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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 60676C4338F for ; Wed, 11 Aug 2021 11:49:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3BE5E60C3E for ; Wed, 11 Aug 2021 11:49:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237315AbhHKLuS (ORCPT ); Wed, 11 Aug 2021 07:50:18 -0400 Received: from mx313.baidu.com ([180.101.52.140]:21300 "EHLO njjs-sys-mailin07.njjs.baidu.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S236777AbhHKLuO (ORCPT ); Wed, 11 Aug 2021 07:50:14 -0400 Received: from unknown.domain.tld (bjhw-sys-rpm015653cc5.bjhw.baidu.com [10.227.53.39]) by njjs-sys-mailin07.njjs.baidu.com (Postfix) with ESMTP id 3F9E019480056; Wed, 11 Aug 2021 19:49:47 +0800 (CST) From: Li RongQing To: mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, linux-kernel@vger.kernel.org Subject: [PATCH] sched/fair: micro-optimize pick_next_entity() Date: Wed, 11 Aug 2021 19:48:02 +0800 Message-Id: <20210811114802.7408-1-lirongqing@baidu.com> X-Mailer: git-send-email 2.9.4 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org only check the skip buddy when next buddy and last buddy are not picked up, this can save the cycles of checking the skip buddy and compute the second buddy when next and last buddy will be picked up Signed-off-by: Li RongQing --- kernel/sched/fair.c | 33 ++++++++++++++++----------------- 1 file changed, 16 insertions(+), 17 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 44c4520..9c6569dd 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4503,11 +4503,22 @@ pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr) se = left; /* ideally we run the leftmost entity */ - /* - * Avoid running the skip buddy, if running something else can - * be done without getting too unfair. - */ - if (cfs_rq->skip && cfs_rq->skip == se) { + + if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1) { + /* + * Someone really wants this to run. If it's not unfair, run it. + */ + se = cfs_rq->next; + } else if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1) { + /* + * Prefer last buddy, try to return the CPU to a preempted task. + */ + se = cfs_rq->last; + } else if (cfs_rq->skip && cfs_rq->skip == se) { + /* + * Avoid running the skip buddy, if running something else can + * be done without getting too unfair. + */ struct sched_entity *second; if (se == curr) { @@ -4522,18 +4533,6 @@ pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr) se = second; } - if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1) { - /* - * Someone really wants this to run. If it's not unfair, run it. - */ - se = cfs_rq->next; - } else if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1) { - /* - * Prefer last buddy, try to return the CPU to a preempted task. - */ - se = cfs_rq->last; - } - return se; } -- 2.9.4