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=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 7DA9CC4361B for ; Tue, 15 Dec 2020 18:01:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3268922ADC for ; Tue, 15 Dec 2020 18:01:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729249AbgLOSAz (ORCPT ); Tue, 15 Dec 2020 13:00:55 -0500 Received: from foss.arm.com ([217.140.110.172]:55142 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725973AbgLOSAh (ORCPT ); Tue, 15 Dec 2020 13:00:37 -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 F0BE830E; Tue, 15 Dec 2020 09:59:45 -0800 (PST) Received: from [192.168.178.2] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 3F1CE3F66E; Tue, 15 Dec 2020 09:59:43 -0800 (PST) Subject: Re: [PATCH] fair/util_est: Separate util_est_dequeue() for cfs_rq_util_change To: Xuewen Yan , patrick.bellasi@arm.com, vincent.guittot@linaro.org, peterz@infradead.org Cc: mingo@redhat.com, juri.lelli@redhat.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, linux-kernel@vger.kernel.org, Xuewen.Yan@unisoc.com, xuewyan@foxmail.com References: <1607510656-22990-1-git-send-email-xuewen.yan@unisoc.com> From: Dietmar Eggemann Message-ID: Date: Tue, 15 Dec 2020 18:59:41 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <1607510656-22990-1-git-send-email-xuewen.yan@unisoc.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/12/2020 11:44, Xuewen Yan wrote: > when a task dequeued, it will update it's util, and cfs_rq_util_change > would check rq's util, if the cfs_rq->avg.util_est.enqueued is bigger > than cfs_rq->avg.util_avg, but because the cfs_rq->avg.util_est.enqueued > didn't be decreased, this would cause bigger cfs_rq_util by mistake, > as a result, cfs_rq_util_change may change freq unreasonablely. > > separate the util_est_dequeue() into util_est_dequeue() and > util_est_update(), and dequeue the _task_util_est(p) before update util. I assume this patch header needs a little more substance so that less involved folks understand the issue as well. Describing the testcase which reveals the problem would help here too. > Signed-off-by: Xuewen Yan > --- > kernel/sched/fair.c | 24 +++++++++++++++++++----- > 1 file changed, 19 insertions(+), 5 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index ae7ceba..20ecfd5 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -3946,11 +3946,9 @@ static inline bool within_margin(int value, int margin) > } > > static void > -util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p, bool task_sleep) > +util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p) Not sure why util_est_enqueue is inline and util_est_dequeue() and util_est_update() aren't? > { > - long last_ewma_diff; > struct util_est ue; You would just need a 'unsigned int enqueued' here, like in util_est_enqueue(). > - int cpu; > > if (!sched_feat(UTIL_EST)) > return; > @@ -3961,6 +3959,17 @@ static inline bool within_margin(int value, int margin) > WRITE_ONCE(cfs_rq->avg.util_est.enqueued, ue.enqueued); > > trace_sched_util_est_cfs_tp(cfs_rq); > +} > + > +static void > +util_est_update(struct cfs_rq *cfs_rq, struct task_struct *p, bool task_sleep) > +{ > + long last_ewma_diff; > + struct util_est ue; > + int cpu; Nitpick: 'int cpu' not needed ---8<--- diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index c3685a743a76..53dfb20d101e 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3956,28 +3956,28 @@ static inline bool within_margin(int value, int margin) return ((unsigned int)(value + margin - 1) < (2 * margin - 1)); } -static void -util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p) +static inline void util_est_dequeue(struct cfs_rq *cfs_rq, + struct task_struct *p) { - struct util_est ue; + unsigned int enqueued; if (!sched_feat(UTIL_EST)) return; /* Update root cfs_rq's estimated utilization */ - ue.enqueued = cfs_rq->avg.util_est.enqueued; - ue.enqueued -= min_t(unsigned int, ue.enqueued, _task_util_est(p)); - WRITE_ONCE(cfs_rq->avg.util_est.enqueued, ue.enqueued); + enqueued = cfs_rq->avg.util_est.enqueued; + enqueued -= min_t(unsigned int, enqueued, _task_util_est(p)); + WRITE_ONCE(cfs_rq->avg.util_est.enqueued, enqueued); trace_sched_util_est_cfs_tp(cfs_rq); } -static void -util_est_update(struct cfs_rq *cfs_rq, struct task_struct *p, bool task_sleep) +static inline void util_est_update(struct cfs_rq *cfs_rq, + struct task_struct *p, + bool task_sleep) { long last_ewma_diff; struct util_est ue; - int cpu; if (!sched_feat(UTIL_EST)) return; @@ -4021,8 +4021,7 @@ util_est_update(struct cfs_rq *cfs_rq, struct task_struct *p, bool task_sleep) * To avoid overestimation of actual task utilization, skip updates if * we cannot grant there is idle time in this CPU. */ - cpu = cpu_of(rq_of(cfs_rq)); - if (task_util(p) > capacity_orig_of(cpu)) + if (task_util(p) > capacity_orig_of(cpu_of(rq_of(cfs_rq)))) return; /* -- 2.17.1