[CentOS-virt] performance differences between kvm/xen

Tue Oct 19 07:41:24 UTC 2010
Pasi Kärkkäinen <pasik at iki.fi>

On Sat, Oct 16, 2010 at 09:58:15PM +0200, Dennis Jacobfeuerborn wrote:
> On 10/16/2010 08:11 PM, Pasi Kärkkäinen wrote:
> > On Thu, Oct 14, 2010 at 02:16:42PM +0100, Bart Swedrowski wrote:
> >> Hi Karanbir,
> >>
> >> On 14 October 2010 19:59, Karanbir Singh<mail-lists at karan.org>  wrote:
> >>>
> >>> On 10/14/2010 07:48 AM, Tom Bishop wrote:
> >>>> I think xen is still on top in terms of performance and features....now
> >>>
> >>> that is indeed what it 'feels' like, but I'm quite keen on putting some
> >>> numbers on that.
> >>
> >> I have done some testing some time ago on one of the EQ machines that
> >> I got from hetzner.de.  Full spec of the machine was as following:
> >>
> >>    * Intel® Core??? i7-920
> >>    * 8 GB DDR3 RAM
> >>    * 2 x 750 GB SATA-II HDD
> >>
> >> It's nothing big but even though results are quite interesting.  All
> >> tests were performed on CentOS 5.5 x86_64 with PostgreSQL 8.4 (from
> >> CentOS repos).
> >>
> >
> > Note that 64bit Xen guests should be HVM, not PV, for best performance.
> > Xen HVM guests obviously still need to have PV-on-HVM drivers installed.
> >
> > 32bit Xen guests can be PV.
> 
> Hm, why would HVM be faster than PV for 64 bit guests?
> 

It's because of the x86_64 architecture, afaik.

There was some good technical explananation about it,
but I can't remember the url now.

-- Pasi