[Xen-users] Re: [quagga-users 10973] Quagga on Xen - Latency / Bandwidth?

[Alexis Rosen <alexis@xxxxxxxxx>]

On Jul 29, 2009, at 4:04 AM, Robert Dunkley wrote:
> I was wondering if anyone is running Quagga on Xen? What is
> throughput/latency like?
>
> Was looking for about a gig of mixed packet size BGP throughput.
Presumably you mean internet traffic.

On bare metal (no Xen), that will work fine for mixed Internet  
traffic, but you need to think about corner cases. What do you expect  
to have happen when you get DDoSed with minimum-size packets? I don't  
think even the multiqueue GbE cards will let you handle that, but I  
have not tested that, and I'd love to be proven wrong.
I'm also under the impression that Linux 2.6.30 kernels have some  
significant patches to make (better?) use of multiqueue cards but I  
don't remember the details. Maybe 2.6.30 can distribute ksoftirqd load  
over multiple cores? If so that's a big win, as that was the killer  
with large PPS when we tested on somewhat less powerful hardware with  
an older kernel, and you can probably handle a full gbps of min-sized  
packets if you give it a number of cores (and you have enough queues).
Another question to think about (sorry, no answers here, just  
questions): If you do run under Xen, is there interrupt load in both  
the dom0 and the domU? In that case you'll get pounded. Maybe  
dedicating an entire Ethernet port to the domU is a way to work around  
that. I know Xen3 has provisions for that sort of thing but I haven't  
used it.
/a

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