[libvirt-users] [qemu-kvm] Network bandwidth limits via libvirt

[Romain Hardouin]

Hi all,

I try to understand why the interface bandwidth limits are not applied to my Ubuntu 12.04 VM (qemu-kvm driver) and I would need some insights.
I spawn my VM with OpenStack and when I issue a dumpxml on my domain, I can see that bandwidth limits are set:

<interface type='ethernet'>
  <mac address='02:68:b5:c6:fa:a5'/>
  <bandwidth>
    <inbound average='500' peak='500' burst='1000'/>
    <outbound average='500' peak='500'/>
  </bandwidth>
  <script path=''/>
  <target dev='tap68b5c6fa-a5'/>
  <model type='virtio'/>
  <alias name='net0'/>
  <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
</interface>

However when I send a big file with scp I don't see any limits applied to the transfer rate.

I've checked the domain log and I didn't see any qemu command line argument related to bandwidth limits.
Should I expect to see a specific argument like "bps_wr" for IO limits?
Also, should I expect to see something in particular under the cgroup directory for the qemu instance? Or do network limits are managed in another way than with cgroups?

Below some information about my hypervisor:

% virsh -V
Virsh command line tool of libvirt 1.2.2
See web site at http://libvirt.org/

Compiled with support for:
 Hypervisors: QEMU/KVM LXC UML Xen LibXL OpenVZ VMWare VirtualBox Test
 Networking: Remote Network Bridging Interface netcf Nwfilter VirtualPort
 Storage: Dir Disk Filesystem SCSI Multipath iSCSI LVM RBD Sheepdog
 Miscellaneous: Daemon Nodedev AppArmor Secrets Debug Readline Modular

qemu-kvm: 2.0.0
Kernel: 3.2.0-64-generic

Any hints will be appreciated :)

Thanks,

Romain