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[Xen-users] Re: [quagga-users 10975] Re: Quagga on Xen - Latency / Bandw

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Subject: [Xen-users] Re: [quagga-users 10975] Re: Quagga on Xen - Latency / Bandwidth?
From: Robert Bays <robert@xxxxxxxxxx>
Date: Wed, 29 Jul 2009 15:26:37 -0700
Cc: sthaug@xxxxxxxxxx
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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

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.

Hope that helps.


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