola Mazzucato Message-ID: <0858962e-3a30-d177-594b-bb8e3149dd8d@arm.com> Date: Tue, 17 Nov 2020 10:47:16 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: <20201117101128.6uapqg56arwqmm5p@vireshk-i7> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Viresh, On 11/17/20 10:11 AM, Viresh Kumar wrote: > On 16-11-20, 11:33, Lukasz Luba wrote: >> On 11/9/20 6:57 AM, Viresh Kumar wrote: >>> On 06-11-20, 11:14, Lukasz Luba wrote: >>>> I also had similar doubts, because if we make frequency requests >>>> independently for each CPU, why not having N cooling devs, which >>>> will set independently QoS max freq for them... >>>> >>>> What convinced me: >>>> EAS and FIE would know the 'real' frequency of the cluster, IPA >>>> can use it also and have only one cooling device per cluster. >>>> >>>> We would like to keep this old style 'one cooling device per cpuset'. >>>> I don't have strong opinion and if it would appear that there are >>>> some errors in freq estimation for cluster, then maybe it does make >>>> more sense to have cdev per CPU... >>> >>> Let me rephrase my question. What is it that doesn't work _correctly_ >>> with cdev per cpufreq policy in your case? What doesn't work well if >>> the thermal stuff keeps looking at only the related_cpus thing and not >>> the cpu-perf-dependencies thing? >>> >> >> We don't have a platform which would be this per-cpu freq request, yet. >> Thus it's hard to answer your question. The EAS would work in 'old >> style' - cluster mode. I don't know how IPA would work on such HW >> and SW configuration. To figure this out I need a real platform. > > Hmm, so who are going to be the users of this new stuff (dependent > CPUs) ? In general, any platform that has hardware coordination in place and some components need to use the information. I don't think cpufreq-cooling should be updated, unless there > is a compelling reason to. > > The other one in energy model ? Why does it need this information ? The reasons has probably gone lost in the emails, but in a nutshell EM needs accurate information on performance boundaries to achieve correct task placement. > > Who else ? > Freq-invariance has been mentioned. I suppose the fix will depend on which strategy we prefer to solve this. As a reminder, two solutions: 1) dependent_cpus cpumask in cpufreq and involved entities pick this info or 2) dependent_cpus cpumask in driver but some entities' interfaces may need to change Hope it helps, Nicola