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[Xen-users] Re: [quagga-users 10974] Re: Quagga on Xen - Latency / Bandw

On Jul 29, 2009, at 5:17 AM, sthaug@xxxxxxxxxx wrote:
I was wondering if anyone is running Quagga on Xen? What is
throughput/latency like?

This is a function of kernel forwarding performance. Quagga doesn't
do forwarding.

But the question is still of significant importance to a lot of Quagga users. Thus, I suggest that it is an appropriate topic for the list.

Here's my earlier reply, which I (again, damnit) failed to send to the list from an authorized address:

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.


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