From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932343AbVKVKOa (ORCPT ); Tue, 22 Nov 2005 05:14:30 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932345AbVKVKOa (ORCPT ); Tue, 22 Nov 2005 05:14:30 -0500 Received: from hellhawk.shadowen.org ([80.68.90.175]:31761 "EHLO hellhawk.shadowen.org") by vger.kernel.org with ESMTP id S932343AbVKVKO3 (ORCPT ); Tue, 22 Nov 2005 05:14:29 -0500 Message-ID: <4382EF48.1050107@shadowen.org> Date: Tue, 22 Nov 2005 10:13:28 +0000 From: Andy Whitcroft User-Agent: Debian Thunderbird 1.0.7 (X11/20051017) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Mel Gorman CC: Andi Kleen , linux-mm@kvack.org, mingo@elte.hu, lhms-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, nickpiggin@yahoo.com.au Subject: Re: [PATCH 2/5] Light Fragmentation Avoidance V20: 002_usemap References: <20051115164946.21980.2026.sendpatchset@skynet.csn.ul.ie> <200511160036.54461.ak@suse.de> <200511160252.05494.ak@suse.de> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Mel Gorman wrote: > That's iterating through, potentially, 1024 pages which I considered too > expensive. In terms of code complexity, the page-flags patch adds 237 > which is not much of a saving in comparison to 275 that the usemap > approach uses. Surley you would just use a single bit in the first page of a MAX_ORDER block. We guarentee that the mem_map is contigious out to MAX_ORDER pages so you can simply calculate the offset. The page free path does the same thing to find the buddy pages when coallescing. > Again, I can revisit the page-flag approach if I thought that something > like this would get merged and people would not choke on another page flag > being consumed. All of that said, I am not even sure we have a bit left in the page flags on smaller architectures :/. -apw