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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8D1EDE7D0A2 for ; Thu, 21 Sep 2023 18:16:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229514AbjIUSQJ (ORCPT ); Thu, 21 Sep 2023 14:16:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41618 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230316AbjIUSPa (ORCPT ); Thu, 21 Sep 2023 14:15:30 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 33AE885D05; Thu, 21 Sep 2023 10:37:47 -0700 (PDT) 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 1AC3114BF; Thu, 21 Sep 2023 02:20:19 -0700 (PDT) Received: from localhost (ionvoi01-desktop.cambridge.arm.com [10.2.78.69]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 8E5C33F59C; Thu, 21 Sep 2023 02:19:41 -0700 (PDT) Date: Thu, 21 Sep 2023 10:19:40 +0100 From: Ionela Voinescu To: Vincent Guittot Cc: linux@armlinux.org.uk, catalin.marinas@arm.com, will@kernel.org, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, sudeep.holla@arm.com, gregkh@linuxfoundation.org, rafael@kernel.org, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, viresh.kumar@linaro.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, linux-pm@vger.kernel.org, conor.dooley@microchip.com, suagrfillet@gmail.com, ajones@ventanamicro.com, lftan@kernel.org Subject: Re: [PATCH 3/4] cpufreq/schedutil: use a fixed reference frequency Message-ID: References: <20230901130312.247719-1-vincent.guittot@linaro.org> <20230901130312.247719-4-vincent.guittot@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230901130312.247719-4-vincent.guittot@linaro.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Friday 01 Sep 2023 at 15:03:11 (+0200), Vincent Guittot wrote: > cpuinfo_max_freq can change at runtime because of boost as example. This > implies that the value could not be the same than the one that has been > used when computing the capacity of a CPU. > > The new arch_scale_freq_ref() returns a fixed and coherent frequency > reference that can be used when computing a frequency based on utilization. > > Use this arch_scale_freq_ref() when available and fallback to > cpuinfo.max_freq otherwise. > > Signed-off-by: Vincent Guittot > --- > kernel/sched/cpufreq_schedutil.c | 29 +++++++++++++++++++++++++++-- > 1 file changed, 27 insertions(+), 2 deletions(-) > > diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c > index 4492608b7d7f..9996ef429e2b 100644 > --- a/kernel/sched/cpufreq_schedutil.c > +++ b/kernel/sched/cpufreq_schedutil.c > @@ -114,6 +114,31 @@ static void sugov_deferred_update(struct sugov_policy *sg_policy) > } > } > > +#ifdef arch_scale_freq_ref > +/** > + * arch_scale_freq_ref_policy - get the reference frequency of a given CPU that > + * has been used to correlate frequency and compute capacity. > + * @cpu: the CPU in question. > + * > + * Return: the reference CPU frequency. > + */ > +static __always_inline > +unsigned long arch_scale_freq_ref_policy(struct cpufreq_policy *policy) This should not be an arch_ function as it's only a wrapper over an arch_ function and not a function that different architectures might implement differently usually in architecture specific code. > +{ > + return arch_scale_freq_ref(policy->cpu); It might make it easier to read if arch_scale_freq_ref() had a default implementation that returned 0. Then this code would simply become: freq = arch_scale_freq_ref(policy->cpu); if (freq) return freq; else if (arch_scale_freq_invariant()) return .. .. This approach is similar to the use of arch_freq_get_on_cpu() in cpufreq.c, and, as there, having a chosen maximum frequency of 0 would not be a valid value. > +} > +#else > +static __always_inline > +unsigned long arch_scale_freq_ref_policy(struct cpufreq_policy *policy) > +{ > + if (arch_scale_freq_invariant()) > + return policy->cpuinfo.max_freq; > + > + > + return policy->cur; > +} > +#endif > + > /** > * get_next_freq - Compute a new frequency for a given cpufreq policy. > * @sg_policy: schedutil policy object to compute the new frequency for. > @@ -139,11 +164,11 @@ static void sugov_deferred_update(struct sugov_policy *sg_policy) > static unsigned int get_next_freq(struct sugov_policy *sg_policy, > unsigned long util, unsigned long max) > { > + unsigned int freq; > struct cpufreq_policy *policy = sg_policy->policy; > - unsigned int freq = arch_scale_freq_invariant() ? > - policy->cpuinfo.max_freq : policy->cur; > > util = map_util_perf(util); > + freq = arch_scale_freq_ref_policy(policy); Given its single use here, it would likely be better to place the code above directly here, rather than create a wrapper over a few lines of code. Hope it helps, Ionela. > freq = map_util_freq(util, freq, max); > > if (freq == sg_policy->cached_raw_freq && !sg_policy->need_freq_update) > -- > 2.34.1 > >