Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751583Ab1EaMbz (ORCPT ); Tue, 31 May 2011 08:31:55 -0400 Received: from hera.kernel.org ([140.211.167.34]:41647 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750818Ab1EaMbx (ORCPT ); Tue, 31 May 2011 08:31:53 -0400 Date: Tue, 31 May 2011 12:31:20 GMT From: tip-bot for Peter Zijlstra Message-ID: Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@redhat.com, markus@trippelsdorf.de, a.p.zijlstra@chello.nl, tglx@linutronix.de, mingo@elte.hu Reply-To: mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org, a.p.zijlstra@chello.nl, markus@trippelsdorf.de, tglx@linutronix.de, mingo@elte.hu In-Reply-To: <1306835745.2353.3.camel@twins> References: <1306835745.2353.3.camel@twins> To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/urgent] sched: Fix cross-cpu clock sync on remote wakeups Git-Commit-ID: f01114cb59d670e9b4f2c335930dd57db96e9360 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.3 (hera.kernel.org [127.0.0.1]); Tue, 31 May 2011 12:31:24 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1799 Lines: 45 Commit-ID: f01114cb59d670e9b4f2c335930dd57db96e9360 Gitweb: http://git.kernel.org/tip/f01114cb59d670e9b4f2c335930dd57db96e9360 Author: Peter Zijlstra AuthorDate: Tue, 31 May 2011 12:26:55 +0200 Committer: Ingo Molnar CommitDate: Tue, 31 May 2011 14:19:56 +0200 sched: Fix cross-cpu clock sync on remote wakeups Markus reported that commit 317f394160e ("sched: Move the second half of ttwu() to the remote cpu") caused some accounting funnies on his AMD Phenom II X4, such as weird 'top' results. It turns out that this is due to non-synced TSC and the queued remote wakeups stopped coupeling the two relevant cpu clocks, which leads to wakeups seeing time jumps, which in turn lead to skewed runtime stats. Add an explicit call to sched_clock_cpu() to couple the per-cpu clocks to restore the normal flow of time. Reported-and-tested-by: Markus Trippelsdorf Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/r/1306835745.2353.3.camel@twins Signed-off-by: Ingo Molnar --- kernel/sched.c | 1 + 1 files changed, 1 insertions(+), 0 deletions(-) diff --git a/kernel/sched.c b/kernel/sched.c index cbb3a0e..49cc70b 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -2600,6 +2600,7 @@ static void ttwu_queue(struct task_struct *p, int cpu) #if defined(CONFIG_SMP) if (sched_feat(TTWU_QUEUE) && cpu != smp_processor_id()) { + sched_clock_cpu(cpu); /* sync clocks x-cpu */ ttwu_queue_remote(p, cpu); return; } -- 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/