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xen-devel
Re: [Xen-devel][PATCH][RFC] SupportingEnlightenedWindows2008Server
>>> On Tue, Apr 8, 2008 at 1:15 PM, in message
<C42166D1.16177%keir.fraser@xxxxxxxxxxxxx>, Keir Fraser
<keir.fraser@xxxxxxxxxxxxx> wrote:
> On 8/4/08 18:03, "Ky Srinivasan" <ksrinivasan@xxxxxxxxxx> wrote:
>
>> From a performance point of view, I think the MSR access to APIC registers
> are
>> the most important. As far as hypercalls go, the only one currently
>> implemented is the hypercall to change the page table base. Some of the
> other
>> synthetic MSRs support features that the current windows 2008 server
> currently
>> is not using (timeouts for example).
>
> That's a bit surprising since w2k8 probably accesses the TPR via %cr8, for
> which we implement vmexit mitigation. The only other APIC register that is
> often accessed is EOI. We can't avoid the vmexit for that, and the extra
> cost of not having an explicit MSR for it is a run through the mmio
> emulator. I'd be surprised if avoiding the run through the emulator per
> interrupt was that much of a win.
>
> Anyhow, you should be able to switch off HyperV features selectively, as
> advertised to the domU HVM guest, and see which ones make a difference to
> performance.
The benchmark was run a while ago on some very early sles10 sp2 bits (late last
fall/winter). It is by selectively enabling HyperV functionality that I
concluded that APIC MSR access was the most important enlightenment based on
NetBench results. We are in the process of running a range of benchmarks. I
will keep you posted.
Regards,
K. Y
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-devel
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