From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751599Ab3KSBHm (ORCPT ); Mon, 18 Nov 2013 20:07:42 -0500 Received: from mx1.redhat.com ([209.132.183.28]:6047 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751064Ab3KSBHl (ORCPT ); Mon, 18 Nov 2013 20:07:41 -0500 Date: Mon, 18 Nov 2013 22:48:13 -0200 From: Marcelo Tosatti To: Xiao Guangrong Cc: gleb@redhat.com, avi.kivity@gmail.com, pbonzini@redhat.com, linux-kernel@vger.kernel.org, kvm@vger.kernel.org Subject: Re: [PATCH v3 06/15] KVM: MMU: redesign the algorithm of pte_list Message-ID: <20131119004812.GA22049@amt.cnet> References: <1382534973-13197-1-git-send-email-xiaoguangrong@linux.vnet.ibm.com> <1382534973-13197-7-git-send-email-xiaoguangrong@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1382534973-13197-7-git-send-email-xiaoguangrong@linux.vnet.ibm.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 23, 2013 at 09:29:24PM +0800, Xiao Guangrong wrote: > Change the algorithm to: > 1) always add new desc to the first desc (pointed by parent_ptes/rmap) > that is good to implement rcu-nulls-list-like lockless rmap > walking > > 2) always move the entry in the first desc to the the position we want > to remove when delete a spte in the parent_ptes/rmap （backward-move). > It is good for us to implement lockless rmap walk since in the current > code, when a spte is deleted from the "desc", another spte in the last > "desc" will be moved to this position to replace the deleted one. If the > deleted one has been accessed and we do not access the replaced one, the > replaced one is missed when we do lockless walk. > To fix this case, we do not backward move the spte, instead, we forward > move the entry: when a spte is deleted, we move the entry in the first > desc to that position > > Both of these also can reduce cache miss > > Signed-off-by: Xiao Guangrong Reviewed-by: Marcelo Tosatti