Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932935Ab3D2TSa (ORCPT ); Mon, 29 Apr 2013 15:18:30 -0400 Received: from mail-qe0-f50.google.com ([209.85.128.50]:32985 "EHLO mail-qe0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758062Ab3D2TS2 (ORCPT ); Mon, 29 Apr 2013 15:18:28 -0400 Message-ID: <517EC781.5050600@gmail.com> Date: Mon, 29 Apr 2013 15:18:25 -0400 From: KOSAKI Motohiro User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.8; rv:17.0) Gecko/20130328 Thunderbird/17.0.5 MIME-Version: 1.0 To: linux-kernel@vger.kernel.org CC: KOSAKI Motohiro , Olivier Langlois , Martin Schwidefsky , Steven Rostedt , David Miller , Thomas Gleixner , Frederic Weisbecker , Ingo Molnar , Peter Zijlstra , kosaki.motohiro@gmail.com Subject: [PATCH 4/2] sched: task_sched_runtime introduce micro optimization References: <1367216762-3933-1-git-send-email-kosaki.motohiro@gmail.com> In-Reply-To: <1367216762-3933-1-git-send-email-kosaki.motohiro@gmail.com> Content-Type: text/plain; charset=ISO-2022-JP Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1095 Lines: 37 rq lock in task_sched_runtime() is necessary for two reasons. 1) accessing se.sum_exec_runtime is inatomic on 32bit and 2) do_task_delta_exec() require it. And then, 64bit can avoid holds rq lock when add_delta is false. Signed-off-by: KOSAKI Motohiro --- kernel/sched/core.c | 6 ++++++ 1 files changed, 6 insertions(+), 0 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index b817e6d..24ba1c6 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2657,6 +2657,12 @@ unsigned long long task_sched_runtime(struct task_struct *p, bool add_delta) struct rq *rq; u64 ns = 0; + /* Micro optimization. */ +#ifdef CONFIG_64BIT + if (!add_delta) + return p->se.sum_exec_runtime; +#endif + rq = task_rq_lock(p, &flags); ns = p->se.sum_exec_runtime; if (add_delta) -- 1.7.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/