Xen users - May 2006 - RE: poor harddisk performance HVM domain (Windows 2003guest)

> -----Original Message-----
> From: Matthijs ter Woord [mailto:matthijsterwoord@gmail.com] 
> Sent: 08 May 2006 12:08
> To: Petersson, Mats; Joost van den Broek; 
> xen-users@lists.xensource.com
> Subject: Re: [Xen-users] poor harddisk performance HVM domain 
> (Windows 2003guest)
> 
> Is VMWare + HVM then slow too?
I don''t know - but the slowness isn''t so much HVM as the way
that
hardware is emulated in Xen and most importantly that there''s no
current
support for para-virtual drivers, or any drivers, in Xen. 

The same scenario without HVM wouldn''t be faster - just much harder to
do the virtualization. It''s the "save everything, go off do
something
else and return" that takes the time. In a non-HVM solution, you get
"save everything, figure out what is going on [what caused the exception
or whatever it is], go off do something else and return". So it''s
actually faster to do it this way, it''s just that either way is a lot
slower than runing on real hardware... A single IO access to a 33MHz PCI
device takes around 300 clock cycles on a modern (2GHz) machine, so
it''s
not going to be that immediate even on real hardware... 

--
Mats
> 
> 
> 
> ----- Original Message -----
> From: "Petersson, Mats" <Mats.Petersson@amd.com>
> To: "Matthijs ter Woord" <matthijsterwoord@gmail.com>;
"Joost
> van den Broek"
> <joost@seat-ibiza.nl>; <xen-users@lists.xensource.com>
> Sent: Monday, May 08, 2006 12:03 PM
> Subject: RE: [Xen-users] poor harddisk performance HVM domain (Windows
> 2003guest)
> 
> 
> 
> 
> > -----Original Message-----
> > From: xen-users-bounces@lists.xensource.com
> > [mailto:xen-users-bounces@lists.xensource.com] On Behalf Of 
> Matthijs 
> > ter Woord
> > Sent: 08 May 2006 10:30
> > To: Joost van den Broek; xen-users@lists.xensource.com
> > Subject: Re: [Xen-users] poor harddisk performance HVM 
> domain (Windows 
> > 2003guest)
> >
> > <wishful thinking>
> >
> > Would a AoE driver for windows do the job too in combination with a 
> > AoE server xen machine?
> >
> > </wishful thinking>
> >
> Unfortunately the answer is no, because the network 
> performance from HVM is equally hampered by the intercepts 
> and context switches as the IDE performance.
> 
> --
> Mats
> 
> 
> 

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