[libvirt-users] Permission issue with cgroups

Eric Blake eblake at redhat.com
Fri May 11 22:04:52 UTC 2012

On 05/11/2012 03:51 PM, Antonio Carlos Salzvedel Furtado Junior wrote:
> Thanks for the prompt response, it cleared a lot of my doubts
> Actually, I could enable the other controllers. It's just that I have a
> strong reason to use the cpu controller.
> I need to set a hard limit for CPU consumption. Maybe 'cpu.shares' was a
> bad example.
> I'm working especially with two parameters, "cpu.cfs_period_us" and
> "cpu.cfs_quota_us". For instance, sometimes I need to limit my VM to 20% of
> the CPU share, regardless of the CPU load. Then I set
> "cpu.cfs_period_us=100000" and "cpu.cfs_quota_us=20000".
> I'm using the libcgroup API to do that, but I agree that it would be better
> to use the libvirt API.
> Looking at the documentation, The parameters I'd need to change would be
> the following:
> <domain>
>   ...
>   <cputune>
>     <period>100000</period>
>     <quota>20000</quota>
>   </cputune>
>   ...
> </domain>
> Unfortunately, I think virsh does not have tools to change these
> parameters, as libcgroup does ( cgget and cgset ). However I guess it won't
> be a problem, I'll try to use the libvirt API.

virsh exposes the libvirt API; if you can't get it working in virsh,
that's a bug that we should fix.  That said:

virsh schedinfo $dom --set vcpu_period=100000 --set vcpu_quota=20000

should do exactly what you're asking for.

Eric Blake   eblake at redhat.com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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