From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753828Ab2JJMO3 (ORCPT ); Wed, 10 Oct 2012 08:14:29 -0400 Received: from terminus.zytor.com ([198.137.202.10]:49862 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753344Ab2JJMO1 (ORCPT ); Wed, 10 Oct 2012 08:14:27 -0400 Date: Wed, 10 Oct 2012 05:14:02 -0700 From: tip-bot for Michal Hocko Message-ID: Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@kernel.org, schwidefsky@de.ibm.com, srivatsa.bhat@linux.vnet.ibm.com, tglx@linutronix.de, mhocko@suse.cz Reply-To: mingo@kernel.org, hpa@zytor.com, linux-kernel@vger.kernel.org, schwidefsky@de.ibm.com, tglx@linutronix.de, srivatsa.bhat@linux.vnet.ibm.com, mhocko@suse.cz In-Reply-To: <20121010061820.8999.57245.stgit@srivatsabhat.in.ibm.com> References: <20121010061820.8999.57245.stgit@srivatsabhat.in.ibm.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:core/urgent] nohz: Fix idle ticks in cpu summary line of / proc/stat Git-Commit-ID: 7386cdbf2f57ea8cff3c9fde93f206e58b9fe13f 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 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.6 (terminus.zytor.com [127.0.0.1]); Wed, 10 Oct 2012 05:14:08 -0700 (PDT) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 7386cdbf2f57ea8cff3c9fde93f206e58b9fe13f Gitweb: http://git.kernel.org/tip/7386cdbf2f57ea8cff3c9fde93f206e58b9fe13f Author: Michal Hocko AuthorDate: Wed, 10 Oct 2012 11:51:09 +0530 Committer: Thomas Gleixner CommitDate: Wed, 10 Oct 2012 14:05:21 +0200 nohz: Fix idle ticks in cpu summary line of /proc/stat Git commit 09a1d34f8535ecf9 "nohz: Make idle/iowait counter update conditional" introduced a bug in regard to cpu hotplug. The effect is that the number of idle ticks in the cpu summary line in /proc/stat is still counting ticks for offline cpus. Reproduction is easy, just start a workload that keeps all cpus busy, switch off one or more cpus and then watch the idle field in top. On a dual-core with one cpu 100% busy and one offline cpu you will get something like this: %Cpu(s): 48.7 us, 1.3 sy, 0.0 ni, 50.0 id, 0.0 wa, 0.0 hi, 0.0 si, %0.0 st The problem is that an offline cpu still has ts->idle_active == 1. To fix this we should make sure that the cpu is online when calling get_cpu_idle_time_us and get_cpu_iowait_time_us. [Srivatsa: Rebased to current mainline] Reported-by: Martin Schwidefsky Signed-off-by: Michal Hocko Reviewed-by: Srivatsa S. Bhat Signed-off-by: Srivatsa S. Bhat Link: http://lkml.kernel.org/r/20121010061820.8999.57245.stgit@srivatsabhat.in.ibm.com Cc: deepthi@linux.vnet.ibm.com Cc: stable@vger.kernel.org Signed-off-by: Thomas Gleixner --- fs/proc/stat.c | 14 ++++++++++---- 1 files changed, 10 insertions(+), 4 deletions(-) diff --git a/fs/proc/stat.c b/fs/proc/stat.c index 64c3b31..e296572 100644 --- a/fs/proc/stat.c +++ b/fs/proc/stat.c @@ -45,10 +45,13 @@ static cputime64_t get_iowait_time(int cpu) static u64 get_idle_time(int cpu) { - u64 idle, idle_time = get_cpu_idle_time_us(cpu, NULL); + u64 idle, idle_time = -1ULL; + + if (cpu_online(cpu)) + idle_time = get_cpu_idle_time_us(cpu, NULL); if (idle_time == -1ULL) - /* !NO_HZ so we can rely on cpustat.idle */ + /* !NO_HZ or cpu offline so we can rely on cpustat.idle */ idle = kcpustat_cpu(cpu).cpustat[CPUTIME_IDLE]; else idle = usecs_to_cputime64(idle_time); @@ -58,10 +61,13 @@ static u64 get_idle_time(int cpu) static u64 get_iowait_time(int cpu) { - u64 iowait, iowait_time = get_cpu_iowait_time_us(cpu, NULL); + u64 iowait, iowait_time = -1ULL; + + if (cpu_online(cpu)) + iowait_time = get_cpu_iowait_time_us(cpu, NULL); if (iowait_time == -1ULL) - /* !NO_HZ so we can rely on cpustat.iowait */ + /* !NO_HZ or cpu offline so we can rely on cpustat.iowait */ iowait = kcpustat_cpu(cpu).cpustat[CPUTIME_IOWAIT]; else iowait = usecs_to_cputime64(iowait_time);