From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S936040Ab3DJNlj (ORCPT ); Wed, 10 Apr 2013 09:41:39 -0400 Received: from terminus.zytor.com ([198.137.202.10]:59325 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759688Ab3DJNli (ORCPT ); Wed, 10 Apr 2013 09:41:38 -0400 Date: Wed, 10 Apr 2013 06:41:22 -0700 From: tip-bot for Li Zefan Message-ID: Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@kernel.org, peterz@infradead.org, tglx@linutronix.de, lizefan@huawei.com Reply-To: mingo@kernel.org, hpa@zytor.com, linux-kernel@vger.kernel.org, peterz@infradead.org, tglx@linutronix.de, lizefan@huawei.com In-Reply-To: <515536A9.5000700@huawei.com> References: <515536A9.5000700@huawei.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/core] sched/cpuacct: Remove redundant NULL checks in cpuacct_charge() Git-Commit-ID: 543bc0e76e6bb84300eaf9833edc5a481f788678 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.7 (terminus.zytor.com [127.0.0.1]); Wed, 10 Apr 2013 06:41:28 -0700 (PDT) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 543bc0e76e6bb84300eaf9833edc5a481f788678 Gitweb: http://git.kernel.org/tip/543bc0e76e6bb84300eaf9833edc5a481f788678 Author: Li Zefan AuthorDate: Fri, 29 Mar 2013 14:37:29 +0800 Committer: Ingo Molnar CommitDate: Wed, 10 Apr 2013 13:54:18 +0200 sched/cpuacct: Remove redundant NULL checks in cpuacct_charge() This is a micro optimization for the hot path. - We don't need to check if @ca is NULL in parent_ca(). - We don't need to check if @ca is NULL in the beginning of the for loop. Signed-off-by: Li Zefan Acked-by: Peter Zijlstra Link: http://lkml.kernel.org/r/515536A9.5000700@huawei.com Signed-off-by: Ingo Molnar --- kernel/sched/cpuacct.c | 6 +++++- kernel/sched/cpuacct.h | 2 +- 2 files changed, 6 insertions(+), 2 deletions(-) diff --git a/kernel/sched/cpuacct.c b/kernel/sched/cpuacct.c index 72bd971..b2aaaba 100644 --- a/kernel/sched/cpuacct.c +++ b/kernel/sched/cpuacct.c @@ -210,9 +210,13 @@ void cpuacct_charge(struct task_struct *tsk, u64 cputime) ca = task_ca(tsk); - for (; ca; ca = parent_ca(ca)) { + while (true) { u64 *cpuusage = per_cpu_ptr(ca->cpuusage, cpu); *cpuusage += cputime; + + ca = parent_ca(ca); + if (!ca) + break; } rcu_read_unlock(); diff --git a/kernel/sched/cpuacct.h b/kernel/sched/cpuacct.h index bd0409b..45c1682 100644 --- a/kernel/sched/cpuacct.h +++ b/kernel/sched/cpuacct.h @@ -36,7 +36,7 @@ static inline struct cpuacct *task_ca(struct task_struct *tsk) static inline struct cpuacct *parent_ca(struct cpuacct *ca) { - if (!ca || !ca->css.cgroup->parent) + if (!ca->css.cgroup->parent) return NULL; return cgroup_ca(ca->css.cgroup->parent); }