From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754502AbbJNTH6 (ORCPT ); Wed, 14 Oct 2015 15:07:58 -0400 Received: from g2t4625.austin.hp.com ([15.73.212.76]:33438 "EHLO g2t4625.austin.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754458AbbJNTH4 (ORCPT ); Wed, 14 Oct 2015 15:07:56 -0400 From: Jason Low To: Peter Zijlstra , Ingo Molnar , Thomas Gleixner Cc: linux-kernel@vger.kernel.org, Oleg Nesterov , "Paul E. McKenney" , Frederic Weisbecker , Davidlohr Bueso , Steven Rostedt , Andrew Morton , George Spelvin , hideaki.kimura@hpe.com, terry.rudd@hpe.com, scott.norton@hpe.com, Jason Low Subject: [PATCH v2 1/4] timer: Optimize fastpath_timer_check() Date: Wed, 14 Oct 2015 12:07:53 -0700 Message-Id: <1444849677-29330-2-git-send-email-jason.low2@hp.com> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1444849677-29330-1-git-send-email-jason.low2@hp.com> References: <1444849677-29330-1-git-send-email-jason.low2@hp.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In fastpath_timer_check(), the task_cputime() function is always called to compute the utime and stime values. However, this is not necessary if there are no per-thread timers to check for. This patch modifies the code such that we compute the task_cputime values only when there are per-thread timers set. Signed-off-by: Jason Low Reviewed-by: Oleg Nesterov Reviewed-by: Frederic Weisbecker Reviewed-by: Davidlohr Bueso --- kernel/time/posix-cpu-timers.c | 11 +++-------- 1 files changed, 3 insertions(+), 8 deletions(-) diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c index 892e3da..aa4b6f4 100644 --- a/kernel/time/posix-cpu-timers.c +++ b/kernel/time/posix-cpu-timers.c @@ -1117,17 +1117,12 @@ static inline int task_cputime_expired(const struct task_cputime *sample, static inline int fastpath_timer_check(struct task_struct *tsk) { struct signal_struct *sig; - cputime_t utime, stime; - - task_cputime(tsk, &utime, &stime); if (!task_cputime_zero(&tsk->cputime_expires)) { - struct task_cputime task_sample = { - .utime = utime, - .stime = stime, - .sum_exec_runtime = tsk->se.sum_exec_runtime - }; + struct task_cputime task_sample; + task_cputime(tsk, &task_sample.utime, &task_sample.stime); + task_sample.sum_exec_runtime = tsk->se.sum_exec_runtime; if (task_cputime_expired(&task_sample, &tsk->cputime_expires)) return 1; } -- 1.7.2.5