[et-mgmt-tools] Re: [Xen-devel] Xen, Windows 2003 and APIC

[Gary Pennington]

On Fri, Dec 05, 2008 at 04:42:57PM +0000, George Dunlap wrote:
> IIRC, only w2k3sp2+, vista, and w2k8 have lazy TPR.  Not positive
> about w2k3sp1, but I think it doesn't.  WinXP does not have lazy TPR
> in any service pack, AFAIK.
> 
> What service pack of w2k3 did you do those tests with?
> 

I'm not sure, because the ISO was provided by a colleague. I think it's
the original release of w2k3, with no service packs.

However, what I was mostly curious about was why specifying apic when the
guest was created made so much different to performance.

Gary

> Hopefully, sometime in the next few weeks, I'll be able to release my
> 'xenalyze' tool, which will help a lot with analyzing what's really
> going on with these kinds of workloads.
> 
>  -George
> 
> On Fri, Dec 5, 2008 at 2:45 PM, Keir Fraser <keir.fraser at eu.citrix.com> wrote:
> > On 05/12/2008 14:03, "Gary Pennington" <Gary.Pennington at sun.com> wrote:
> >
> >> My next question is: What is really happening when APIC is specified for
> >> a windows guest and why does performance vary so much according to whether
> >> it's specified or not?
> >
> > Older Windows kernels update the APIC TPR a lot, and unless you have a very
> > modern Intel processor every one of those TPR updates causes a vmexit.
> >
> > Modern Windows (including possibly latest w2k3 service pack, but I'm not
> > totally certain) includes lazy TPR, which gets rid of the vast majority of
> > TPR updates, and hence will go much faster.
> >
> >  -- Keir
> >
> >
> >
> > _______________________________________________
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> > Xen-devel at lists.xensource.com
> > http://lists.xensource.com/xen-devel
> >
> 
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-- 
Gary Pennington
Solaris Core OS
Sun Microsystems
Gary.Pennington at sun.com