linux-kernel - Re: [PATCH 05/11] Export unusable free space index via /proc/unusable

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Message-ID: <alpine.DEB.2.00.1003231229310.10178@router.home>
Date:	Tue, 23 Mar 2010 12:31:35 -0500 (CDT)
From:	Christoph Lameter <cl@...ux-foundation.org>
To:	Mel Gorman <mel@....ul.ie>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Adam Litke <agl@...ibm.com>, Avi Kivity <avi@...hat.com>,
	David Rientjes <rientjes@...gle.com>,
	Minchan Kim <minchan.kim@...il.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Rik van Riel <riel@...hat.com>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [PATCH 05/11] Export unusable free space index via
 /proc/unusable_index

On Tue, 23 Mar 2010, Mel Gorman wrote:

> +/*
> + * Return an index indicating how much of the available free memory is
> + * unusable for an allocation of the requested size.
> + */
> +static int unusable_free_index(unsigned int order,
> +				struct contig_page_info *info)
> +{
> +	/* No free memory is interpreted as all free memory is unusable */
> +	if (info->free_pages == 0)
> +		return 1000;


Is that assumption correct? If you have no free memory then you do not
know about the fragmentation status that would result if you would run
reclaim and free some memory. Going into a compaction mode would not be
useful. Should this not return 0 to avoid any compaction run when all
memory is allocated?

Otherwise

Reviewed-by: Christoph Lameter <cl@...ux-foundation.org>

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