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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_2 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 6CD7AC10F14 for ; Fri, 4 Oct 2019 03:31:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4E56221848 for ; Fri, 4 Oct 2019 03:31:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387493AbfJDDbd (ORCPT ); Thu, 3 Oct 2019 23:31:33 -0400 Received: from mga09.intel.com ([134.134.136.24]:27494 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387463AbfJDDbd (ORCPT ); Thu, 3 Oct 2019 23:31:33 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by orsmga102.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 03 Oct 2019 20:31:32 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.67,254,1566889200"; d="scan'208";a="204174052" Received: from spandruv-mobl3.jf.intel.com ([10.255.229.152]) by orsmga002.jf.intel.com with ESMTP; 03 Oct 2019 20:31:31 -0700 Message-ID: <5d6d601d2647644238fc51621407061e1c29320d.camel@linux.intel.com> Subject: Re: [PATCH v2 2/2] cpufreq: intel_pstate: Conditional frequency invariant accounting From: Srinivas Pandruvada To: "Rafael J. Wysocki" , Giovanni Gherdovich Cc: Thomas Gleixner , Ingo Molnar , Peter Zijlstra , Borislav Petkov , Len Brown , x86@kernel.org, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, Mel Gorman , Matt Fleming , Viresh Kumar , Juri Lelli , Paul Turner , Vincent Guittot , Quentin Perret , Dietmar Eggemann , Doug Smythies Date: Thu, 03 Oct 2019 20:31:30 -0700 In-Reply-To: <13106850.QMtCbivBLn@kreacher> References: <20191002122926.385-1-ggherdovich@suse.cz> <20191002122926.385-3-ggherdovich@suse.cz> <13106850.QMtCbivBLn@kreacher> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.28.5 (3.28.5-3.fc28) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. > > So is the real concern that intel_pstate in the "active" mode reads > the MPERF > and APERF MSRs by itself and that kind of duplicates what the scale > invariance > code does and is redundant etc? It is redundant in non-HWP mode. In HWP and performance (active mode) we don't use atleast at this time. Thanks Srinivas