Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753574Ab2ECMNy (ORCPT ); Thu, 3 May 2012 08:13:54 -0400 Received: from mx1.redhat.com ([209.132.183.28]:14791 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752432Ab2ECMNx (ORCPT ); Thu, 3 May 2012 08:13:53 -0400 Message-ID: <4FA2767B.5010707@redhat.com> Date: Thu, 03 May 2012 15:13:47 +0300 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:11.0) Gecko/20120329 Thunderbird/11.0.1 MIME-Version: 1.0 To: Xiao Guangrong CC: Marcelo Tosatti , Takuya Yoshikawa , LKML , KVM Subject: Re: [PATCH v4 06/10] KVM: MMU: fast path of handling guest page fault References: <4F9776D2.7020506@linux.vnet.ibm.com> <4F9777A4.208@linux.vnet.ibm.com> <20120426234535.GA5057@amt.cnet> <4F9A3445.2060305@linux.vnet.ibm.com> <20120427145213.GB28796@amt.cnet> <20120429175004.b54d8c095a60d98c8cdbc942@gmail.com> <4FA0C8A7.9000001@linux.vnet.ibm.com> <20120502211031.GB12604@amt.cnet> <4FA27578.1010509@linux.vnet.ibm.com> In-Reply-To: <4FA27578.1010509@linux.vnet.ibm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1253 Lines: 29 On 05/03/2012 03:09 PM, Xiao Guangrong wrote: > Actually, the improvement of lockless is that it can let vcpu to be parallel > as possible. > > From the test result, lockless gains little improvement for unix-migration, > in this case, the vcpus are almost idle (at least not busy). > > The large improvement is from dbench-migration, in this case, all vcpus are > busy accessing memory which is write-protected by dirty-log. If you enable > page-fault/fast-page-fault tracepoints, you can see huge number of page fault > from different vcpu during the migration. > We can kill the page faults completely by using A/D bits in shadow page tables. The latest version of the Intel SDM defines A/D bits for EPT, and NPT has had them from day one. Of course this comes at a cost, instead of traversing a bitmap we have to read all sptes, which are 64x as large. But it's probably worthwhile for large guests and perhaps also for smaller ones. -- error compiling committee.c: too many arguments to function -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/