From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH v4 06/10] KVM: MMU: fast path of handling guest page fault Date: Sun, 06 May 2012 12:36:12 +0300 Message-ID: <4FA6460C.8020702@redhat.com> 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> <4F9B89D9.9060307@linux.vnet.ibm.com> <20120501013459.GB10142@amt.cnet> <4FA0C607.5010002@linux.vnet.ibm.com> <20120502210701.GA12604@amt.cnet> <4FA26B6E.408@linux.vnet.ibm.com> <20120505140836.GC11842@amt.cnet> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Xiao Guangrong , LKML , KVM To: Marcelo Tosatti Return-path: Received: from mx1.redhat.com ([209.132.183.28]:41028 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752221Ab2EFJgi (ORCPT ); Sun, 6 May 2012 05:36:38 -0400 In-Reply-To: <20120505140836.GC11842@amt.cnet> Sender: kvm-owner@vger.kernel.org List-ID: On 05/05/2012 05:08 PM, Marcelo Tosatti wrote: > It would be better if all these complications introduced by lockless > updates can be avoided, say using A/D bits as Avi suggested. Note that using A/D bits introduces new tradeoffs (when just a few bits are dirtied per iteration, we reduce guest overhead, but increase host overhead, since it has to scan a large number of sptes), and also a large fraction of deployed systems don't have A/D bits support. But it should affect our thinking - since in the long term all hosts will have it. -- error compiling committee.c: too many arguments to function