Re: Networking latency - what to expect?

[Julian Stecklina <jsteckli@os.inf.tu-dresden.de>]

Thus spake David Mohr <damailings@mcbf.net>:

> On 2012-11-29 07:48, Julian Stecklina wrote:
>> Thus spake David Mohr <damailings@mcbf.net>:
>>
>>> * vm->vm (same host)    22k
>>
>> This number is in the same ballpark as what I am seeing on pretty
>> much
>> the same hardware.
>>
>> AFAICS, there is little you can do to the current virtio->virtio code
>> path that would make this substantially faster.
>
> Thanks for the feedback. Considering that it's better than the
> hardware network performance my main issue is actually the latency of
> communication between VMs on different hosts:
> * vm->vm (diff. hosts)   7k
>
> It is obvious that there is a lot more going on compared to same host
> communication, but only ~30% of the performance when the network
> hardware should not be slowing it down (too) much?

You are probably better of using SR-IOV NICs with PCI passthrough in
this case.

Maybe someone can comment on whether virtual interrupt delivery and
posted interrupts[1] are already usable. The first one should help in
either the virtio and SR-IOV scenarios, the latter only applies to
SR-IOV (and PCI passthrough in general).

Julian

[1] http://www.spinics.net/lists/kvm/msg82762.html