Re: Running XEN under a Linux AMD64 DOM0

[Christoph Egger <Christoph_Egger%gmx.de@localhost>]

On Monday 31 March 2008 00:45:55 Luke S Crawford wrote:
> Carl Brewer <carl%bl.echidna.id.au@localhost> writes:
> > As a general suggestion, would you advise amd64-current or
> > i386-current for a xen dom0 server with 6GB of RAM with HVM-aware
> > cpu's to get the best of a modern Intel C2D server?  Core2duo 8200 is
> > hvm aware and I believe i386-cuurent is PAE capable also?  There'd be
> > little/no performance impact from using HVM?
>
> Uh, just saying, HVM mode takes a pretty significant performance hit when
> it comes to I/O (file or network)  -  there's not much overhead if all you
> do is cpu/memory access, as the intel vt takes care of that; but once you
> start hitting disk or network, I believe Xen emulates real hardware using
> code pulled from qemu.

That's right. On NetBSD the PV drivers are bound to the PV kernel.
The PV drivers are not available in the GENERIC kernels, therefore
no PV drivers with NetBSD as HVM guest.

> On windows the hit can be reduced by installing special xen-aware
> 'paravirtualized drivers'  that help to reduce the I/O overhead while
> still running in HVM mode.  I don't know of anything like that for
> Linux or NetBSD.

On Linux you can do all combinations: PV Linux-kernel with PV drivers,
native Linux-kernel with PV drivers, native Linux-kernel w/o PV drivers.

PV drivers for windows are under development.


Christoph