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=-9.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, UNPARSEABLE_RELAY,USER_AGENT_GIT 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 8D6D8C433E0 for ; Mon, 15 Jun 2020 14:20:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 722582067B for ; Mon, 15 Jun 2020 14:20:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730520AbgFOOUh (ORCPT ); Mon, 15 Jun 2020 10:20:37 -0400 Received: from out30-56.freemail.mail.aliyun.com ([115.124.30.56]:59686 "EHLO out30-56.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729733AbgFOOUh (ORCPT ); Mon, 15 Jun 2020 10:20:37 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R871e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01f04427;MF=rocking@linux.alibaba.com;NM=1;PH=DS;RN=9;SR=0;TI=SMTPD_---0U.foqgV_1592230772; Received: from localhost(mailfrom:rocking@linux.alibaba.com fp:SMTPD_---0U.foqgV_1592230772) by smtp.aliyun-inc.com(127.0.0.1); Mon, 15 Jun 2020 22:20:33 +0800 From: Peng Wang To: mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de Cc: linux-kernel@vger.kernel.org Subject: [PATCH] sched/fair: Optimize dequeue_task_fair() Date: Mon, 15 Jun 2020 22:16:16 +0800 Message-Id: <6f2f195aea48bc50187dfb064aa530ba132be01b.1592230286.git.rocking@linux.alibaba.com> X-Mailer: git-send-email 2.9.5 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org While looking at enqueue_task_fair and dequeue_task_fair, it occurred to me that dequeue_task_fair can also be optimized as Vincent described in commit 7d148be69e3a ("sched/fair: Optimize enqueue_task_fair()"). dequeue_throttle label can ensure se not to be NULL, and se is always NULL when reaching root level. Signed-off-by: Peng Wang --- 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 cbcb2f7..e6be952 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5614,10 +5614,10 @@ 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; -- 2.9.5