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

[Alexis Rosen <quagga-users@xxxxxxxxxxxxxxxxxxxxxx>]

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.
/a

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