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From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: Mel Gorman <mel@csn.ul.ie>
Subject: Re: [PATCH 06/11] Export fragmentation index via /proc/extfrag_index
Cc: kosaki.motohiro@jp.fujitsu.com, Andrew Morton <akpm@linux-foundation.org>,
       Andrea Arcangeli <aarcange@redhat.com>,
       Christoph Lameter <cl@linux-foundation.org>,
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> > > +	/*
> > > +	 * 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.

Do you mean this is poor man's round up logic?
Why don't you use DIV_ROUND_UP? likes following,

return 1000 - (DIV_ROUND_UP(info->free_pages * 1000 / requested) /  info->free_blocks_total);