From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752352AbXDBRek (ORCPT ); Mon, 2 Apr 2007 13:34:40 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752654AbXDBRek (ORCPT ); Mon, 2 Apr 2007 13:34:40 -0400 Received: from netops-testserver-4-out.sgi.com ([192.48.171.29]:59440 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752366AbXDBRej (ORCPT ); Mon, 2 Apr 2007 13:34:39 -0400 Date: Mon, 2 Apr 2007 10:34:38 -0700 (PDT) From: Christoph Lameter X-X-Sender: clameter@schroedinger.engr.sgi.com To: Andi Kleen cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, Martin Bligh , linux-mm@kvack.org, KAMEZAWA Hiroyuki Subject: Re: [PATCH 1/4] x86_64: Switch to SPARSE_VIRTUAL In-Reply-To: <200704021914.07541.ak@suse.de> Message-ID: References: <20070401071024.23757.4113.sendpatchset@schroedinger.engr.sgi.com> <200704021744.39880.ak@suse.de> <200704021914.07541.ak@suse.de> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2 Apr 2007, Andi Kleen wrote: > > No no no. For the gazillions time: All of 1-1 mapped kernel memory on > > x86_64 needs a 2 MB page table entry. The virtual memmap uses the same. > > There are *no* additional TLBs used. > > But why do you reserve an own virtual area then if you claim to not use any > additional mappings? The 1-1 area using mappings for 2MB pages right? So it uses a virtual 1-1 area. It already has a virtual mapping. What we do for virtual memmap here is also use 2MB pages but order the pages a bit different so that they provide a linear memory map. So the number of TLBs in use stays the same. There are a few additional higher level page table pages that are needed to provide the alternate view that generates the linear mapping but that is just a couple of pages.