Re: VM issue causing high CPU loads

Re: VM issue causing high CPU loads

[Andrew Morton]

On Mon, 24 Aug 2009 16:23:22 +0200
Yohan <kernel@yohan.staff.proxad.net> wrote:

> Hi,
> 
>     Is someone have an idea for that :
> 
>         http://bugzilla.kernel.org/show_bug.cgi?id=14024
> 

Please generate a kernel profile to work out where all the CPU tie is
being spent.  Documentation/basic_profiling.txt is a starting point.

Thanks.

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Re: VM issue causing high CPU loads

[Mel Gorman]

On Mon, Aug 24, 2009 at 04:21:55PM -0700, Andrew Morton wrote:
> On Mon, 24 Aug 2009 16:23:22 +0200
> Yohan <kernel@yohan.staff.proxad.net> wrote:
> 
> > Hi,
> > 
> >     Is someone have an idea for that :
> > 
> >         http://bugzilla.kernel.org/show_bug.cgi?id=14024
> > 
> 
> Please generate a kernel profile to work out where all the CPU tie is
> being spent.  Documentation/basic_profiling.txt is a starting point.
> 

In the absense of a profile, here is a total stab in the dark. Is this a
NUMA machine? If so, is /proc/sys/vm/zone_reclaim_mode set to 1 and does
setting it to 0 help?

This is based on a relatively recent bug where malloc() could stall for
long times with large amounts of CPU usage due to useless scanning in
page reclaim.

-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab

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Re: VM issue causing high CPU loads

[Yohan]

Andrew Morton wrote:
> On Mon, 24 Aug 2009 16:23:22 +0200
> Yohan <kernel@yohan.staff.proxad.net> wrote:
>   
>> Hi,
>>
>>     Is someone have an idea for that :
>>
>>         http://bugzilla.kernel.org/show_bug.cgi?id=14024
>>     
> Please generate a kernel profile to work out where all the CPU tie is
> being spent.  Documentation/basic_profiling.txt is a starting point.
I did & post the profiles on the bugtrack
I dit it with a 2.6.31-rc7-git2 kernel
(need at least 2 week days after a reboot/drop_cache  to really show the 
bug)

Thanks

Re: VM issue causing high CPU loads

[Yohan]

Mel Gorman wrote:
> On Mon, Aug 24, 2009 at 04:21:55PM -0700, Andrew Morton wrote:
>   
>> On Mon, 24 Aug 2009 16:23:22 +0200
>> Yohan <kernel@yohan.staff.proxad.net> wrote:
>>     
>>> Hi,
>>>
>>>     Is someone have an idea for that :
>>>
>>>         http://bugzilla.kernel.org/show_bug.cgi?id=14024
>>>       
>> Please generate a kernel profile to work out where all the CPU tie is
>> being spent.  Documentation/basic_profiling.txt is a starting point.
>>     
> In the absense of a profile, here is a total stab in the dark. Is this a
> NUMA machine? 
This is a Intel(R) Xeon(R) CPU E5520 on Dell R610
> If so, is /proc/sys/vm/zone_reclaim_mode set to 1 and does
> setting it to 0 help?
>   
The value is already 0...


Thanks

Re: VM issue causing high CPU loads

[Yohan]

Andrew Morton wrote:
> On Mon, 24 Aug 2009 16:23:22 +0200
> Yohan <kernel@yohan.staff.proxad.net> wrote:
>   
>> Hi,
>>
>>     Is someone have an idea for that :
>>
>>         http://bugzilla.kernel.org/show_bug.cgi?id=14024
>>     
> Please generate a kernel profile to work out where all the CPU tie is
> being spent.  Documentation/basic_profiling.txt is a starting point.
>   
I post some new reports, it seems that the problem is in  
rpcauth_lookup_credcache ...

for information, this is an imap mail server that mounts ~10 netapp over 
~300 mountpoints..

Thanks
Yohan

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