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=-8.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 4CA9EC433E2 for ; Wed, 2 Sep 2020 13:49:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2936820767 for ; Wed, 2 Sep 2020 13:49:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726858AbgIBNtx (ORCPT ); Wed, 2 Sep 2020 09:49:53 -0400 Received: from foss.arm.com ([217.140.110.172]:38380 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727852AbgIBNtx (ORCPT ); Wed, 2 Sep 2020 09:49:53 -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 888AED6E; Wed, 2 Sep 2020 06:24:32 -0700 (PDT) Received: from bogus (unknown [10.57.4.218]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 1F2923F885; Wed, 2 Sep 2020 06:24:31 -0700 (PDT) Date: Wed, 2 Sep 2020 14:24:28 +0100 From: Sudeep Holla To: Ionela Voinescu Cc: rjw@rjwysocki.net, viresh.kumar@linaro.org, dietmar.eggemann@arm.com, catalin.marinas@arm.com, will@kernel.org, valentin.schneider@arm.com, linux-pm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v5 5/5] arch_topology, arm, arm64: define arch_scale_freq_invariant() Message-ID: <20200902132428.GD25462@bogus> References: <20200901205549.30096-1-ionela.voinescu@arm.com> <20200901205549.30096-6-ionela.voinescu@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200901205549.30096-6-ionela.voinescu@arm.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org On Tue, Sep 01, 2020 at 09:55:49PM +0100, Ionela Voinescu wrote: > From: Valentin Schneider > > arch_scale_freq_invariant() is used by schedutil to determine whether > the scheduler's load-tracking signals are frequency invariant. Its > definition is overridable, though by default it is hardcoded to 'true' > if arch_scale_freq_capacity() is defined ('false' otherwise). > > This behaviour is not overridden on arm, arm64 and other users of the > generic arch topology driver, which is somewhat precarious: > arch_scale_freq_capacity() will always be defined, yet not all cpufreq > drivers are guaranteed to drive the frequency invariance scale factor > setting. In other words, the load-tracking signals may very well *not* > be frequency invariant. > > Now that cpufreq can be queried on whether the current driver is driving > the Frequency Invariance (FI) scale setting, the current situation can > be improved. This combines the query of whether cpufreq supports the > setting of the frequency scale factor, with whether all online CPUs are > counter-based FI enabled. > > While cpufreq FI enablement applies at system level, for all CPUs, > counter-based FI support could also be used for only a subset of CPUs to > set the invariance scale factor. Therefore, if cpufreq-based FI support > is present, we consider the system to be invariant. If missing, we > require all online CPUs to be counter-based FI enabled in order for the > full system to be considered invariant. > > If the system ends up not being invariant, a new condition is needed in > the counter initialization code that disables all scale factor setting > based on counters. > > Precedence of counters over cpufreq use is not important here. The > invariant status is only given to the system if all CPUs have at least > one method of setting the frequency scale factor. > > Signed-off-by: Valentin Schneider > Signed-off-by: Ionela Voinescu > Acked-by: Catalin Marinas > Acked-by: Viresh Kumar > Cc: Catalin Marinas > Cc: Will Deacon > Cc: Sudeep Holla Reviewed-by: Sudeep Holla -- Regards, Sudeep