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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 79FCBC4167B for ; Thu, 30 Nov 2023 20:30:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231901AbjK3UaB (ORCPT ); Thu, 30 Nov 2023 15:30:01 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34580 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229493AbjK3UaA (ORCPT ); Thu, 30 Nov 2023 15:30:00 -0500 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id AD73E1703; Thu, 30 Nov 2023 12:30:05 -0800 (PST) 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 30A2C1042; Thu, 30 Nov 2023 12:30:52 -0800 (PST) Received: from [10.57.82.136] (unknown [10.57.82.136]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 7D6A03F73F; Thu, 30 Nov 2023 12:30:02 -0800 (PST) Message-ID: <8009d5c4-4012-44a2-883c-0d7f74c4a2c1@arm.com> Date: Thu, 30 Nov 2023 20:30:01 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] sched/fair: Remove SCHED_FEAT(UTIL_EST_FASTUP, true) Content-Language: en-US To: Vincent Guittot , mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, corbet@lwn.net, alexs@kernel.org, siyanteng@loongson.cn, qyousef@layalina.io, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org Cc: lukasz.luba@arm.com References: <20231127143238.1216582-1-vincent.guittot@linaro.org> <20231127143238.1216582-2-vincent.guittot@linaro.org> From: Hongyan Xia In-Reply-To: <20231127143238.1216582-2-vincent.guittot@linaro.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 27/11/2023 14:32, Vincent Guittot wrote: > sched_feat(UTIL_EST_FASTUP) has been added to easily disable the feature > in order to check for possibly related regressions. After 3 years, it has > never been used and no regression has been reported. Let remove it > and make fast increase a permanent behavior. > > Signed-off-by: Vincent Guittot > --- > > I haven't updated the chinese documentation which also refers to > UTIL_EST_FASTUP. IIUC, this will be updated afterward by the > Translations' maintainers. Here it is in case you have to provide the translation: diff --git a/Documentation/translations/zh_CN/scheduler/schedutil.rst b/Documentation/translations/zh_CN/scheduler/schedutil.rst index d1ea68007520..7c8d87f21c42 100644 --- a/Documentation/translations/zh_CN/scheduler/schedutil.rst +++ b/Documentation/translations/zh_CN/scheduler/schedutil.rst @@ -89,16 +89,15 @@ r_cpu被定义为当前CPU的最高性能水平与系统中任何其它CPU的最 - Documentation/translations/zh_CN/scheduler/sched-capacity.rst:"1. CPU Capacity + 2. Task utilization" -UTIL_EST / UTIL_EST_FASTUP -========================== +UTIL_EST +======== 由于周期性任务的平均数在睡眠时会衰减，而在运行时其预期利用率会和睡眠前相同， 因此它们在再次运行后会面临（DVFS）的上涨。 为了缓解这个问题，（一个默认使能的编译选项）UTIL_EST驱动一个无限脉冲响应 （Infinite Impulse Response，IIR）的EWMA，“运行”值在出队时是最高的。 -另一个默认使能的编译选项UTIL_EST_FASTUP修改了IIR滤波器，使其允许立即增加， -仅在利用率下降时衰减。 +UTIL_EST滤波使其在遇到更高值时立刻增加，而遇到低值时会缓慢衰减。 进一步，运行队列的（可运行任务的）利用率之和由下式计算： > > Documentation/scheduler/schedutil.rst | 7 +++---- > kernel/sched/fair.c | 8 +++----- > kernel/sched/features.h | 1 - > 3 files changed, 6 insertions(+), 10 deletions(-) > > diff --git a/Documentation/scheduler/schedutil.rst b/Documentation/scheduler/schedutil.rst > index 32c7d69fc86c..803fba8fc714 100644 > --- a/Documentation/scheduler/schedutil.rst > +++ b/Documentation/scheduler/schedutil.rst > @@ -90,8 +90,8 @@ For more detail see: > - Documentation/scheduler/sched-capacity.rst:"1. CPU Capacity + 2. Task utilization" > > > -UTIL_EST / UTIL_EST_FASTUP > -========================== > +UTIL_EST > +======== > > Because periodic tasks have their averages decayed while they sleep, even > though when running their expected utilization will be the same, they suffer a > @@ -99,8 +99,7 @@ though when running their expected utilization will be the same, they suffer a > > To alleviate this (a default enabled option) UTIL_EST drives an Infinite > Impulse Response (IIR) EWMA with the 'running' value on dequeue -- when it is > -highest. A further default enabled option UTIL_EST_FASTUP modifies the IIR > -filter to instantly increase and only decay on decrease. > +highest. UTIL_EST filters to instantly increase and only decay on decrease. > > A further runqueue wide sum (of runnable tasks) is maintained of: > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 34fe6e9490c2..146329678cb8 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -4870,11 +4870,9 @@ static inline void util_est_update(struct cfs_rq *cfs_rq, > * to smooth utilization decreases. > */ > ue.enqueued = task_util(p); > - if (sched_feat(UTIL_EST_FASTUP)) { > - if (ue.ewma < ue.enqueued) { > - ue.ewma = ue.enqueued; > - goto done; > - } > + if (ue.ewma < ue.enqueued) { > + ue.ewma = ue.enqueued; > + goto done; > } > > /* > diff --git a/kernel/sched/features.h b/kernel/sched/features.h > index a3ddf84de430..143f55df890b 100644 > --- a/kernel/sched/features.h > +++ b/kernel/sched/features.h > @@ -83,7 +83,6 @@ SCHED_FEAT(WA_BIAS, true) > * UtilEstimation. Use estimated CPU utilization. > */ > SCHED_FEAT(UTIL_EST, true) > -SCHED_FEAT(UTIL_EST_FASTUP, true) > > SCHED_FEAT(LATENCY_WARN, false) > Reviewed-by: Hongyan Xia