From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id 9A4936B00A7 for ; Wed, 17 Mar 2010 07:33:46 -0400 (EDT) Date: Wed, 17 Mar 2010 11:33:26 +0000 From: Mel Gorman Subject: Re: [PATCH 06/11] Export fragmentation index via /proc/extfrag_index Message-ID: <20100317113326.GD12388@csn.ul.ie> References: <1268412087-13536-1-git-send-email-mel@csn.ul.ie> <1268412087-13536-7-git-send-email-mel@csn.ul.ie> <20100317114321.4C9A.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20100317114321.4C9A.A69D9226@jp.fujitsu.com> Sender: owner-linux-mm@kvack.org To: KOSAKI Motohiro Cc: Andrew Morton , Andrea Arcangeli , Christoph Lameter , Adam Litke , Avi Kivity , David Rientjes , Rik van Riel , linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: On Wed, Mar 17, 2010 at 11:49:49AM +0900, KOSAKI Motohiro wrote: > > +/* > > + * A fragmentation index only makes sense if an allocation of a requested > > + * size would fail. If that is true, the fragmentation index indicates > > + * whether external fragmentation or a lack of memory was the problem. > > + * The value can be used to determine if page reclaim or compaction > > + * should be used > > + */ > > +int fragmentation_index(unsigned int order, struct contig_page_info *info) > > +{ > > + unsigned long requested = 1UL << order; > > + > > + if (!info->free_blocks_total) > > + return 0; > > + > > + /* Fragmentation index only makes sense when a request would fail */ > > + if (info->free_blocks_suitable) > > + return -1000; > > + > > + /* > > + * Index is between 0 and 1 so return within 3 decimal places > > + * > > + * 0 => allocation would fail due to lack of memory > > + * 1 => allocation would fail due to fragmentation > > + */ > > + return 1000 - ( (1000+(info->free_pages * 1000 / requested)) / info->free_blocks_total); > > +} > > Dumb question. > > your paper (http://portal.acm.org/citation.cfm?id=1375634.1375641) says > > fragmentation_index = 1 - (TotalFree/SizeRequested)/BlocksFree > > but your code have extra '1000+'. Why? To get an approximation to three decimal places. > > Probably, I haven't understand the intention of this calculation. > > > -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org