Messages in this thread | | | Date | Thu, 29 Mar 2012 12:42:22 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [PATCH v2] fix idle ticks in cpu summary line of /proc/stat |
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On Tue, 13 Mar 2012, 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 <mhocko@suse.cz> > 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 <tglx@linutronix.de> > Cc: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com> > Reported-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Martin, does that solve the problem for you ?
Thanks,
tglx
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