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| author | Michal Hocko <mhocko@suse.cz> | 2012-10-10 11:51:09 +0530 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2012-10-10 14:05:21 +0200 |
| commit | 7386cdbf2f57ea8cff3c9fde93f206e58b9fe13f (patch) | |
| tree | 8ae7decceaeb1a453e167828bfaec1771a059cc3 /lib/cpu_rmap.c | |
| parent | f784e8a7989c0da3062d04bfea3db90f41e8f738 (diff) | |
| download | blackbird-op-linux-7386cdbf2f57ea8cff3c9fde93f206e58b9fe13f.tar.gz blackbird-op-linux-7386cdbf2f57ea8cff3c9fde93f206e58b9fe13f.zip | |
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 <schwidefsky@de.ibm.com>
Signed-off-by: Michal Hocko <mhocko@suse.cz>
Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
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 <tglx@linutronix.de>
Diffstat (limited to 'lib/cpu_rmap.c')
0 files changed, 0 insertions, 0 deletions
