From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2992655AbXDTIm1 (ORCPT ); Fri, 20 Apr 2007 04:42:27 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S2992648AbXDTIm0 (ORCPT ); Fri, 20 Apr 2007 04:42:26 -0400 Received: from netops-testserver-4-out.sgi.com ([192.48.171.29]:38240 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2992642AbXDTImX (ORCPT ); Fri, 20 Apr 2007 04:42:23 -0400 Date: Fri, 20 Apr 2007 18:42:06 +1000 From: David Chinner To: William Lee Irwin III Cc: Christoph Lameter , linux-kernel@vger.kernel.org, Peter Zijlstra , Nick Piggin , Paul Jackson , Dave Chinner , Andi Kleen Subject: Re: [RFC 0/8] Variable Order Page Cache Message-ID: <20070420084206.GO32602149@melbourne.sgi.com> References: <20070419163504.11948.58487.sendpatchset@schroedinger.engr.sgi.com> <20070420044718.GV2986@holomorphy.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070420044718.GV2986@holomorphy.com> User-Agent: Mutt/1.4.2.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 19, 2007 at 09:47:18PM -0700, William Lee Irwin III wrote: > On Thu, Apr 19, 2007 at 09:35:04AM -0700, Christoph Lameter wrote: > > This patchset modifies the core VM so that higher order page cache pages > > become possible. The higher order page cache pages are compound pages > > and can be handled in the same way as regular pages. > > The order of the pages is determined by the order set up in the mapping > > (struct address_space). By default the order is set to zero. > > This means that higher order pages are optional. There is no attempt here > > to generally change the page order of the page cache. 4K pages are effective > > for small files. > > Oh dear. Per-file pagesizes are foul. Better to fix up the pagecache's > radix tree than to restrict it like this. How is this restrictive? This opens up much goodness to filesystems. I *want* to be able to use different radix tree index orders for different inodes in a single filesystem. Not just for data, either; XFS has metadata constructs larger than a page that mean we have to carry our own buffer cache around. Being able to use the page cache directly for these metadata constructs would enable us to remove a good chunk of code from XFS.... Cheers, Dave. -- Dave Chinner Principal Engineer SGI Australian Software Group