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=-15.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_2 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 D9C4CC433E9 for ; Fri, 5 Feb 2021 07:08:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9BB1C64FB9 for ; Fri, 5 Feb 2021 07:08:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231144AbhBEHIe (ORCPT ); Fri, 5 Feb 2021 02:08:34 -0500 Received: from mx2.suse.de ([195.135.220.15]:41556 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230516AbhBEHIU (ORCPT ); Fri, 5 Feb 2021 02:08:20 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 2D16EACBA; Fri, 5 Feb 2021 07:07:38 +0000 (UTC) Message-ID: <1612508857.19825.7.camel@suse.cz> Subject: Re: [PATCH v1 2/2] cpufreq: ACPI: Update arch scale-invariance max perf ratio if CPPC is not there From: Giovanni Gherdovich To: "Rafael J. Wysocki" , Linux PM Cc: LKML , Linux ACPI , Peter Zijlstra , Srinivas Pandruvada , Viresh Kumar , Mel Gorman , Michael Larabel , Juri Lelli , Vincent Guittot Date: Fri, 05 Feb 2021 08:07:37 +0100 In-Reply-To: <9510730.kuOQ4KzHjt@kreacher> References: <13690581.X0sz4iL7V8@kreacher> <9510730.kuOQ4KzHjt@kreacher> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.26.6 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2021-02-04 at 18:34 +0100, Rafael J. Wysocki wrote: > From: Rafael J. Wysocki > > If the maximum performance level taken for computing the > arch_max_freq_ratio value used in the x86 scale-invariance code is > higher than the one corresponding to the cpuinfo.max_freq value > coming from the acpi_cpufreq driver, the scale-invariant utilization > falls below 100% even if the CPU runs at cpuinfo.max_freq or slightly > faster, which causes the schedutil governor to select a frequency > below cpuinfo.max_freq. That frequency corresponds to a frequency > table entry below the maximum performance level necessary to get to > the "boost" range of CPU frequencies which prevents "boost" > frequencies from being used in some workloads. > > While this issue is related to scale-invariance, it may be amplified > by commit db865272d9c4 ("cpufreq: Avoid configuring old governors as > default with intel_pstate") from the 5.10 development cycle which > made it extremely easy to default to schedutil even if the preferred > driver is acpi_cpufreq as long as intel_pstate is built too, because > the mere presence of the latter effectively removes the ondemand > governor from the defaults. Distro kernels are likely to include > both intel_pstate and acpi_cpufreq on x86, so their users who cannot > use intel_pstate or choose to use acpi_cpufreq may easily be > affectecd by this issue. > > If CPPC is available, it can be used to address this issue by > extending the frequency tables created by acpi_cpufreq to cover the > entire available frequency range (including "boost" frequencies) for > each CPU, but if CPPC is not there, acpi_cpufreq has no idea what > the maximum "boost" frequency is and the frequency tables created by > it cannot be extended in a meaningful way, so in that case make it > ask the arch scale-invariance code to to use the "nominal" performance > level for CPU utilization scaling in order to avoid the issue at hand. > > Fixes: db865272d9c4 ("cpufreq: Avoid configuring old governors as default with intel_pstate") > Signed-off-by: Rafael J. Wysocki > --- > arch/x86/kernel/smpboot.c | 1 + > drivers/cpufreq/acpi-cpufreq.c | 8 ++++++++ > 2 files changed, 9 insertions(+) > > Index: linux-pm/drivers/cpufreq/acpi-cpufreq.c > =================================================================== > --- linux-pm.orig/drivers/cpufreq/acpi-cpufreq.c > +++ linux-pm/drivers/cpufreq/acpi-cpufreq.c > @@ -806,6 +806,14 @@ static int acpi_cpufreq_cpu_init(struct > state_count++; > valid_states++; > data->first_perf_state = valid_states; > + } else { > + /* > + * If the maximum "boost" frequency is unknown, ask the arch > + * scale-invariance code to use the "nominal" performance for > + * CPU utilization scaling so as to prevent the schedutil > + * governor from selecting inadequate CPU frequencies. > + */ > + arch_set_max_freq_ratio(true); > } > > freq_table = kcalloc(state_count, sizeof(*freq_table), GFP_KERNEL); > Index: linux-pm/arch/x86/kernel/smpboot.c > =================================================================== > --- linux-pm.orig/arch/x86/kernel/smpboot.c > +++ linux-pm/arch/x86/kernel/smpboot.c > @@ -1833,6 +1833,7 @@ void arch_set_max_freq_ratio(bool turbo_ > arch_max_freq_ratio = turbo_disabled ? SCHED_CAPACITY_SCALE : > arch_turbo_freq_ratio; > } > +EXPORT_SYMBOL_GPL(arch_set_max_freq_ratio); > > static bool turbo_disabled(void) > { Reviewed-by: Giovanni Gherdovich Thanks, Giovanni