From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754122Ab2GRLxE (ORCPT ); Wed, 18 Jul 2012 07:53:04 -0400 Received: from e06smtp18.uk.ibm.com ([195.75.94.114]:32855 "EHLO e06smtp18.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751853Ab2GRLxC (ORCPT ); Wed, 18 Jul 2012 07:53:02 -0400 Date: Wed, 18 Jul 2012 13:52:55 +0200 From: Martin Schwidefsky To: "Srivatsa S. Bhat" Cc: Michal Hocko , Thomas Gleixner , linux-kernel Subject: Re: [PATCH v2] fix idle ticks in cpu summary line of /proc/stat Message-ID: <20120718135255.1eafb680@de.ibm.com> In-Reply-To: <4F5F0623.6080702@linux.vnet.ibm.com> References: <20120311182621.41674b39@de.ibm.com> <20120312121726.GA23608@tiehlicka.suse.cz> <20120312101739.26eb373e@de.ibm.com> <4F5E0CC1.6010102@linux.vnet.ibm.com> <20120312153906.GE3994@tiehlicka.suse.cz> <20120312164145.5110ed5c@de.ibm.com> <20120313080748.GA7754@tiehlicka.suse.cz> <4F5F0623.6080702@linux.vnet.ibm.com> Organization: IBM Corporation X-Mailer: Claws Mail 3.8.1 (GTK+ 2.24.10; i486-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit x-cbid: 12071811-6892-0000-0000-00000277E389 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 13 Mar 2012 14:02:35 +0530 "Srivatsa S. Bhat" wrote: > On 03/13/2012 01:37 PM, Michal Hocko wrote: > > > OK, so the updated version of the patch looks like this. I am sorry but > > I had time to only compile test this... > > --- > > From d12247f14c5f8b00ae97a87442f62e49227a759b Mon Sep 17 00:00:00 2001 > > From: Michal Hocko > > Date: Mon, 12 Mar 2012 13:11:38 +0100 > > Subject: [PATCH] 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. > > > > Cc: Thomas Gleixner > > Cc: "Srivatsa S. Bhat" > > Reported-by: Martin Schwidefsky > > Signed-off-by: Michal Hocko > > --- > > 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 121f77c..62bda24 100644 > > --- a/fs/proc/stat.c > > +++ b/fs/proc/stat.c > > @@ -24,10 +24,13 @@ > > > > 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]; > > idle += arch_idle_time(cpu); > > } else > > @@ -38,10 +41,13 @@ 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); > > > > Yeah, this looks much better.. > > Reviewed-by: Srivatsa S. Bhat What happened to this patch? The fix for s390 (git commit cb85a6ed67e979c59 "proc: stats: Use arch_idle_time for idle and iowait times if available" is upstream but the fix for non-s390 systems is missing, no? -- blue skies, Martin. "Reality continues to ruin my life." - Calvin.