From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH] lighweight VM Exit Date: Tue, 15 May 2007 10:39:15 +0300 Message-ID: <464963A3.7090505@qumranet.com> References: <10EA09EFD8728347A513008B6B0DA77A016FC1F2@pdsmsx411.ccr.corp.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel To: "Dong, Eddie" Return-path: In-Reply-To: <10EA09EFD8728347A513008B6B0DA77A016FC1F2-wq7ZOvIWXbNpB2pF5aRoyrfspsVTdybXVpNB7YpNyf8@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: kvm.vger.kernel.org Dong, Eddie wrote: > Avi Kivity wrote: > >> Why not use hardware autoloading? Is it slower than software? >> > > I believe HW is faster than SW, but the problem is that this kind of > save/restore is > only needed for heavy weight VM Exit in KVM. While HW doesn't provide an > easy > way to bypass these MSR save/restore for light weight VM Exit, we have > to do > that in SW. > k. > >> Otherwise looks good. Did you measure performance improvement? I >> usually use user/test/vmexit.c from kvm-userspace.git. >> >> > > Yes, I tested RHEL5 64 bits guest, in my old Pentium 4 platform, I get > 4.9% > performance increasement using Kernel Builder as workload. In my 4 core > Clovertown platform (Core 2 Duo), I get 5.4% performance increasement. > 32 bits guest test didn't show regression either. > Further improvement can be made base on this patch such as MSR_EFER > virtualization. > > thx,eddie > > A slight revise per Christoph's comments. > You missed my comments regarding coding style. -- Do not meddle in the internals of kernels, for they are subtle and quick to panic. ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/