Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760098AbXETEKj (ORCPT ); Sun, 20 May 2007 00:10:39 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756467AbXETEKa (ORCPT ); Sun, 20 May 2007 00:10:30 -0400 Received: from gw1.cosmosbay.com ([86.65.150.130]:38038 "EHLO gw1.cosmosbay.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756256AbXETEKa (ORCPT ); Sun, 20 May 2007 00:10:30 -0400 Message-ID: <464FCA28.9040009@cosmosbay.com> Date: Sun, 20 May 2007 06:10:16 +0200 From: Eric Dumazet User-Agent: Thunderbird 1.5.0.10 (Windows/20070221) MIME-Version: 1.0 To: Christoph Lameter CC: William Lee Irwin III , Nick Piggin , Linux Kernel Mailing List , Linux Memory Management List , linux-arch@vger.kernel.org, Andi Kleen Subject: Re: [rfc] increase struct page size?! References: <20070518040854.GA15654@wotan.suse.de> <20070519012530.GB15569@wotan.suse.de> <20070519181501.GC19966@holomorphy.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 8bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-1.6 (gw1.cosmosbay.com [86.65.150.130]); Sun, 20 May 2007 06:10:22 +0200 (CEST) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1108 Lines: 24 Christoph Lameter a ?crit : > On Sat, 19 May 2007, William Lee Irwin III wrote: > >> However, there are numerous optimizations and features made possible >> with flag bits, which might as could be made cheap by padding struct >> page up to the next highest power of 2 bytes with space for flag bits. > > Well the last time I tried to get this by Andi we became a bit concerned > when we realized that the memory map would grow by 14% in size. Given > that 4k page size challenged platforms have a huge amount of page structs > that growth is significant. I think it would be fine to do it for IA64 > with 16k page size but not for x86_64. This reminds me Andi attempted in the past to convert 'flags' to a 32 bits field : http://marc.info/?l=linux-kernel&m=107903527523739&w=2 I wonder why this idea was not taken, saving 2MB per GB of memory is nice :) - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/