Re: [Qemu-devel] [snabb-devel] Re: Make virtio-net.c ring size configurable?

[Stefan Hajnoczi]

On Mon, Feb 24, 2014 at 05:14:04PM +0100, Luke Gorrie wrote:
> On 24 February 2014 16:20, Stefan Hajnoczi <address@hidden> wrote:
> 
> > Do you want the 1:1 mapping to achieve best performance or just to
> > simplify the coding?
> >
> 
> We want to keep the real-time constraints on the data plane comfortable.
> 
> The question I ask myself is: How long can I buffer packets during
> processing before something is dropped?
> 
> 256 buffers can be consumed in 17 microseconds on a 10G interface.

This is a good point.  The virtio-net vring is too small at 256 buffers
for workloads that want to send/receive small packets at 10 Gbit/s line
rate.  (Minimum UDP packet size is 52 bytes!)

Michael: Luke has asked to increase the virtio-net virtqueue size.
Thoughts?

Stefan