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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 CC661C33CB7 for ; Fri, 31 Jan 2020 17:31:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A2A8520663 for ; Fri, 31 Jan 2020 17:31:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726969AbgAaRbB (ORCPT ); Fri, 31 Jan 2020 12:31:01 -0500 Received: from foss.arm.com ([217.140.110.172]:37754 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726139AbgAaRbB (ORCPT ); Fri, 31 Jan 2020 12:31:01 -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 003FCFEC; Fri, 31 Jan 2020 09:31:01 -0800 (PST) Received: from [10.37.12.54] (unknown [10.37.12.54]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 0E9723F68E; Fri, 31 Jan 2020 09:30:49 -0800 (PST) Subject: Re: [PATCH 3/3] ARM: exynos_defconfig: Enable Energy Model framework To: Krzysztof Kozlowski Cc: kgene@kernel.org, linux-arm-kernel@lists.infradead.org, "linux-samsung-soc@vger.kernel.org" , "linux-kernel@vger.kernel.org" , devicetree@vger.kernel.org, linux-pm@vger.kernel.org, myungjoo.ham@samsung.com, kyungmin.park@samsung.com, Chanwoo Choi , robh+dt@kernel.org, mark.rutland@arm.com, =?UTF-8?Q?Bart=c5=82omiej_=c5=bbo=c5=82nierkiewicz?= , dietmar.eggemann@arm.com References: <20200127215453.15144-1-lukasz.luba@arm.com> <20200127215453.15144-4-lukasz.luba@arm.com> From: Lukasz Luba Message-ID: Date: Fri, 31 Jan 2020 17:30:46 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed 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 Hi Krzysztof, On 1/31/20 1:16 PM, Krzysztof Kozlowski wrote: > On Mon, 27 Jan 2020 at 22:55, wrote: >> >> From: Lukasz Luba >> >> Enable the Energy Model (EM) brings possibility to use Energy Aware >> Scheduler (EAS). This compiles the EM but does not enable to run EAS in >> default. The EAS only works with SchedUtil - a CPUFreq governor which >> handles direct requests from the scheduler for the frequency change. Thus, >> to make EAS working in default, the SchedUtil governor should be >> configured as default CPUFreq governor. > > Full stop. That's enough of needed explanation of schedutil. OK > >> Although, the EAS might be enabled >> in runtime, when the EM is present for CPUs, the SchedUtil is compiled and >> then set as CPUFreq governor, i.e.: >> >> echo schedutil > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor >> echo schedutil > /sys/devices/system/cpu/cpu4/cpufreq/scaling_governor >> >> To check if EAS is ready to work, the read output from the command below >> should show '1': >> cat /proc/sys/kernel/sched_energy_aware >> >> To disable EAS in runtime simply 'echo 0' to the file above. > > Not related to this commit. If you were implemeting here > schedutil/EAS, then it makes sense to post all this. However what's > the point to describe it in every defconfig change? I will drop it. > >> Some test results, which stress the scheduler on Odroid-XU3: >> hackbench -l 500 -s 4096 >> With mainline code and with this patch set. > > Skip the last sentence - duplicated information. OK > >> >> The tests have been made with and without CONFIG_PROVE_LOCKING (PL) >> (which is set to =y in default exynos_defconfig) >> >> | this patch set | mainline > > The commit will be applied on its own branch so the meaning of "this > patch set" will be lost. Maybe just "before/after"? OK > >> |-----------------------------------------------|--------------- >> | performance | SchedUtil | SchedUtil | performance >> | governor | governor | governor | governor >> | | w/o EAS | w/ EAS | >> ----------------|---------------|---------------|---------------|--------------- >> hackbench w/ PL | 12.7s | 11.7s | 12.0s | 13.0s - 12.2s >> hackbench w/o PL| 9.2s | 8.1s | 8.2s | 9.2s - 8.4s > > Why does the performance different before and after this patch? Probably due to better locality and cache utilization. I can see that there is ~700k context switches vs ~450k and ~160k migrations vs ~50k. If you need to communicate two threads in different clusters, it will go through CCI. > > Mention - lower better (?). Space between number and unit... or better > mention [s] in column title. OK > > And last but not least: > Why this patch is separate from 1/3? I don't get the need of splitting them. As mentioned in response to patch 1/3. The fist patch would create MC domain, something different than Energy Model or EAS. The decisions in the scheduler would be different. I can merge 1/3 and 3/3 if you like, though. Regards, Lukasz > > Best regards, > Krzysztof >