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=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 00B63C433DF for ; Sat, 20 Jun 2020 22:28:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D986E246E8 for ; Sat, 20 Jun 2020 22:28:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728357AbgFTW22 (ORCPT ); Sat, 20 Jun 2020 18:28:28 -0400 Received: from foss.arm.com ([217.140.110.172]:51632 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727930AbgFTW22 (ORCPT ); Sat, 20 Jun 2020 18:28:28 -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 608BCD6E; Sat, 20 Jun 2020 15:28:27 -0700 (PDT) Received: from e113632-lin (e113632-lin.cambridge.arm.com [10.1.194.46]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 7C1623F73C; Sat, 20 Jun 2020 15:28:25 -0700 (PDT) References: <20200614010755.9129-1-valentin.schneider@arm.com> <20200614010755.9129-2-valentin.schneider@arm.com> <20200620174912.GA18358@arm.com> User-agent: mu4e 0.9.17; emacs 26.3 From: Valentin Schneider To: Ionela Voinescu Cc: Vincent Guittot , Juri Lelli , "open list\:THERMAL" , Peter Zijlstra , Viresh Kumar , Amit Daniel Kachhap , Daniel Lezcano , Russell King , Thara Gopinath , linux-kernel , Sudeep Holla , Dietmar Eggemann , Ingo Molnar , LAK Subject: Re: [PATCH 1/3] thermal/cpu-cooling, sched/core: Cleanup thermal pressure definition In-reply-to: <20200620174912.GA18358@arm.com> Date: Sat, 20 Jun 2020 23:28:19 +0100 Message-ID: MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 20/06/20 18:49, Ionela Voinescu wrote: > Hi Vincent, > > On Thursday 18 Jun 2020 at 17:03:24 (+0200), Vincent Guittot wrote: >> On Sun, 14 Jun 2020 at 03:10, Valentin Schneider >> wrote: > [..] >> > diff --git a/drivers/thermal/cpufreq_cooling.c b/drivers/thermal/cpufreq_cooling.c >> > index e297e135c031..a1efd379b683 100644 >> > --- a/drivers/thermal/cpufreq_cooling.c >> > +++ b/drivers/thermal/cpufreq_cooling.c >> > @@ -417,6 +417,11 @@ static int cpufreq_get_cur_state(struct thermal_cooling_device *cdev, >> > return 0; >> > } >> > >> > +__weak void >> > +arch_set_thermal_pressure(const struct cpumask *cpus, unsigned long th_pressure) >> > +{ >> > +} >> >> Having this weak function declared in cpufreq_cooling is weird. This >> means that we will have to do so for each one that wants to use it. >> >> Can't you declare an empty function in a common header file ? > > Do we expect anyone other than cpufreq_cooling to call > arch_set_thermal_pressure()? > > I'm not against any of the options, either having it here as a week > default definition (same as done for arch_set_freq_scale() in cpufreq.c) > or in a common header (as done for arch_scale_freq_capacity() in sched.h). > Same thoughts here; I was going for the arch_set_freq_scale() way. > But for me, Valentin's implementation seems more natural as setters are > usually only called from within the framework that does the control > (throttling for thermal or frequency setting for cpufreq) and we > probably want to think twice if we want to call them from other places. > Well TBH I was tempted to go the other way and keep the definition in core.c, given a simple per-cpu value is fairly generic. More precisely, it seems somewhat awkward that architectures have to redefine those interfaces when, given what cpufreq_cooling is doing, they'll have to go for per-cpu storage in some way or another. I ultimately decided against it, seeing as it isn't too difficult to come up with other drivers of thermal pressure. There was that TDP-bound thing [1], where IIUC you could end up with throttling not because of thermal but because of power constraints. And then there's always FW that can cap stuff as a last resort, and some architectures will want to inform the scheduler of that when/if they'll be able to query FW for that. [1]: 20200428032258.2518-1-currojerez@riseup.net > Thanks, > Ionela.