From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753649AbXCPUrV (ORCPT ); Fri, 16 Mar 2007 16:47:21 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753650AbXCPUrV (ORCPT ); Fri, 16 Mar 2007 16:47:21 -0400 Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:40926 "EHLO sunset.davemloft.net" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1753639AbXCPUrU (ORCPT ); Fri, 16 Mar 2007 16:47:20 -0400 Date: Fri, 16 Mar 2007 13:47:18 -0700 (PDT) Message-Id: <20070316.134718.95058720.davem@davemloft.net> To: clameter@sgi.com Cc: andi@firstfloor.org, rostedt@goodmis.org, torvalds@linux-foundation.org, mbligh@mbligh.org, mingo@elte.hu, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, chrisw@sous-sol.org, rusty@rustcorp.com.au, glommer@gmail.com Subject: Re: [PATCH 00/18] Make common x86 arch area for i386 and x86_64 - Take 2 From: David Miller In-Reply-To: References: <20070316114415.GA26403@one.firstfloor.org> X-Mailer: Mew version 5.1.52 on Emacs 21.4 / Mule 5.0 (SAKAKI) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org From: Christoph Lameter Date: Fri, 16 Mar 2007 13:15:38 -0700 (PDT) > On Fri, 16 Mar 2007, Andi Kleen wrote: > > > > x86_64 is going to acquire more functionality that will not be available > > > for i386. We plan f.e. to add virtual memmap support for x86_64. Virtual > > > > What advantage would that have over the current setup? > > We already should handle holes between nodes reasonably efficiently > > and with nonlinear memory even holes inside nodes shouldn't be a problem. > > It is primarily a performance improvement since the sparsemem table > lookups would no longer be necessary and it also streamlines other > frequent cacheline uses. These page -> page_struct and vice versa > operations are key to the performance of various subsystem among them > the slab allocator. If you set the bit range small enough and don't use sparsemem-extreme, the cost is extremely low considering the flexibility you obtain. There are always going to be holes on large systems, there isn't really a way to avoid this given how addressing is done on those machines.