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Re: [libvirt] cgroup cpuset limited by default?



On 04/17/2012 03:02 PM, Daniel P. Berrange wrote:

> On Tue, Apr 17, 2012 at 11:09:33AM +0530, Srivatsa S. Bhat wrote:
>> On 04/16/2012 09:43 PM, Daniel P. Berrange wrote:
>>
>>> On Mon, Apr 16, 2012 at 06:00:22PM +0200, Marc-André Lureau wrote:
>>>> Hi
>>>>
>>>> On Mon, Apr 16, 2012 at 2:32 PM, Srivatsa S. Bhat
>>>> <srivatsa bhat linux vnet ibm com> wrote:
>>>>> On 04/16/2012 05:34 PM, Marc-André Lureau wrote:
>>>>> Did you happen to perform a suspend/resume or a hibernation/restore
>>>>> on your computer? (Or did you do CPU hotplug manually?)
>>>>>
>>>>> If yes, you might be seeing the problem reported at:
>>>>> https://bugzilla.redhat.com/show_bug.cgi?id=714271
>>>>
>>>> yep, thank you very much, that seems to be the reason
>>
>>
>> Thanks for the confirmation. The script below might work as a
>> temporary workaround.
>>
>>>
>>> This problem has existed for ages now. I wonder if there's a way we get get
>>> a userspace workaround implemented.
>>>
>>> IIRC, pm-utils has the ability to run arbitrary shell scripts upon
>>> restore from suspend/hibernate. We could put a temp hack in libvirt
>>> which resets the CPU affinity in the top level libvirt cgroup. That
>>> would at least make new VMs start with good affinity. To deal with
>>> existing running VMs, we would need to record existing affinity
>>> before suspend & re-store it fully afterwards which is more complicated
>>>
>>
>>
>> I don't think that would be all that complicated.. Below is a script
>> that should do the trick, for all cases, including existing running VMs.
>>
>> This script is not at all specific to libvirt by the way (as the problem
>> itself is not at all libvirt specific). It saves the cpuset configuration
>> before suspend and restores it after resume, for all cpusets (not only
>> the ones controlled by libvirt). Of course, it hooks onto the pm-utils
>> mechanism, as you mentioned.
> 
> Thanks for taking the time to write this. I have opened a BZ against
> systemd to see if they are willing to ship this script as a standard
> workaround for the kernel bug, since they are responsible for mounting
> the cpuset cgroups in Fedora 16 and later
> 
>   https://bugzilla.redhat.com/show_bug.cgi?id=813228
> 


Nice! Thanks :-)

Regards,
Srivatsa S. Bhat
IBM Linux Technology Center


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