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=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, 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 C5CFEC10DCE for ; Fri, 6 Mar 2020 11:53:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A4A152073B for ; Fri, 6 Mar 2020 11:53:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726300AbgCFLxu (ORCPT ); Fri, 6 Mar 2020 06:53:50 -0500 Received: from foss.arm.com ([217.140.110.172]:60272 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726026AbgCFLxu (ORCPT ); Fri, 6 Mar 2020 06:53:50 -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 4756F31B; Fri, 6 Mar 2020 03:53:49 -0800 (PST) Received: from bogus (e103737-lin.cambridge.arm.com [10.1.197.49]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id EFEAA3F6C4; Fri, 6 Mar 2020 03:53:46 -0800 (PST) Date: Fri, 6 Mar 2020 11:53:41 +0000 From: Sudeep Holla To: Ionela Voinescu Cc: catalin.marinas@arm.com, will@kernel.org, mark.rutland@arm.com, maz@kernel.org, suzuki.poulose@arm.com, lukasz.luba@arm.com, valentin.schneider@arm.com, dietmar.eggemann@arm.com, rjw@rjwysocki.net, pkondeti@codeaurora.org, peterz@infradead.org, mingo@redhat.com, vincent.guittot@linaro.org, viresh.kumar@linaro.org, linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org Subject: Re: [PATCH v6 6/7] arm64: use activity monitors for frequency invariance Message-ID: <20200306115341.GA44221@bogus> References: <20200305090627.31908-1-ionela.voinescu@arm.com> <20200305090627.31908-7-ionela.voinescu@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200305090627.31908-7-ionela.voinescu@arm.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Thu, Mar 05, 2020 at 09:06:26AM +0000, Ionela Voinescu wrote: > The Frequency Invariance Engine (FIE) is providing a frequency > scaling correction factor that helps achieve more accurate > load-tracking. > > So far, for arm and arm64 platforms, this scale factor has been > obtained based on the ratio between the current frequency and the > maximum supported frequency recorded by the cpufreq policy. The > setting of this scale factor is triggered from cpufreq drivers by > calling arch_set_freq_scale. The current frequency used in computation > is the frequency requested by a governor, but it may not be the > frequency that was implemented by the platform. > > This correction factor can also be obtained using a core counter and a > constant counter to get information on the performance (frequency based > only) obtained in a period of time. This will more accurately reflect > the actual current frequency of the CPU, compared with the alternative > implementation that reflects the request of a performance level from > the OS. > > Therefore, implement arch_scale_freq_tick to use activity monitors, if > present, for the computation of the frequency scale factor. > > The use of AMU counters depends on: > - CONFIG_ARM64_AMU_EXTN - depents on the AMU extension being present > - CONFIG_CPU_FREQ - the current frequency obtained using counter > information is divided by the maximum frequency obtained from the > cpufreq policy. > > While it is possible to have a combination of CPUs in the system with > and without support for activity monitors, the use of counters for > frequency invariance is only enabled for a CPU if all related CPUs > (CPUs in the same frequency domain) support and have enabled the core > and constant activity monitor counters. In this way, there is a clear > separation between the policies for which arch_set_freq_scale (cpufreq > based FIE) is used, and the policies for which arch_scale_freq_tick > (counter based FIE) is used to set the frequency scale factor. For > this purpose, a late_initcall_sync is registered to trigger validation > work for policies that will enable or disable the use of AMU counters > for frequency invariance. If CONFIG_CPU_FREQ is not defined, the use > of counters is enabled on all CPUs only if all possible CPUs correctly > support the necessary counters. > > Signed-off-by: Ionela Voinescu > Reviewed-by: Lukasz Luba > Cc: Catalin Marinas > Cc: Will Deacon > Cc: Sudeep Holla > --- > arch/arm64/include/asm/topology.h | 9 ++ > arch/arm64/kernel/cpufeature.c | 4 + > arch/arm64/kernel/topology.c | 180 ++++++++++++++++++++++++++++++ > drivers/base/arch_topology.c | 12 ++ > include/linux/arch_topology.h | 2 + > 5 files changed, 207 insertions(+) > [...] > diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c > index 6119e11a9f95..8d63673c1689 100644 > --- a/drivers/base/arch_topology.c > +++ b/drivers/base/arch_topology.c > @@ -21,6 +21,10 @@ > #include > #include > > +__weak bool arch_freq_counters_available(struct cpumask *cpus) > +{ > + return false; > +} > DEFINE_PER_CPU(unsigned long, freq_scale) = SCHED_CAPACITY_SCALE; > > void arch_set_freq_scale(struct cpumask *cpus, unsigned long cur_freq, > @@ -29,6 +33,14 @@ void arch_set_freq_scale(struct cpumask *cpus, unsigned long cur_freq, > unsigned long scale; > int i; > > + /* > + * If the use of counters for FIE is enabled, just return as we don't > + * want to update the scale factor with information from CPUFREQ. > + * Instead the scale factor will be updated from arch_scale_freq_tick. > + */ > + if (arch_freq_counters_available(cpus)) > + return; > + > scale = (cur_freq << SCHED_CAPACITY_SHIFT) / max_freq; > > for_each_cpu(i, cpus) > diff --git a/include/linux/arch_topology.h b/include/linux/arch_topology.h > index 3015ecbb90b1..1ccdddb541a7 100644 > --- a/include/linux/arch_topology.h > +++ b/include/linux/arch_topology.h > @@ -33,6 +33,8 @@ unsigned long topology_get_freq_scale(int cpu) > return per_cpu(freq_scale, cpu); > } > > +bool arch_freq_counters_available(struct cpumask *cpus); > + > struct cpu_topology { > int thread_id; > int core_id; Sorry for the delay. The arch_topology part looks fine to me. For that part: Acked-by: Sudeep Holla -- Regards, Sudeep