Re: [Xen-users] Xen Performance

[Peter Booth <peter_booth@xxxxxxx>]

The original question doesn't say "as measured on Dom0", and appears to reference the well known

study performed at Cambridge University and replicated at Clarkson University. That study used a handful

of benchmarks and compared throughput across a number of virtualization platforms. It found that, for those

tests, Xen throughput was, at most, only 8% worse than native Linux. 

The issue for our community, however, is that it is human nature to use the "at most 8% worse" 

as a data-point for Xen performance.  But throughput is not the whole picture. Many Xen installations 

are hosting user-facing web applications where response time is much more important than throughput.

Xen often increases the variability of response times.

One real world example:

native Linux:   page response times of (  400ms/150ms) [mean/standard deviation]

Xen VM: page response times of (  700ms/3.5s) [mean/standard deviation]

In this scenario, we have mean response times that are almost 100% worse, and the 90th percentile is 1000% worse.

Peter Booth

 

On May 28, 2009, at 1:08 PM, Javier Guerra wrote:

On Thu, May 28, 2009 at 11:57 AM, Peter Booth <peter_booth@xxxxxxx> wrote:

The 8% is a dangerous over-simplification, and represents simply the results

of a particular well-designed study.

 Clearly there are situations where the overhead of using Xen is much higher

than this.

but not as measured on Dom0, as i think the original question was

--
Javier

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