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=-5.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 CCA72C2D0B1 for ; Tue, 4 Feb 2020 08:39:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9D6A12051A for ; Tue, 4 Feb 2020 08:39:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726362AbgBDIjY (ORCPT ); Tue, 4 Feb 2020 03:39:24 -0500 Received: from foss.arm.com ([217.140.110.172]:34400 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725834AbgBDIjY (ORCPT ); Tue, 4 Feb 2020 03:39:24 -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 8084130E; Tue, 4 Feb 2020 00:39:23 -0800 (PST) Received: from [192.168.0.7] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 743BE3F6CF; Tue, 4 Feb 2020 00:39:20 -0800 (PST) Subject: Re: [Patch v9 7/8] sched/fair: Enable tuning of decay period To: Peter Zijlstra , Thara Gopinath Cc: Randy Dunlap , mingo@redhat.com, ionela.voinescu@arm.com, vincent.guittot@linaro.org, rui.zhang@intel.com, qperret@google.com, daniel.lezcano@linaro.org, viresh.kumar@linaro.org, rostedt@goodmis.org, will@kernel.org, catalin.marinas@arm.com, sudeep.holla@arm.com, juri.lelli@redhat.com, corbet@lwn.net, linux-kernel@vger.kernel.org, amit.kachhap@gmail.com, javi.merino@kernel.org, amit.kucheria@verdurent.com References: <1580250967-4386-1-git-send-email-thara.gopinath@linaro.org> <1580250967-4386-8-git-send-email-thara.gopinath@linaro.org> <4eb10687-1a62-cee3-7285-3f50cc023071@infradead.org> <5E380D1D.7020500@linaro.org> <20200203155549.GL14914@hirez.programming.kicks-ass.net> From: Dietmar Eggemann Message-ID: Date: Tue, 4 Feb 2020 09:39:12 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <20200203155549.GL14914@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/02/2020 16:55, Peter Zijlstra wrote: > On Mon, Feb 03, 2020 at 07:07:57AM -0500, Thara Gopinath wrote: >> On 01/28/2020 06:56 PM, Randy Dunlap wrote: >>> Hi, >>> >>> On 1/28/20 2:36 PM, Thara Gopinath wrote: >>>> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt >>>> index e35b28e..be4147b 100644 >>>> --- a/Documentation/admin-guide/kernel-parameters.txt >>>> +++ b/Documentation/admin-guide/kernel-parameters.txt >>>> @@ -4376,6 +4376,11 @@ >>>> incurs a small amount of overhead in the scheduler >>>> but is useful for debugging and performance tuning. >>>> >>>> + sched_thermal_decay_shift= >>>> + [KNL, SMP] Set decay shift for thermal pressure signal. >>>> + Format: integer between 0 and 10 >>>> + Default is 0. >>>> + >>> >>> That tells an admin [or any reader] almost nothing about this kernel parameter >>> or what it does. And nothing about what unit the value is in. >>> Does the value 0 disable this feature? >> >> Thanks for the review. 0 does not disable "thermal pressure" feature. 0 >> means the default decay period for averaging PELT signals (which is >> usually 32 but configurable) will also be applied for thermal pressure >> signal. A shift will shift the default decay period. >> >> You are right. It needs more explanation here. I will fix it and send v10. > > Or just send an update for this patch? I'm thinking most of this is > looking good. I do agree. IMHO, there are just two little things outstanding: (1) arch_scale_thermal_pressure() instead of arch_cpu_thermal_pressure() in v8 4/7 (2) guarding of thermal pressure code in Arm's arch_topology driver w/ CONFIG_HAVE_SCHED_THERMAL_PRESSURE plus disabling it by default for Arm64.