[libvirt] cgroup cpuset limited by default?

[Daniel P. Berrange]

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 at 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

Regards,
Daniel
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