Re: Xen I/O performance

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Mon, May 19, 2008 at 10:25:40PM +0100, Matthias Scheler wrote:
> 
>       Hello,
> 
> in the past NetBSD Xen was often blamed to cause a massive loss of
> I/O performance on the dom0 compared to a machine not using Xen.
> In my attempt to evaluate NetBSD Xen for use on my new server at
> home I've run two benchmarks:
> 
> 1.) Extracting all the NetBSD 4.0 release source sets (located on a
>     tmpfs) to at the same empty local filesystem using "tar"
> 
> 2.) Copying 32GB from "/dev/zero" to a file on the same non-empty
>     filesystem using "dd".
> 
> The machine used for the test is a Xeon 3040 (Core 2 Duo architecture,
> 1.87GHz, two cores) with 5GB memory and a single 160GB SATA harddisks.
> I've used the 4.99.63 NetBSD-amd64 GENERIC and XEN3_DOM0 kernels. The
> amd64 kernel could use two CPU cores and 5GB memory, the Xen kernel
> only one CPU core and 3.5GB memory.
> 
> Here are the results:
> 
> Kernel                "tar" (time in minutes)         "dd" (throughput in 
> bytes/sec)
> GENERIC               4:19.31                         46391830
> XEN3_DOM0     3:59.20                         47161618
> 
> I'm impressed. The Xen kernel did much better than I expected.
> Congratulations to Manuel for with excellent work.

I admit I don't know why it's faster under Xen than with a native kernel :)
Maybe it's due to the overload of SMP with this workload ?

-- 
Manuel Bouyer, LIP6, Universite Paris VI.           
Manuel.Bouyer%lip6.fr@localhost
     NetBSD: 26 ans d'experience feront toujours la difference
--