lkml.org 
[lkml]   [2012]   [Mar]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v2] fix idle ticks in cpu summary line of /proc/stat
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


\
 
 \ /
  Last update: 2012-03-29 12:45    [W:0.094 / U:0.032 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site