[PATCH] mm: page_alloc: increase size of per-cpu-pages

	/*

	 * The per-cpu-pages pools are set to around 1000th of the

	 * size of the zone.  But no more than 1/4 of a meg - there's

	 * no point in going beyond the size of L2 cache.

	 * size of the zone.  But no more than 1/2 of a meg.

	 *

	 * OK, so we don't know how big the cache is.  So guess.

	 */

	batch = zone->present_pages / 1024;

	if (batch * PAGE_SIZE > 256 * 1024)

		batch = (256 * 1024) / PAGE_SIZE;

	if (batch * PAGE_SIZE > 512 * 1024)

		batch = (512 * 1024) / PAGE_SIZE;

	batch /= 4;		/* We effectively *= 4 below */

	if (batch < 1)

		batch = 1;

	/*

	 * 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.

	 * We will be trying to allcoate bigger chunks of contiguous

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

	 * better cache coloring.

	 *

	 * 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.

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

	 */

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

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

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

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

	return batch;

}