From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752382AbbJOJ3J (ORCPT ); Thu, 15 Oct 2015 05:29:09 -0400 Received: from terminus.zytor.com ([198.137.202.10]:46202 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752290AbbJOJ3D (ORCPT ); Thu, 15 Oct 2015 05:29:03 -0400 Date: Thu, 15 Oct 2015 02:28:03 -0700 From: tip-bot for Jason Low Message-ID: Cc: peterz@infradead.org, fweisbec@gmail.com, linux@horizon.com, hpa@zytor.com, oleg@redhat.com, mingo@kernel.org, linux-kernel@vger.kernel.org, rostedt@goodmis.org, tglx@linutronix.de, paulmck@linux.vnet.ibm.com, jason.low2@hp.com, dave@stgolabs.net Reply-To: paulmck@linux.vnet.ibm.com, dave@stgolabs.net, jason.low2@hp.com, tglx@linutronix.de, linux-kernel@vger.kernel.org, rostedt@goodmis.org, hpa@zytor.com, mingo@kernel.org, oleg@redhat.com, fweisbec@gmail.com, peterz@infradead.org, linux@horizon.com In-Reply-To: <1444849677-29330-3-git-send-email-jason.low2@hp.com> References: <1444849677-29330-3-git-send-email-jason.low2@hp.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:timers/core] posix_cpu_timer: Check thread timers only when there are active thread timers Git-Commit-ID: 934715a191e4be0c602d39455a7a74316f274d60 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 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 934715a191e4be0c602d39455a7a74316f274d60 Gitweb: http://git.kernel.org/tip/934715a191e4be0c602d39455a7a74316f274d60 Author: Jason Low AuthorDate: Wed, 14 Oct 2015 12:07:54 -0700 Committer: Thomas Gleixner CommitDate: Thu, 15 Oct 2015 11:23:41 +0200 posix_cpu_timer: Check thread timers only when there are active thread timers The fastpath_timer_check() contains logic to check for if any timers are set by checking if !task_cputime_zero(). Similarly, we can do this before calling check_thread_timers(). In the case where there are only process-wide timers, this will skip all of the computations for per-thread timers when there are no per-thread timers. As suggested by George, we can put the task_cputime_zero() check in check_thread_timers(), since that is more of an optization to the function. Similarly, we move the existing check of cputimer->running to check_process_timers(). Signed-off-by: Jason Low Reviewed-by: Oleg Nesterov Reviewed-by: George Spelvin Cc: Paul E. McKenney Cc: Frederic Weisbecker Cc: Davidlohr Bueso Cc: Steven Rostedt Cc: hideaki.kimura@hpe.com Cc: terry.rudd@hpe.com Cc: scott.norton@hpe.com Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/1444849677-29330-3-git-send-email-jason.low2@hp.com Signed-off-by: Thomas Gleixner --- kernel/time/posix-cpu-timers.c | 22 ++++++++++++++++------ 1 file changed, 16 insertions(+), 6 deletions(-) diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c index aa4b6f4..6f6e252 100644 --- a/kernel/time/posix-cpu-timers.c +++ b/kernel/time/posix-cpu-timers.c @@ -864,6 +864,13 @@ static void check_thread_timers(struct task_struct *tsk, unsigned long long expires; unsigned long soft; + /* + * If cputime_expires is zero, then there are no active + * per thread CPU timers. + */ + if (task_cputime_zero(&tsk->cputime_expires)) + return; + expires = check_timers_list(timers, firing, prof_ticks(tsk)); tsk_expires->prof_exp = expires_to_cputime(expires); @@ -962,6 +969,13 @@ static void check_process_timers(struct task_struct *tsk, unsigned long soft; /* + * If cputimer is not running, then there are no active + * process wide timers (POSIX 1.b, itimers, RLIMIT_CPU). + */ + if (!READ_ONCE(tsk->signal->cputimer.running)) + return; + + /* * Collect the current process totals. */ thread_group_cputimer(tsk, &cputime); @@ -1169,12 +1183,8 @@ void run_posix_cpu_timers(struct task_struct *tsk) * put them on the firing list. */ check_thread_timers(tsk, &firing); - /* - * If there are any active process wide timers (POSIX 1.b, itimers, - * RLIMIT_CPU) cputimer must be running. - */ - if (READ_ONCE(tsk->signal->cputimer.running)) - check_process_timers(tsk, &firing); + + check_process_timers(tsk, &firing); /* * We must release these locks before taking any timer's lock.