From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH 00/13] KVM: MMU: fast page fault Date: Tue, 10 Apr 2012 13:39:14 +0300 Message-ID: <4F840DD2.3090101@redhat.com> References: <4F742951.7080003@linux.vnet.ibm.com> <4F82E04E.6000900@redhat.com> <20120409175829.GB21894@amt.cnet> <4F8329D3.7000605@gmail.com> <20120409194614.GB23053@amt.cnet> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Xiao Guangrong , Xiao Guangrong , LKML , KVM To: Marcelo Tosatti Return-path: 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 In-Reply-To: <20120409194614.GB23053@amt.cnet> Sender: kvm-owner@vger.kernel.org List-ID: 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