From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Ky Srinivasan" Subject: Re: [PATCH][RFC] SupportingEnlightenedWindows2008Server Date: Sun, 13 Apr 2008 12:43:49 -0600 Message-ID: <48DF40A6.E57C.0030.0@novell.com> References: <48ABEA14.E57C.0030.0@novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: Content-Disposition: inline List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Tim Deegan , Keir Fraser Cc: xen-devel@lists.xensource.com List-Id: xen-devel@lists.xenproject.org >>> On Tue, Apr 8, 2008 at 1:15 PM, in message , Keir Fraser wrote:=20 > On 8/4/08 18:03, "Ky Srinivasan" wrote: >=20 >> From a performance point of view, I think the MSR access to APIC = registers=20 > 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=20 > other >> synthetic MSRs support features that the current windows 2008 server=20 > currently >> is not using (timeouts for example). >=20 > 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. >=20 > 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 >=20 > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel