Re: [Xen-users] Xen Performance

Pasi Kärkkäinen
Tue, 26 May 2009 14:50:33 -0000

On Sun, May 24, 2009 at 12:12:23PM +0200, Amir Maqbool Ahmed
wrote:
> Hi
>
> I am a student at the University College of Oslo and have in one experiment
> tried to test the performance of Xenolinux compared to Native linux on
Debian lenny
> 2.6.26-2 kernel.
>
> bonnie++ the disk IO bechmark program was used among other tests like cpu
intensive scripts.
> The goal is to prove the statement (Once again) that Xen adds only an
overhead of maximum 8%.
>
> The Results of bonnie++ have been surprizing and I want to explain them.
> It shows that for some types of Disk IO, like sequential delete and random
create
> Xen performs faster than native linux. A full comparison chart is attached
as a pdf.
> The test are run first from native linux than both from Dom0 and a DomU
with the same results.
>
> Can you please help me understand these results, How can Xenolinux perform
faster
> although only for some types of operations, then native linux?
>
> Plese forgive me If Im missing something completely obvious.
> If you need any further info. please just send me an email and it will be
provided.
>
> Hope to hear from you soon
>

Hi,

Usually this is caused by using file backed disks for domU, so dom0
kernel file cache is giving this boost..

Change to LVM volumes or tap:aio instead of file, because they don''t
have
dom0 (file) caching..

-- Pasi