From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1767211AbXDTT1v (ORCPT ); Fri, 20 Apr 2007 15:27:51 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1767212AbXDTT1v (ORCPT ); Fri, 20 Apr 2007 15:27:51 -0400 Received: from e1.ny.us.ibm.com ([32.97.182.141]:52990 "EHLO e1.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1767211AbXDTT1u (ORCPT ); Fri, 20 Apr 2007 15:27:50 -0400 Subject: Re: [RFC 4/8] Enhance fallback functions in libs to support higher order pages From: Dave Kleikamp To: Christoph Lameter Cc: Mel Gorman , linux-kernel@vger.kernel.org, Peter Zijlstra , Nick Piggin , Andi Kleen , Paul Jackson , Dave Chinner In-Reply-To: References: <20070419163504.11948.58487.sendpatchset@schroedinger.engr.sgi.com> <20070419163525.11948.3482.sendpatchset@schroedinger.engr.sgi.com> <20070420110516.GC12075@skynet.ie> <1177095021.10848.18.camel@kleikamp.austin.ibm.com> Content-Type: text/plain Date: Fri, 20 Apr 2007 19:27:01 +0000 Message-Id: <1177097221.10848.31.camel@kleikamp.austin.ibm.com> Mime-Version: 1.0 X-Mailer: Evolution 2.8.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2007-04-20 at 12:10 -0700, Christoph Lameter wrote: > On Fri, 20 Apr 2007, Dave Kleikamp wrote: > > Yeah. I'm working on patches for storing file tails in buffers > > allocated from the slab cache, and the tail will be represented by a > > fake struct page. (This is primarily for kernels with a larger page > > size). So my version of page_cache_size(page) may return a different > > size for different pages belonging to the same mapping. I'm in the > > midst of cleaning up the patches and plan to post them to linux-mm by > > Monday. > > I am not sure what the point of that patchset would be in this context > given that this is about support for arbitrary page sizes. If the > filesystem wants it then it can reduce the page size for small files. > > Different page sizes for one mapping may introduce high complexity into a > filesystem. I'm trying to keep it from getting too complicated. > And we can already represent different page size. We have compound pages > support in the kernel. There are advantages to having a larger base page size, such as increased TLB reach. I'm specifically targetting kernels built with CONFIG_PPC_64K_PAGES, but other architectures could benefit. > page_cache_size(page) in terms of current code in mm is > > PAGE_SIZE << compound_order(page) I don't see page_cache_size() in linux-2.6.21-rc6-mm1. Is there something newer? Anyway, my patches are at a proof-of-concept stage. I look forward to more discussion when I post the patch set. Thanks, Shaggy -- David Kleikamp IBM Linux Technology Center