linux-kernel - Re: [PATCH 30/35] Skip the PCP list search by counting the order and type of pages on list

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Message-ID: <alpine.DEB.1.10.0903161231040.32577@qirst.com>
Date:	Mon, 16 Mar 2009 12:31:44 -0400 (EDT)
From:	Christoph Lameter <cl@...ux-foundation.org>
To:	Mel Gorman <mel@....ul.ie>
cc:	Linux Memory Management List <linux-mm@...ck.org>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Rik van Riel <riel@...hat.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Nick Piggin <npiggin@...e.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Lin Ming <ming.m.lin@...el.com>,
	Zhang Yanmin <yanmin_zhang@...ux.intel.com>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH 30/35] Skip the PCP list search by counting the order
 and type of pages on list

On Mon, 16 Mar 2009, Mel Gorman wrote:

>
>  struct per_cpu_pages {
> -	int count;		/* number of pages in the list */
> +	/* The total number of pages on the PCP lists */
> +	int count;
> +
> +	/* Count of each migratetype and order */
> +	u8 mocount[MIGRATE_PCPTYPES][PAGE_ALLOC_COSTLY_ORDER+1];

What about overflow? You could have more than 255 pages of a given type in
a pcp.

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