From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757792Ab2DJLH6 (ORCPT ); Tue, 10 Apr 2012 07:07:58 -0400 Received: from mx1.redhat.com ([209.132.183.28]:65243 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752915Ab2DJLH4 (ORCPT ); Tue, 10 Apr 2012 07:07:56 -0400 Message-ID: <4F840DD2.3090101@redhat.com> Date: Tue, 10 Apr 2012 13:39:14 +0300 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:11.0) Gecko/20120316 Thunderbird/11.0 MIME-Version: 1.0 To: Marcelo Tosatti CC: Xiao Guangrong , Xiao Guangrong , LKML , KVM Subject: Re: [PATCH 00/13] KVM: MMU: fast page fault References: <4F742951.7080003@linux.vnet.ibm.com> <4F82E04E.6000900@redhat.com> <20120409175829.GB21894@amt.cnet> <4F8329D3.7000605@gmail.com> <20120409194614.GB23053@amt.cnet> In-Reply-To: <20120409194614.GB23053@amt.cnet> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/09/2012 10:46 PM, Marcelo Tosatti wrote: > Perhaps the mmu_lock hold times by get_dirty are a large component here? > If that can be alleviated, not only RO->RW faults benefit. > > Currently the longest holder in normal use is probably reading the dirty log and write protecting the shadow page tables. We could fix that by switching to O(1) write protection (write-protecting PML4Es instead of PTEs). It would be interesting to combine O(1) write protection with lockless write-enabling. -- error compiling committee.c: too many arguments to function