Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756155Ab0BPIvO (ORCPT ); Tue, 16 Feb 2010 03:51:14 -0500 Received: from gir.skynet.ie ([193.1.99.77]:33770 "EHLO gir.skynet.ie" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755492Ab0BPIvN (ORCPT ); Tue, 16 Feb 2010 03:51:13 -0500 Date: Tue, 16 Feb 2010 08:50:59 +0000 From: Mel Gorman To: KOSAKI Motohiro Cc: Andrea Arcangeli , Christoph Lameter , Adam Litke , Avi Kivity , David Rientjes , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 03/12] Export unusable free space index via /proc/pagetypeinfo Message-ID: <20100216085058.GD26086@csn.ul.ie> References: <20100216152106.72FA.A69D9226@jp.fujitsu.com> <20100216083612.GA26086@csn.ul.ie> <20100216173832.730F.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20100216173832.730F.A69D9226@jp.fujitsu.com> User-Agent: Mutt/1.5.17+20080114 (2008-01-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2206 Lines: 46 On Tue, Feb 16, 2010 at 05:41:39PM +0900, KOSAKI Motohiro wrote: > > On Tue, Feb 16, 2010 at 04:03:29PM +0900, KOSAKI Motohiro wrote: > > > > Unusuable free space index is a measure of external fragmentation that > > > > takes the allocation size into account. For the most part, the huge page > > > > size will be the size of interest but not necessarily so it is exported > > > > on a per-order and per-zone basis via /proc/pagetypeinfo. > > > > > > Hmmm.. > > > /proc/pagetype have a machine unfriendly format. perhaps, some user have own ugly > > > /proc/pagetype parser. It have a little risk to break userland ABI. > > > > > > > It's very low risk. I doubt there are machine parsers of > > /proc/pagetypeinfo because there are very few machine-orientated actions > > that can be taken based on the information. It's more informational for > > a user if they were investigating fragmentation problems. > > > > > I have dumb question. Why can't we use another file? > > > > I could. What do you suggest? > > I agree it's low risk. but personally I hope fragmentation ABI keep very stable because > I expect some person makes userland compaction daemon. (read fragmentation index > from /proc and write /proc/compact_memory if necessary). > then, if possible, I hope fragmentation info have individual /proc file. > I'd be somewhat surprised if there was an active userland compaction daemon because I'd expect them to be depending on direct compaction. Userspace compaction is more likely to be an all-or-nothing affair and confined to NUMA nodes if they are being used as containers. If a compaction daemon was to exist, I'd have expected it to be in-kernel because the triggers from userspace are so coarse. Still, I can break out the indices into separate files to cover all the bases. -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab -- 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/