Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752414Ab3D0EkM (ORCPT ); Sat, 27 Apr 2013 00:40:12 -0400 Received: from oproxy12-pub.bluehost.com ([50.87.16.10]:33551 "HELO oproxy12-pub.bluehost.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1750943Ab3D0EkL (ORCPT ); Sat, 27 Apr 2013 00:40:11 -0400 Message-ID: <1367037606.7911.66.camel@Wailaba2> Subject: [PATCH v2 1/3] process cputimer is moving faster than its corresponding clock From: Olivier Langlois To: Peter Zijlstra , Ingo Molnar , Thomas Gleixner , schwidefsky@de.ibm.com, Steven Rostedt , Frederic Weisbecker Cc: KOSAKI Motohiro , LKML Date: Sat, 27 Apr 2013 00:40:06 -0400 In-Reply-To: <517AD0AE.1030404@gmail.com> References: <1365184746.874.103.camel@Wailaba2> <1365593710.30071.52.camel@laptop> <1365608911.707.65.camel@Wailaba2> <1365763837.17140.52.camel@laptop> <1365782115.17140.68.camel@laptop> <1366951210.7911.28.camel@Wailaba2> <1366957639.7911.42.camel@Wailaba2> <517AD0AE.1030404@gmail.com> Organization: Trillion01 Inc Content-Type: text/plain; charset="ISO-8859-1" X-Mailer: Evolution 3.8.1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-Identified-User: {5686:box610.bluehost.com:olivierl:trillion01.com} {sentby:smtp auth 173.178.230.31 authed with olivier@trillion01.com} Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2052 Lines: 55 Forbids the cputimer to drift ahead of its process clock by blocking its update when a tick occurs while a autoreaping task is currently in do_exit() between the call to release_task() and its final call to schedule(). Any task stats update after having called release_task() will be lost because they are added to the global process stats located in the signal struct from release_task(). Ideally, you should postpone the release_task() call after the final context switch to get all the stats added but this is more complex to achieve. In other words, this is slowing down the cputimer so it keep the same pace than the process clock but in fact, what should be done is to speed up the process clock by adding the missing stats to it. Signed-off-by: Olivier Langlois --- kernel/sched/fair.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 7a33e59..52d7b10 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -708,7 +708,15 @@ static void update_curr(struct cfs_rq *cfs_rq) trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime); cpuacct_charge(curtask, delta_exec); - account_group_exec_runtime(curtask, delta_exec); + /* + * Do not update the cputimer if the task is already released by + * release_task(). + * + * it would preferable to defer the autoreap release_task + * after the last context switch but harder to do. + */ + if (likely(curtask->sighand)) + account_group_exec_runtime(curtask, delta_exec); } account_cfs_rq_runtime(cfs_rq, delta_exec); -- 1.8.2.1 -- 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/