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Re: [Xen-users] OS kernels ports, VT, Pacifica & performance

To: Sylvain Coutant <sco@xxxxxxxxxx>
Subject: Re: [Xen-users] OS kernels ports, VT, Pacifica & performance
From: Anthony Liguori <aliguori@xxxxxxxxxx>
Date: Thu, 17 Nov 2005 11:09:30 -0600
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Sylvain Coutant wrote:

Hi all,

First, I'm not sure this post should have been sent to xen-devel or here. 
Please, any list owner : forward to xen-devel if you read this and feel it 
should have gone there.

I wonder what will be the advantage, in terms of performance, of having 
optimized kernels for XenU when VT/Pacifica will be there.
It's pretty much a rule that anytime you optimize something to run in a VMM, it's going to improve performance. The real question is whether that performance is noticable.

My initial feeling is that there are going to be some noticable performance optimizations one can make for running under VT/Pacifica without actually requiring Xen-only modifications (changing page table writes for instance to be more like writable page tables).

AFAIK, using "standard" kernels means emulating peripherals (network card and so on) on dom0. Xen 
"optimized" or "ported" kernels should have a performance advantage. But has this perf 
increase already been evaluated ?
There's quite a bit of ongoing research about whether it's possible to make native-performance emulated drivers. The theory is that if you choose the right hardware to emulate, you could potentially have a emulation model that looks a lot like what a paravirtual driver would look like anyway.


Anthony Liguori

Question behind this : does it worth the work to port some other OSes to Xen 
architecture ?




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