Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932177AbbLDLyK (ORCPT ); Fri, 4 Dec 2015 06:54:10 -0500 Received: from terminus.zytor.com ([198.137.202.10]:60064 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755465AbbLDLyG (ORCPT ); Fri, 4 Dec 2015 06:54:06 -0500 Date: Fri, 4 Dec 2015 03:53:13 -0800 From: tip-bot for Hiroshi Shimamoto Message-ID: Cc: linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, tglx@linutronix.de, efault@gmx.de, peterz@infradead.org, fweisbec@gmail.com, paulmck@linux.vnet.ibm.com, cmetcalf@ezchip.com, h-shimamoto@ct.jp.nec.com, mingo@kernel.org, hpa@zytor.com, lcapitulino@redhat.com, riel@redhat.com, cl@linux.com Reply-To: linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, efault@gmx.de, tglx@linutronix.de, peterz@infradead.org, fweisbec@gmail.com, cmetcalf@ezchip.com, paulmck@linux.vnet.ibm.com, h-shimamoto@ct.jp.nec.com, mingo@kernel.org, lcapitulino@redhat.com, hpa@zytor.com, riel@redhat.com, cl@linux.com In-Reply-To: <1447948054-28668-2-git-send-email-fweisbec@gmail.com> References: <1447948054-28668-2-git-send-email-fweisbec@gmail.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:locking/core] sched/cputime: Fix invalid gtime in proc Git-Commit-ID: 2541117b0cf79977fa11a0d6e17d61010677bd7b 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 Content-Length: 3031 Lines: 87 Commit-ID: 2541117b0cf79977fa11a0d6e17d61010677bd7b Gitweb: http://git.kernel.org/tip/2541117b0cf79977fa11a0d6e17d61010677bd7b Author: Hiroshi Shimamoto AuthorDate: Thu, 19 Nov 2015 16:47:28 +0100 Committer: Ingo Molnar CommitDate: Fri, 4 Dec 2015 10:18:49 +0100 sched/cputime: Fix invalid gtime in proc /proc/stats shows invalid gtime when the thread is running in guest. When vtime accounting is not enabled, we cannot get a valid delta. The delta is calculated with now - tsk->vtime_snap, but tsk->vtime_snap is only updated when vtime accounting is runtime enabled. This patch makes task_gtime() just return gtime without computing the buggy non-existing tickless delta when vtime accounting is not enabled. Use context_tracking_is_enabled() to check if vtime is accounting on some cpu, in which case only we need to check the tickless delta. This way we fix the gtime value regression on machines not running nohz full. The kernel config contains CONFIG_VIRT_CPU_ACCOUNTING_GEN=y and CONFIG_NO_HZ_FULL_ALL=n and boot without nohz_full. I ran and stop a busy loop in VM and see the gtime in host. Dump the 43rd field which shows the gtime in every second: # while :; do awk '{print $3" "$43}' /proc/3955/task/4014/stat; sleep 1; done S 4348 R 7064566 R 7064766 R 7064967 R 7065168 S 4759 S 4759 During running busy loop, it returns large value. After applying this patch, we can see right gtime. # while :; do awk '{print $3" "$43}' /proc/10913/task/10956/stat; sleep 1; done S 5338 R 5365 R 5465 R 5566 R 5666 S 5726 S 5726 Signed-off-by: Hiroshi Shimamoto Signed-off-by: Frederic Weisbecker Signed-off-by: Peter Zijlstra (Intel) Cc: Chris Metcalf Cc: Christoph Lameter Cc: Linus Torvalds Cc: Luiz Capitulino Cc: Mike Galbraith Cc: Paul E . McKenney Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Rik van Riel Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1447948054-28668-2-git-send-email-fweisbec@gmail.com Signed-off-by: Ingo Molnar --- kernel/sched/cputime.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c index 26a5446..05de80b 100644 --- a/kernel/sched/cputime.c +++ b/kernel/sched/cputime.c @@ -788,6 +788,9 @@ cputime_t task_gtime(struct task_struct *t) unsigned int seq; cputime_t gtime; + if (!context_tracking_is_enabled()) + return t->gtime; + do { seq = read_seqbegin(&t->vtime_seqlock); -- 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/