Open Stack

Hi guys, we had in the past when using physical servers, several throughput
issues regarding the throughput of our APIS, in our case we measure this
with packets per seconds, since we dont have that much bandwidth (Mb/s)
since our apis respond lots of packets very small ones (maximum response of
3.5k and avg response of 1.5k), when we where using this physical servers,
when we reach throughput capacity (due to clients tiemouts) we touched the
ethernet ring configuration and we made the problem dissapear.

Today with kvm and over 10k virtual instances, when we want to increase the
throughput of KVM instances, we bumped with the fact that when using virtio
on guests, we have a max configuration of the ring of 256 TX/RX, and from
the host side the atached vnet has a txqueuelen of 500.

What i want to know is, how can i tune the guest to support more packets
per seccond if i know that's my bottleneck?

* does virtio exposes more packets to configure in the virtual ethernet's
ring ?
* does the use of vhost_net helps me with increasing packets per second and
not only bandwidth?

does anyone has to struggle with this before and knows where i can look
into ?
there's LOOOOOOOOOOOOOOOTS of information about networking performance
tuning of kvm, but nothing related to increase throughput in pps capacity.

This is a couple of configurations that we are having right now on the
compute nodes:

* 2x1Gb bonded interfaces (want to know the more than 20 models we are
using, just ask for it)
* Multi queue interfaces, pined via irq to different cores
* Linux bridges,  no VLAN, no open-vswitch
* ubuntu 12.04 kernel 3.2.0-[40-48]


any help will be incredibly apreciated !!

thank you.
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