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=-4.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,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 CE674C433EB for ; Tue, 28 Jul 2020 15:41:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B070620786 for ; Tue, 28 Jul 2020 15:41:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730821AbgG1Plq (ORCPT ); Tue, 28 Jul 2020 11:41:46 -0400 Received: from cloudserver094114.home.pl ([79.96.170.134]:59548 "EHLO cloudserver094114.home.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731019AbgG1Plp (ORCPT ); Tue, 28 Jul 2020 11:41:45 -0400 Received: from 89-64-88-69.dynamic.chello.pl (89.64.88.69) (HELO kreacher.localnet) by serwer1319399.home.pl (79.96.170.134) with SMTP (IdeaSmtpServer 0.83.415) id a18b10c115136856; Tue, 28 Jul 2020 17:41:43 +0200 From: "Rafael J. Wysocki" To: Francisco Jerez Cc: "Rafael J. Wysocki" , Linux PM , Linux Documentation , LKML , Peter Zijlstra , Srinivas Pandruvada , Giovanni Gherdovich , Doug Smythies Subject: Re: [PATCH] cpufreq: intel_pstate: Implement passive mode with HWP enabled Date: Tue, 28 Jul 2020 17:41:42 +0200 Message-ID: <1884886.tmXHBG24oC@kreacher> In-Reply-To: <87mu3thiz5.fsf@riseup.net> References: <3955470.QvD6XneCf3@kreacher> <87mu3thiz5.fsf@riseup.net> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Tuesday, July 21, 2020 1:20:14 AM CEST Francisco Jerez wrote: > [cut] > > If there is a bug, then what exactly is it, from the users' perspective? > > > > It can be reproduced easily as follows: > > | echo 1 > /sys/devices/system/cpu/intel_pstate/hwp_dynamic_boost > | for p in /sys/devices/system/cpu/cpufreq/policy*/energy_performance_preference; do echo performance > $p; done > > Let's make sure that the EPP updates landed on the turbostat output: > > |[..] > | Core CPU Avg_MHz Busy% Bzy_MHz HWP_REQ > | - - 1 0.05 2396 0x0000000000000000 > | 0 0 1 0.05 2153 0x0000000000002704 > | 0 4 1 0.04 2062 0x0000000000002704 > | 1 1 1 0.02 2938 0x0000000000002704 > | 1 5 2 0.09 2609 0x0000000000002704 > | 2 2 1 0.04 1857 0x0000000000002704 > | 2 6 1 0.05 2561 0x0000000000002704 > | 3 3 0 0.01 1883 0x0000000000002704 > | 3 7 2 0.07 2703 0x0000000000002704 > |[..] > > Now let's do some non-trivial IO activity in order to trigger HWP > dynamic boost, and watch while random CPUs start losing their EPP > setting requested via sysfs: > > |[..] > | Core CPU Avg_MHz Busy% Bzy_MHz HWP_REQ > | - - 16 0.81 2023 0x0000000000000000 > | 0 0 7 0.66 1069 0x0000000080002704 > ^^ > | 0 4 24 2.19 1116 0x0000000080002704 > ^^ > | 1 1 18 0.68 2618 0x0000000000002704 > | 1 5 1 0.03 2005 0x0000000000002704 > | 2 2 2 0.07 2512 0x0000000000002704 > | 2 6 33 1.35 2402 0x0000000000002704 > | 3 3 1 0.04 2470 0x0000000000002704 > | 3 7 45 1.42 3185 0x0000000080002704 > ^^ Actually, that's because intel_pstate_hwp_boost_up() and intel_pstate_hwp_boost_down() use the hwp_req_cached value for updating the HWP Request MSR and that is only written to by intel_pstate_hwp_set() which is only invoked on policy changes, so the MSR writes from intel_pstate_set_energy_pref_index() basically get discarded. So this is a matter of synchronizing intel_pstate_set_policy() with intel_pstate_set_energy_pref_index() and they both acquire intel_pstate_limits_lock already, so this shouldn't be too difficult to fix. Let me cut a patch for that.