On Wed, Jul 29, 2009 at 03:26:37PM -0700, Robert Bays wrote:
>
> On 7/29/09 11:57 AM, Alexis Rosen wrote:
> > 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.
>
> At my company, we have done extensive testing of the forwarding
> performance of Linux vms on Xen. We use Quagga as our routing suite,
> but as previously mentioned it has nothing to do with forwarding
> performance. I removed the Quagga list from this thread to stop the
> cross post.
>
> For testing we follow rfc2544. To give you some representative numbers,
> we see anywhere between 100-150mbps zero loss throughput for
> bi-directional 64byte packet streams on a 3.0ghz Intel quad core
> processor. This follows the typical bandwidth curve up to roughly
> 1.6gig for large packet sizes. We are currently running a Linux 2.6.30
> pv_ops enabled kernel in the domU. We have noticed that if we share a
> physical processor core with more than one vm we will take a roughly 2%
> hit to overall performance. Interestingly, a third or fourth vm on the
> same core still only incurs the same 2% penalty. Throughput is highly
> dependent on the system; i.e. processor model, motherboard chipsets, bus
> type and location of the card on the bus, etc... Throughput also has a
> fairly high jitter factor. The system can be tuned to mitigate the
> jitter, but at a loss of overall throughput and an average increase in
> latency.
>
Interesting. Did you profile what limits the performance, or uses the cpu?
Bridging in dom0? Xen?
Are you familiar with the netchannel2 development stuff?
> If the system is configured for PCI pass through, expect a much higher
> throughput. It's more on the order of 650mbps zero-loss for
> bi-directional streams of small packet sizes. HVM domUs aren't even
> worth using for networking.
>
Yeah, PV guests are much easier, faster and stable for this purpose.
(and yeah I know you can use PV-on-HVM drivers on HVM domain).
-- Pasi
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