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Commit 0ceaacc9 authored by Nick Piggin's avatar Nick Piggin Committed by Linus Torvalds
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[PATCH] Fix up per-cpu page batch sizes 



The code to clamp batch sizes to 2^n - 1 went missing and an extra
check got added, which must have been a hunk of the "higer order pcp
batch refills" work sneaking in.

Signed-off-by: default avatarNick Piggin <npiggin@suse.de>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 9a405257

mm/page_alloc.c

+8 −8
Original line number Diff line number Diff line
@@ -1772,16 +1772,16 @@ static int __devinit zone_batchsize(struct zone *zone) 
		batch = 1;



	/*

	 * We will be trying to allcoate bigger chunks of contiguous

	 * memory of the order of fls(batch).  This should result in

	 * better cache coloring.

	 * Clamp the batch to a 2^n - 1 value. Having a power

	 * of 2 value was found to be more likely to have

	 * suboptimal cache aliasing properties in some cases.

	 *

	 * A sanity check also to ensure that batch is still in limits.

	 * For example if 2 tasks are alternately allocating

	 * batches of pages, one task can end up with a lot

	 * of pages of one half of the possible page colors

	 * and the other with pages of the other colors.

	 */

	batch = (1 << fls(batch + batch/2));



	if (fls(batch) >= (PAGE_SHIFT + MAX_ORDER - 2))

		batch = PAGE_SHIFT + ((MAX_ORDER - 1 - PAGE_SHIFT)/2);

	batch = (1 << (fls(batch + batch/2)-1)) - 1;



	return batch;

}