On 27 February 2014 15:49, Michael S. Tsirkin <m...@redhat.com> wrote:

> > Michael: Luke has asked to increase the virtio-net virtqueue size.
> > Thoughts?
> >
> > Stefan
>
> Heh you want to increase the bufferbloat?
>

I'm sensitive to this. (I have actually built a commercial anti-bufferbloat
network device for ISPs in the recent past.) I will go to great lengths to
keep latency below 1 millisecond but beyond that I'm more flexible.

Each buffer pointer takes up 16 bytes so we are using order-2
> allocations as it is, anything more and it'll start to fail
> if hotplug happens long after boot.
>

(Sorry I don't have the background to understand this issue.)


> AFAIK baremetal does not push line rate with 1 byte payload
> either.
>

To me it feels normal to do this in the commercial networking industry.
Many networking vendors will sell you a NIC with a software interface to
drive it at line rate from userspace: Intel, Myricom, SolarFlare, Chelsio,
Mellanox. They really work. Lots of high-end commercial network devices are
built on these simple and cheap components.

Here's one detailed performance test that Luca Deri did based on standard
Intel CPU and NIC and all packet sizes:
http://www.ntop.org/wp-content/uploads/2012/04/DNA_ip_forward_RFC2544.pdf

For my project now I need to drive 6x10G ports worth of network traffic
through Virtio-net to KVM guests. That's the ballpark of what ISPs I'm
talking with require to be able to use Virtio-net instead of
SR-IOV+Passthrough. They really want to use Virtio-net for a variety of
reasons and the only barrier is performance for router-like workloads.

I'm working on Deutsche Telekom's TeraStream project [1] [2] and success
will mean that Virtio-net drives all internet traffic for national ISPs.
That would be really cool imo :-).

[1] TeraStream blurb
http://blog.ipspace.net/2013/11/deutsche-telekom-terastream-designed.html
[2] TeraStream talk http://ripe67.ripe.net/archives/video/3/

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