From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761198AbXIZTbs (ORCPT ); Wed, 26 Sep 2007 15:31:48 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755938AbXIZTbl (ORCPT ); Wed, 26 Sep 2007 15:31:41 -0400 Received: from extu-mxob-2.symantec.com ([216.10.194.135]:21902 "EHLO extu-mxob-2.symantec.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755186AbXIZTbk (ORCPT ); Wed, 26 Sep 2007 15:31:40 -0400 Date: Wed, 26 Sep 2007 20:31:02 +0100 (BST) From: Hugh Dickins X-X-Sender: hugh@blonde.wat.veritas.com To: KAMEZAWA Hiroyuki cc: clameter@sgi.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, nickpiggin@yahoo.com.au, ricknu-0@student.ltu.se, magnus.damm@gmail.com Subject: Re: [RFC][PATCH] page->mapping clarification [1/3] base functions In-Reply-To: <20070922034234.bdb947e4.kamezawa.hiroyu@jp.fujitsu.com> Message-ID: References: <20070919164308.281f9960.kamezawa.hiroyu@jp.fujitsu.com> <20070921095054.6386bae1.kamezawa.hiroyu@jp.fujitsu.com> <20070922034234.bdb947e4.kamezawa.hiroyu@jp.fujitsu.com> 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 Sat, 22 Sep 2007, KAMEZAWA Hiroyuki wrote: > On Fri, 21 Sep 2007 18:02:47 +0100 (BST) > Hugh Dickins wrote: > > > Or should I now leave PG_swapcache as is, > > given your designs on page->mapping? > > > will conflict with my idea ? > == > http://marc.info/?l=linux-mm&m=118956492926821&w=2 > == I asked because I had thought it would be a serious conflict: obviously the patches as such would conflict quite a bit, but that's not serious, one or the other just gets fixed up. But now I don't see it - we both want to grab a further bit from the low bits of the page->mapping pointer, you PAGE_MAPPING_INFO and me PAGE_MAPPING_SWAP; but that's okay, so long as whoever is left using bit (1<<2) is careful about the 32-bit case and remembers to put __attribute__((aligned(sizeof(long long)))) on the declarations of struct address_space and struct anon_vma and your struct page_mapping_info. Would that waste a little memory? I think not with SLUB, but perhaps with SLOB, which packs a little tighter. Hugh