[Qemu-devel] Throttle in virtio-net

[Qemu-devel] Throttle in virtio-net

[Pradeep Kiruvale]

Hi All,

I am planning to implement throttling functionality for virtio-net driver
using the throttling APIs that exist inside qemu.
Please let me know if someone already working on the same. Asking because I
do not want to just replicate the work.

Thanks & Regards,
Pradeep

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

[Alberto Garcia]

On Fri, Sep 02, 2016 at 05:13:40PM +0200, Pradeep Kiruvale wrote:

> 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

libvirt implements this using tc:

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

Berto

Re: [Qemu-devel] [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

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

[Alberto Garcia]

On Mon 05 Sep 2016 10:52:40 AM CEST, Pradeep Kiruvale wrote:

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

I think you can use tc just the same, as far as I'm aware that's what
libvirt does.

Berto

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

[Daniel P. Berrange]

On Mon, Sep 05, 2016 at 10:52:40AM +0200, Pradeep Kiruvale wrote:
> 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?

No, cgroups is not involved. Libvirt attaches a tc filter directly to
the host TAP device associated with the virtual NIC.

Cgroups tc support would only be relevant if you're trying to filter
non-NIC related network traffic QEMU generates.

Regards,
Daniel
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