From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [Qemu-devel] Ideas wiki for GSoC 2010 Date: Tue, 16 Mar 2010 08:12:00 +0200 Message-ID: <4B9F2130.6030903@redhat.com> References: <20100310183023.6632aece@redhat.com> <4B9E2745.7060903@redhat.com> <20100315125313.GK9457@il.ibm.com> <20100315130310.GE13108@8bytes.org> <4B9E320E.7040605@redhat.com> <4B9E34E1.3090709@codemonkey.ws> <4B9E4D11.70402@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org To: Jason Return-path: Received: from mx1.redhat.com ([209.132.183.28]:61324 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757311Ab0CPGMF (ORCPT ); Tue, 16 Mar 2010 02:12:05 -0400 In-Reply-To: Sender: kvm-owner@vger.kernel.org List-ID: On 03/16/2010 02:20 AM, Jason wrote: > > In comparing KVM 2.6.31.6b to XenServer 5.5.0, it seems KVM has fewer overall > VMREADs and VMWRITEs, but there are a lot of VMWRITEs to Host FS_SEL, Host > GS_SEL, Host FS_BASE, and Host GS_BASE that don't appear in Xen. Ugh, these should definitely be eliminated, they keep writing the same value most of the time. > Also, KVM has a > lot of MSR accesses to 0xc0000081-0xc0000084 that Xen doesn't have. > These are unavoidable. Those msrs are used for system calls and we need them to keep ordinary userspace going. 2.6.33 should reduce their frequency though. Usually it doesn't make sense to pass them through, but if we detect the guest is writing them often, we can do so and eliminate the exits. -- Do not meddle in the internals of kernels, for they are subtle and quick to panic.