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=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 73B53C4360C for ; Fri, 4 Oct 2019 08:30:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7D4A8222BE for ; Fri, 4 Oct 2019 08:30:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1570177804; bh=oUkAiv52stmme9du1zU9yiV89FwHarOwljeSWvMYvMQ=; h=References:In-Reply-To:From:Date:Subject:To:Cc:List-ID:From; b=qXL75Ia1eeUo8+EQDxUYzeoGu2CmG5gN2oyGvpXnNM82k/e7qWNecrYoYCKm3kU25 JIymZ/SZs+J2xRDPhODEhlTYeUfHgDDq1EXSNHcAlp8kzjsGEJT9/NA2OUGx/EzUhK hcjVTq9HfAFc3/OpXFQFCHPuSGoGISrhEZPnEeCk= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730394AbfJDIaE (ORCPT ); Fri, 4 Oct 2019 04:30:04 -0400 Received: from mail-oi1-f193.google.com ([209.85.167.193]:43916 "EHLO mail-oi1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725730AbfJDIaD (ORCPT ); Fri, 4 Oct 2019 04:30:03 -0400 Received: by mail-oi1-f193.google.com with SMTP id t84so5044031oih.10; Fri, 04 Oct 2019 01:30:02 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=k0lh1A+ZoVRyrerJZUky2BuZ3TgVLKznaFWvWQ8x4rk=; b=Tk3Kdt4R2c6rCQzLA5fnTvOFa0w8M2GaSWxgk4NikNuQomCdI1Qz0FtBIkHBfGtZ14 3m4CvFGC0HEVQdazaVcyRGoCMQ7RcBhRcVfBNOcgpCBWP3vKAGHdnNYR/MamZQtzMZOH DDcZgKEdiM/WN6jbH1Y7a70FJhxHV1QB2aoaFtAmYHC+Nh1AsOwzg/H1rUl5diAITuzv cuVWlb4aU5tMVU1hQhZvbD+FDuHtTzht+gmTjIrF53rYy1awH1Pg+7RY9WgrqbY8SK/T szXCnQbeYdVhIYn8J2hrFpbhJXFUFGH3k6DPRGboeWDRan0oINCIozLGokuqB9qiono7 qnQQ== X-Gm-Message-State: APjAAAW+KT1Csd3xwY9GpNTxufvcsDuDy3OxAvFT4pdS+Bu0IqFA9yvL vXWr+8pqwDm7ts3HR2S9Zxa6Tj0RaKjyPhL+DmM= X-Google-Smtp-Source: APXvYqyuckAxWhmAzq3x/bMhAToNURXcUGJImkqB+8HiT3GnE1LomAaWEgdqTF4QOFmtv2kSMA2wQPPJrAdm0mvj95w= X-Received: by 2002:aca:4890:: with SMTP id v138mr6300646oia.57.1570177802460; Fri, 04 Oct 2019 01:30:02 -0700 (PDT) MIME-Version: 1.0 References: <20191002122926.385-1-ggherdovich@suse.cz> <20191002122926.385-3-ggherdovich@suse.cz> <13106850.QMtCbivBLn@kreacher> <5d6d601d2647644238fc51621407061e1c29320d.camel@linux.intel.com> <1570177786.30086.1.camel@suse.cz> In-Reply-To: <1570177786.30086.1.camel@suse.cz> From: "Rafael J. Wysocki" Date: Fri, 4 Oct 2019 10:29:51 +0200 Message-ID: Subject: Re: [PATCH v2 2/2] cpufreq: intel_pstate: Conditional frequency invariant accounting To: Giovanni Gherdovich Cc: Srinivas Pandruvada , "Rafael J. Wysocki" , Thomas Gleixner , Ingo Molnar , Peter Zijlstra , Borislav Petkov , Len Brown , "the arch/x86 maintainers" , Linux PM , Linux Kernel Mailing List , Mel Gorman , Matt Fleming , Viresh Kumar , Juri Lelli , Paul Turner , Vincent Guittot , Quentin Perret , Dietmar Eggemann , Doug Smythies Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 4, 2019 at 10:24 AM Giovanni Gherdovich wrote: > > On Thu, 2019-10-03 at 20:31 -0700, Srinivas Pandruvada wrote: > > On Thu, 2019-10-03 at 20:05 +0200, Rafael J. Wysocki wrote: > > > On Wednesday, October 2, 2019 2:29:26 PM CEST Giovanni Gherdovich > > > wrote: > > > > From: Srinivas Pandruvada > > > > > > > > intel_pstate has two operating modes: active and passive. In "active" > > > > mode, the in-built scaling governor is used and in "passive" mode, the > > > > driver can be used with any governor like "schedutil". In "active" mode > > > > the utilization values from schedutil is not used and there is a > > > > requirement from high performance computing use cases, not to readas > > > > well any APERF/MPERF MSRs. > > > > > > Well, this isn't quite convincing. > > > > > > In particular, I don't see why the "don't read APERF/MPERF MSRs" argument > > > applies *only* to intel_pstate in the "active" mode. What about > > > intel_pstate in the "passive" mode combined with the "performance" > > > governor? Or any other governor different from "schedutil" for that > > > matter? > > > > > > And what about acpi_cpufreq combined with any governor different from > > > "schedutil"? > > > > > > Scale invariance is not really needed in all of those cases right now > > > AFAICS, or is it? > > > > Correct. This is just part of the patch to disable in active mode > > (particularly in HWP and performance mode). > > > > But this patch is 2 years old. The folks who wanted this, disable > > intel-pstate and use userspace governor with acpi-cpufreq. So may be > > better to address those cases too. > > I disagree with "scale invariance is needed only by the schedutil governor"; > the two other users are the CPU's estimated utilization in the wakeup path, > via cpu_util_without(), as well as the load-balance path, via cpu_util() which > is used by update_sg_lb_stats(). OK, so there are reasons to run the scale invariance code which are not related to the cpufreq governor in use. I wonder then why those reasons are not relevant for intel_pstate in the "active" mode. > Also remember that scale invariance is applied to both PELT signals util_avg > and load_avg; schedutil uses the former but not the latter. > > I understand Srinivas patch to disable MSR accesses during the tick as a > band-aid solution to address a specific use case he cares about, but I don't > think that extending this approach to any non-schedutil governor is a good > idea -- you'd be killing load balancing in the process. But that is also the case for intel_pstate in the "active" mode, isn't it?