[FreeBSD 8.2 amd64 XENHVM] DomU terrible network performance trought NAT

[laurent.cligny at gmail.com]

Le 12/05/2011 17:48, Janne Snabb a écrit :
> On Thu, 12 May 2011, Laurent Cligny wrote:
>
>> All FreeBSD VM are 8.2 amd64 with XENHVM kernel anf the Linux VM is a
>> Paravirtualized Debian amd64.
> My suggestion would be to try out the same setup with GENERIC kernel
> and the rtl driver (or even better e1000 if your Xen allows it)
> which is easy to do to make a simple comparison.
I tried it following your idea. I compiled GENERIC kernel on both NAT Vm
and Vm behind the NAT, the network perf increased a lot as it is now
about 15Mb/s trough NAT and between the VM on the private network. But
doing this also eat a lot of CPU on "Sys" context (almost 50% on SMP).
So I think it is not a suitable setup for me.
> In one of my recent benchmarks the FreeBSD Xen PV network driver
> performed very well in one direction, but very badly in the other.
> Using rtl or e1000 gave much better TCP throughput if you care
> equally about both directions. This benchmark was done only for
> internal TCP traffic between a Linux dom0 and FreeBSD dumU, the
> traffic never entered a real NIC.
In fact I have great troughput between VM on private NIC with XENHVM
kernel (50 to 70 Mb/s) and also from NAT VM to Internet on public NIC.
The problem appears when I generate traffic from VMs on private network
to and from the Internet trough the NAT VM.
> This might or might not help in your situation...
It has conforted me into the idea that XENHVM kernel doesn't work well
with FreeBSD NAT solutions or with the underlying Xen Cloud Platform Dom0.
> --
> Janne Snabb / EPIPE Communications
> snabb at epipe.com - http://epipe.com/
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