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=-11.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,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 5A073C433DF for ; Tue, 11 Aug 2020 16:55:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3D15F2076B for ; Tue, 11 Aug 2020 16:55:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729173AbgHKQzO (ORCPT ); Tue, 11 Aug 2020 12:55:14 -0400 Received: from foss.arm.com ([217.140.110.172]:38962 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728962AbgHKQzO (ORCPT ); Tue, 11 Aug 2020 12:55:14 -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 C9D5E31B; Tue, 11 Aug 2020 09:55:13 -0700 (PDT) Received: from [192.168.178.2] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id BCB0E3F22E; Tue, 11 Aug 2020 09:55:07 -0700 (PDT) Subject: Re: [PATCH] sched/fair: Optimize dequeue_task_fair() To: Jiang Biao , mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org Cc: rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, linux-kernel@vger.kernel.org, Jiang Biao References: <20200811084310.27130-1-benbjiang@tencent.com> From: Dietmar Eggemann Message-ID: <9a2ddb2d-4c9a-a85d-cba2-0956b6d953c0@arm.com> Date: Tue, 11 Aug 2020 18:55:05 +0200 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: <20200811084310.27130-1-benbjiang@tencent.com> 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 11/08/2020 10:43, Jiang Biao wrote: > Similar optimization as what has been done in commit, > 7d148be69e3a(sched/fair: Optimize enqueue_task_fair()) > > dequeue_task_fair jumps to dequeue_throttle label when cfs_rq_of(se) is > throttled which means that se can't be NULL. We can move the label after > the if (!se) statement and remove the if(!se) statment as se is always > NULL when reaching this point. > > Besides, trying to keep the same pattern with enqueue_task_fair can make > it more readable. > > Signed-off-by: Jiang Biao > --- > kernel/sched/fair.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 04fa8dbcfa4d..cbbeafdfa8b7 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -5618,10 +5618,10 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags) > > } > > -dequeue_throttle: > - if (!se) > - sub_nr_running(rq, 1); > + /* At this point se is NULL and we are at root level*/ > + sub_nr_running(rq, 1); > > +dequeue_throttle: > /* balance early to pull high priority tasks */ > if (unlikely(!was_sched_idle && sched_idle_rq(rq))) > rq->next_balance = jiffies; There is already a similar patch in master. 423d02e1463b - sched/fair: Optimize dequeue_task_fair() (2020-06-25 Peng Wang)