This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
Home Products Support Community News


Re: [Xen-devel][PATCH][RFC] SupportingEnlightenedWindows2008Server

To: "Tim Deegan" <Tim.Deegan@xxxxxxxxxx>, "Keir Fraser" <keir.fraser@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel][PATCH][RFC] SupportingEnlightenedWindows2008Server
From: "Ky Srinivasan" <ksrinivasan@xxxxxxxxxx>
Date: Sun, 13 Apr 2008 13:05:38 -0600
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
Delivery-date: Sun, 13 Apr 2008 12:06:06 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxx
List-help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id: Xen developer discussion <xen-devel.lists.xensource.com>
List-post: <mailto:xen-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx

>>> 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.


K. Y
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-devel

Xen-devel mailing list

<Prev in Thread] Current Thread [Next in Thread>