[Openstack-operators] [Openstack] Extreme network throughput tuning with KVM as hypervisor

Alejandro Comisario alejandro.comisario at mercadolibre.com
Sat Jan 11 19:12:27 UTC 2014

Well, its been a long time since we use nova with KVM, we got over the many
thousand vms, and still, something doesnt feel right.
We are using ubuntu 12.04 kernel 3.2.0-[40-48], tuned sysctl with lots of
parameters, and everything ... works, you can say, quite well.

But here's the deal, we have an special networking scenario that is,
EVERYTHING IS APIS, everything is throughput, no bandwidth.
Every 2x1Gb bonded compute node, doesnt get over the [200Mb/s - 400Mb/s]
but its handling hundreds of thousands requests per minute to the vms.

And once in a while, gives you the sensation that everything goes to hell,
timeouts from aplications over there, response times from apis going from
10ms to 200ms over there, 20ms delays happening between the vm ETH0 and the
VNET interface, etc.
So, since its a massive scenario to tune, we never kinda, nailedon WHERE TO
give this 1, 2 or 3 final buffer/ring/affinity tune to make everything work
from the compute side.

I know its a little awkward, but im craving, and jaunting for community
real life examples regarding "HIGH THROUGHPUT" tuning with KVM scenarios,
dark linux or if someone can help me go through configurations that might
sound weird / unnecesary / incorrect.

For those who are wondering, well ... i dont know what you have, lets start
with this.

COMPUTE NODES (99% of them, different vendors, but ...)
* 128/256 GB of ram
* 2 hexacores with HT enabled
* 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
* ubuntu 12.04 kernel 3.2.0-[40-48]
* Linux bridges,  no VLAN, no open-vswitch

I want to try to keep the networking appliances ( TOR's, AGGR, CORES ) as
out of the picture as possible.
im thinking "i hope this thread gets great, in time"

So, ready to learn as much as i can.
Thank you openstack community, as allways.

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