[libvirt-users] Hard limit for the cpu usage of a VM

[sethuraman subbiah]

>> 
>> I find that my version is 0.9.4.
>> 
>> [root at sbc11 ssubbiah]# virsh --version
>> 0.9.4
>> 
>> Should I do some modifications,enable options or add some patch to get the capability to set cap ? Thanks for all your help.
> 
> I found this comment in the code:
> 
>    /* If we does not know VCPU<->PID mapping or all vcpu runs in the same
>     * thread, we cannot control each vcpu. So we only modify cpu bandwidth
>     * when each vcpu has a separated thread.
> 	
> I think that means that in order to use CPU caps, you have to also use <vcpupin> to call out the host CPU pinning to be used by the guest VCPUS.
> 
> The original implementation was here, although I don't see much documentation in that patch series. https://www.redhat.com/archives/libvir-list/2011-July/msg01389.html
> 
> Wen, can you help out here?

Thanks Eric and Hi Wen. I did use <vcpupin> now . This is that part of my config xml file :

  <vcpu>3</vcpu>
  <cputune>
    <vcpupin vcpu='2' cpuset='0-2'/>
  </cputune>

This shows the vcpu affinity : 

[root at hgcc11 cloning_script]# virsh vcpuinfo rubis_ws
VCPU:           0
CPU:            2
State:          running
CPU time:       5.6s
CPU Affinity:   yyyy

VCPU:           1
CPU:            1
State:          running
CPU time:       0.1s
CPU Affinity:   yyyy

VCPU:           2
CPU:            0
State:          running
CPU time:       0.1s
CPU Affinity:   yyy-

[root at hgcc11 cloning_script]# virsh schedinfo rubis_ws
Scheduler      : posix
cpu_shares     : 1024

Still I get it as an invalid option : 

[root at hgcc11 cloning_script]# virsh schedinfo rubis_ws --set vcpu_quota=1100
Scheduler      : posix
error: invalid scheduler option: vcpu_quota=1100

If I try to add the quota option to the xml file : 

<vcpu>3</vcpu>
  <cputune>
    <vcpupin vcpu='2' cpuset='0-2'/>
    <quota>-1</quota>
  </cputune>
 
I get : 

[root at hgcc11 cloning_script]# virsh create images/rubis_ws.xml 
error: Failed to create domain from images/rubis_ws.xml
error: Unable to set cpu bandwidth quota: No such file or directory


Eventhough I am using libvirt 0.9.4, I think I am missing something.

> 
> -- 
> Eric Blake   eblake at redhat.com    +1-801-349-2682
> Libvirt virtualization library http://libvirt.org


-
Regards,
Sethuraman Subbiah

Graduate Student - NC state University
M.S in Computer Science