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=-10.4 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 422F7C48BE5 for ; Wed, 16 Jun 2021 17:24:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1A27C613DB for ; Wed, 16 Jun 2021 17:24:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230186AbhFPR0r (ORCPT ); Wed, 16 Jun 2021 13:26:47 -0400 Received: from foss.arm.com ([217.140.110.172]:42728 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229741AbhFPR0r (ORCPT ); Wed, 16 Jun 2021 13:26:47 -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 9AB1E1042; Wed, 16 Jun 2021 10:24:40 -0700 (PDT) Received: from [192.168.178.6] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 868023F70D; Wed, 16 Jun 2021 10:24:37 -0700 (PDT) Subject: Re: [PATCH v4 2/3] sched/fair: Take thermal pressure into account while estimating energy To: Lukasz Luba Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, peterz@infradead.org, rjw@rjwysocki.net, viresh.kumar@linaro.org, vincent.guittot@linaro.org, qperret@google.com, vincent.donnefort@arm.com, Beata.Michalska@arm.com, mingo@redhat.com, juri.lelli@redhat.com, rostedt@goodmis.org, segall@google.com, mgorman@suse.de, bristot@redhat.com, thara.gopinath@linaro.org, amit.kachhap@gmail.com, amitk@kernel.org, rui.zhang@intel.com, daniel.lezcano@linaro.org References: <20210614185815.15136-1-lukasz.luba@arm.com> <20210614191128.22735-1-lukasz.luba@arm.com> <237ef538-c8ca-a103-b2cc-240fc70298fe@arm.com> From: Dietmar Eggemann Message-ID: <9821712d-be27-a2e7-991c-b0010e23fa70@arm.com> Date: Wed, 16 Jun 2021 19:24:36 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org On 15/06/2021 18:09, Lukasz Luba wrote: > > On 6/15/21 4:31 PM, Dietmar Eggemann wrote: >> On 14/06/2021 21:11, Lukasz Luba wrote: [...] >> It's important to highlight that this will only fix this issue between >> schedutil and EAS when it's due to `thermal pressure` (today only via >> CPU cooling). There are other places which could restrict policy->max >> via freq_qos_update_request() and EAS will be unaware of it. > > True, but for this I have some other plans. As long as people are aware of the fact that this was developed to be beneficial for `EAS - IPA` integration, I'm fine with this. [...] >> IMHO, this means that this is catered for the IPA governor then. I'm not >> sure if this would be beneficial when another thermal governor is used? > > Yes, it will be, the cpufreq_set_cur_state() is called by > thermal exported function: > thermal_cdev_update() >   __thermal_cdev_update() >     thermal_cdev_set_cur_state() >       cdev->ops->set_cur_state(cdev, target) > > So it can be called not only by IPA. All governors call it, because > that's the default mechanism. True, but I'm still not convinced that it is useful outside `EAS - IPA`. >> The mechanical side of the code would allow for such benefits, I just >> don't know if their CPU cooling device + thermal zone setups would cater >> for this? > > Yes, it's possible. Even for custom vendor governors (modified clones > of IPA) Let's stick to mainline here ;-) It's complicated enough ... [...] >> Maybe shorter? >> >>          struct cpumask *pd_mask = perf_domain_span(pd); >> -       unsigned long cpu_cap = >> arch_scale_cpu_capacity(cpumask_first(pd_mask)); >> +       int cpu = cpumask_first(pd_mask); >> +       unsigned long cpu_cap = arch_scale_cpu_capacity(cpu); >> +       unsigned long _cpu_cap = cpu_cap - >> arch_scale_thermal_pressure(cpu); >>          unsigned long max_util = 0, sum_util = 0; >> -       unsigned long _cpu_cap = cpu_cap; >> -       int cpu; >> - >> -       _cpu_cap -= arch_scale_thermal_pressure(cpumask_first(pd_mask)); > > Could be, but still, the definitions should be sorted from longest on > top, to shortest at the bottom. I wanted to avoid modifying too many > lines with this simple patch. Only if there are no dependencies, but here we have already `cpu_cap -> pd_mask`. OK, not a big deal. [...] >> There is IPA specific code in cpufreq_set_cur_state() -> >> get_state_freq() which accesses the EM: >> >>      ... >>      return cpufreq_cdev->em->table[idx].frequency; >>      ... >> >> Has it been discussed that the `per-PD max (allowed) CPU capacity` (1) >> could be stored in the EM from there so that code like the EAS wakeup >> code (compute_energy()) could retrieve this information from the EM? > > No, we haven't think about this approach in these patch sets. > The EM structure given to the cpufreq_cooling device and stored in: > cpufreq_cdev->em should not be modified. There are a few places which > receive the EM, but they all should not touch it. For those clients > it's a read-only data structure. > >> And there wouldn't be any need to pass (1) into the EM (like now via >> em_cpu_energy()). >> This would be signalling within the EM compared to external signalling >> via `CPU cooling -> thermal pressure <- EAS wakeup -> EM`. > > I see what you mean, but this might cause some issues in the design > (per-cpu scmi cpu perf control). Let's use this EM pointer gently ;) OK, with the requirement that clients see the EM as ro: Reviewed-by: Dietmar Eggemann