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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 29F7DC07E99 for ; Mon, 5 Jul 2021 08:14:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 06592613B2 for ; Mon, 5 Jul 2021 08:14:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230088AbhGEIQm (ORCPT ); Mon, 5 Jul 2021 04:16:42 -0400 Received: from foss.arm.com ([217.140.110.172]:40288 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230000AbhGEIQk (ORCPT ); Mon, 5 Jul 2021 04:16:40 -0400 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 B0FADD6E; Mon, 5 Jul 2021 01:14:03 -0700 (PDT) Received: from [10.57.13.252] (unknown [10.57.13.252]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 702F53F694; Mon, 5 Jul 2021 01:14:02 -0700 (PDT) Subject: Re: [PATCH AUTOSEL 5.12 62/80] sched/fair: Take thermal pressure into account while estimating energy To: Sasha Levin , stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Peter Zijlstra , Vincent Guittot , Dietmar Eggemann , Greg KH References: <20210704230616.1489200-1-sashal@kernel.org> <20210704230616.1489200-62-sashal@kernel.org> From: Lukasz Luba Message-ID: <54648043-4944-08f9-8ce8-8413d8037450@arm.com> Date: Mon, 5 Jul 2021 09:13:59 +0100 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: <20210704230616.1489200-62-sashal@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Sasha, +CC Greg On 7/5/21 12:05 AM, Sasha Levin wrote: > From: Lukasz Luba > > [ Upstream commit 489f16459e0008c7a5c4c5af34bd80898aa82c2d ] > > Energy Aware Scheduling (EAS) needs to be able to predict the frequency > requests made by the SchedUtil governor to properly estimate energy used > in the future. It has to take into account CPUs utilization and forecast > Performance Domain (PD) frequency. There is a corner case when the max > allowed frequency might be reduced due to thermal. SchedUtil is aware of > that reduced frequency, so it should be taken into account also in EAS > estimations. > > SchedUtil, as a CPUFreq governor, knows the maximum allowed frequency of > a CPU, thanks to cpufreq_driver_resolve_freq() and internal clamping > to 'policy::max'. SchedUtil is responsible to respect that upper limit > while setting the frequency through CPUFreq drivers. This effective > frequency is stored internally in 'sugov_policy::next_freq' and EAS has > to predict that value. > > In the existing code the raw value of arch_scale_cpu_capacity() is used > for clamping the returned CPU utilization from effective_cpu_util(). > This patch fixes issue with too big single CPU utilization, by introducing > clamping to the allowed CPU capacity. The allowed CPU capacity is a CPU > capacity reduced by thermal pressure raw value. > > Thanks to knowledge about allowed CPU capacity, we don't get too big value > for a single CPU utilization, which is then added to the util sum. The > util sum is used as a source of information for estimating whole PD energy. > To avoid wrong energy estimation in EAS (due to capped frequency), make > sure that the calculation of util sum is aware of allowed CPU capacity. > > This thermal pressure might be visible in scenarios where the CPUs are not > heavily loaded, but some other component (like GPU) drastically reduced > available power budget and increased the SoC temperature. Thus, we still > use EAS for task placement and CPUs are not over-utilized. > > Signed-off-by: Lukasz Luba > Signed-off-by: Peter Zijlstra (Intel) > Reviewed-by: Vincent Guittot > Reviewed-by: Dietmar Eggemann > Link: https://lore.kernel.org/r/20210614191128.22735-1-lukasz.luba@arm.com > Signed-off-by: Sasha Levin > --- > kernel/sched/fair.c | 11 ++++++++--- > 1 file changed, 8 insertions(+), 3 deletions(-) It has been picked up automatically right? To make it fully working you need also this patch: https://lore.kernel.org/linux-pm/20210614191030.22241-1-lukasz.luba@arm.com/ It makes sure that the thermal pressure signal gets proper information also for CPUs which were offline and then wake-up. It has a proper fix tagging with commit hash id. That patch can be ported to stable: v5.6+ I can send it to stable list. Please let me know if you need any help. The same applies to patch which I found for v5.13-stable: [PATCH AUTOSEL 5.13 65/85] sched/fair: Take thermal pressure into account while estimating energy https://lore.kernel.org/stable/20210704230420.1488358-65-sashal@kernel.org/T/#u Regards, Lukasz