Re: [Qemu-discuss] Throttle in virtio-net

[Pradeep Kiruvale]

Hi Alberto,

Thanks for your reply.

> I am planning to implement throttling functionality for virtio-net
> driver using the throttling APIs that exist inside qemu.

Hi Pradeep,

the problem with implementing throttling for the network is that
it's useless if you use the vhost_net kernel accelerator, because it
bypasses QEMU entirely:

   https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/Virtualization_Tuning_and_Optimization_Guide/sect-Virtualization_Tuning_Optimization_Guide-Networking-Virtio_and_vhostnet.html

Thanks for this very valuable information. What if someone wants to just use virtio-net without the vhost acceleration? 

Any idea how it will be done in this case? It still uses cgroup or some other mechanism to do throttling?

libvirt implements this using tc:

   https://libvirt.org/formatdomain.html#elementDomain
   http://luxik.cdi.cz/~devik/qos/htb/manual/userg.htm#ceiling

Here it uses the cgroup inside the libvirt dirver to control the packet rate right?  

Thanks,

Pradeep