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_1 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 E1295C352A4 for ; Mon, 10 Feb 2020 12:09:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C0DB520838 for ; Mon, 10 Feb 2020 12:09:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727974AbgBJMJI (ORCPT ); Mon, 10 Feb 2020 07:09:08 -0500 Received: from foss.arm.com ([217.140.110.172]:59386 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727570AbgBJMHY (ORCPT ); Mon, 10 Feb 2020 07:07:24 -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 DD9A81FB; Mon, 10 Feb 2020 04:07:23 -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 C0B883F6CF; Mon, 10 Feb 2020 04:07:20 -0800 (PST) Subject: Re: [Patch v9 0/8] Introduce Thermal Pressure To: Thara Gopinath , mingo@redhat.com, peterz@infradead.org, 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 Cc: 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> From: Dietmar Eggemann Message-ID: <95164e1d-12e4-b155-f0d6-f869ee982aae@arm.com> Date: Mon, 10 Feb 2020 13:07:19 +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: <1580250967-4386-1-git-send-email-thara.gopinath@linaro.org> 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 28/01/2020 23:35, Thara Gopinath wrote: > Thermal governors can respond to an overheat event of a cpu by > capping the cpu's maximum possible frequency. This in turn > means that the maximum available compute capacity of the > cpu is restricted. But today in the kernel, task scheduler is > not notified of capping of maximum frequency of a cpu. > In other words, scheduler is unaware of maximum capacity > restrictions placed on a cpu due to thermal activity. > This patch series attempts to address this issue. > The benefits identified are better task placement among available > cpus in event of overheating which in turn leads to better > performance numbers. > > The reduction in the maximum possible capacity of a cpu due to a > thermal event can be considered as thermal pressure. Instantaneous > thermal pressure is hard to record and can sometime be erroneous > as there can be mismatch between the actual capping of capacity > and scheduler recording it. Thus solution is to have a weighted > average per cpu value for thermal pressure over time. > The weight reflects the amount of time the cpu has spent at a > capped maximum frequency. Since thermal pressure is recorded as > an average, it must be decayed periodically. Exisiting algorithm > in the kernel scheduler pelt framework is re-used to calculate > the weighted average. This patch series also defines a sysctl > inerface to allow for a configurable decay period. > > Regarding testing, basic build, boot and sanity testing have been > performed on db845c platform with debian file system. > Further, dhrystone and hackbench tests have been > run with the thermal pressure algorithm. During testing, due to > constraints of step wise governor in dealing with big little systems, > trip point 0 temperature was made assymetric between cpus in little > cluster and big cluster; the idea being that > big core will heat up and cpu cooling device will throttle the > frequency of the big cores faster, there by limiting the maximum available > capacity and the scheduler will spread out tasks to little cores as well. > > Test Results > > Hackbench: 1 group , 30000 loops, 10 runs > Result SD > (Secs) (% of mean) > No Thermal Pressure 14.03 2.69% > Thermal Pressure PELT Algo. Decay : 32 ms 13.29 0.56% > Thermal Pressure PELT Algo. Decay : 64 ms 12.57 1.56% > Thermal Pressure PELT Algo. Decay : 128 ms 12.71 1.04% > Thermal Pressure PELT Algo. Decay : 256 ms 12.29 1.42% > Thermal Pressure PELT Algo. Decay : 512 ms 12.42 1.15% > > Dhrystone Run Time : 20 threads, 3000 MLOOPS > Result SD > (Secs) (% of mean) > No Thermal Pressure 9.452 4.49% > Thermal Pressure PELT Algo. Decay : 32 ms 8.793 5.30% > Thermal Pressure PELT Algo. Decay : 64 ms 8.981 5.29% > Thermal Pressure PELT Algo. Decay : 128 ms 8.647 6.62% > Thermal Pressure PELT Algo. Decay : 256 ms 8.774 6.45% > Thermal Pressure PELT Algo. Decay : 512 ms 8.603 5.41% What do we do on systems on which one Frequency domain spawns all the CPUs (e.g. Hikey620)? perf stat --null --repeat 10 -- perf bench sched messaging -g 10 -l 1000 # Running 'sched/messaging' benchmark: # 20 sender and receiver processes per group # 10 groups == 400 processes run Total time: 4.697 [sec] # Running 'sched/messaging' benchmark: [ 8082.882751] hisi_thermal f7030700.tsensor: sensor <2> THERMAL ALARM: 66385 > 65000 # 20 sender and receiver processes per group # 10 groups == 400 processes run Total time: 4.910 [sec] # Running 'sched/messaging' benchmark: [ 8091.070386] CPU3 cpus=0-7 th_pressure=205 [ 8091.178390] CPU3 cpus=0-7 th_pressure=0 [ 8091.286389] CPU3 cpus=0-7 th_pressure=205 [ 8091.398397] CPU3 cpus=0-7 th_pressure=0