Received: by 2002:a05:6902:102b:0:0:0:0 with SMTP id x11csp1704463ybt; Mon, 15 Jun 2020 07:22:47 -0700 (PDT) X-Google-Smtp-Source: ABdhPJwVNd23GGK5pCOX4u+fIZ0doWSLRbjWJGSYhcfa+X24cE8ey0VmZeYmfXZbcfhm2DN+c0kt X-Received: by 2002:a17:906:7d91:: with SMTP id v17mr26266622ejo.463.1592230967664; Mon, 15 Jun 2020 07:22:47 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1592230967; cv=none; d=google.com; s=arc-20160816; b=gnA2dVFEZSPVQnP0/1ZeITVhsfxN1s4PSOH6IspgKGL0ReyEPAW9FxHEqtNtu9yrrm +fljRSo/Cz0hTfK8ScZ2nh6tJiLFjWsNe5GwQDqmC9W5mEB+l2CVB8vAv33hO4Nxa5AJ h9SHXb84CEonXw/hCiTgs3iO0ejVHDZ9H9dUCie6gscF1WAwgtNevdCRPzN9J0BvlnBu t1NFVjEkmrLJvfuN7dDAvxYq9XoDSQDObNncMt6kSvuXyTIPwfMUF8XahT4J2BFFE02O EKa37xopGe+WpQqiI784K20g2LR3W6ZoNrU6FyxKCrZVuvribXnqmSAEl1vmIFMv6GMW 0bCQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:message-id:date:subject:cc:to:from; bh=Fz/QLtdoiFq8/PkeUzptxlMtBKcMh7qRA4v/pn//9ZA=; b=OfJdZa/M2Ov4ybcIav3wSfwUzuQcpGfGK8RL/Pv++1SSAVf81KBqCeT4PO0doWlf43 YQRQRO6ItOb1/fGNvUqft97DMu5ppURURdcjPqjgEycvOBsuL6ZdXd7s4taoWeYlrEvg 37AKRglmYF9YrzNyjhNquyYCNG4zuUkhTq5ifScA3lc0VOL31Jk6donSzYFynn70VlhH T/musixbRZ7RH1RoTi+aRMj7f66bknTV3alvExapDowlAoIeFwDf67oAmaO/e9qdm31I Y7ruXRnwFgLQtGl3Vm5HFD3xEhiK5RQTdV12znL8VntPbGeQgp3FuuDOAvsboxeKGq2n xakQ== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=alibaba.com Return-Path: Received: from vger.kernel.org (vger.kernel.org. [23.128.96.18]) by mx.google.com with ESMTP id n19si8411791edv.82.2020.06.15.07.22.25; Mon, 15 Jun 2020 07:22:47 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=alibaba.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730376AbgFOOUh (ORCPT + 99 others); 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