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Commit 5adc5be7 authored by Mel Gorman's avatar Mel Gorman Committed by Linus Torvalds
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Bias the placement of kernel pages at lower PFNs 



This patch chooses blocks with lower PFNs when placing kernel allocations.
This is particularly important during fallback in low memory situations to
stop unmovable pages being placed throughout the entire address space.

Signed-off-by: default avatarMel Gorman <mel@csn.ul.ie>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 9ef9acb0

mm/page_alloc.c

+20 −0
Original line number Diff line number Diff line
@@ -765,6 +765,23 @@ int move_freepages_block(struct zone *zone, struct page *page, int migratetype) 
	return move_freepages(zone, start_page, end_page, migratetype);

}



/* Return the page with the lowest PFN in the list */

static struct page *min_page(struct list_head *list)

{

	unsigned long min_pfn = -1UL;

	struct page *min_page = NULL, *page;;



	list_for_each_entry(page, list, lru) {

		unsigned long pfn = page_to_pfn(page);

		if (pfn < min_pfn) {

			min_pfn = pfn;

			min_page = page;

		}

	}



	return min_page;

}



/* Remove an element from the buddy allocator from the fallback list */

static struct page *__rmqueue_fallback(struct zone *zone, int order,

						int start_migratetype)
@@ -795,8 +812,11 @@ retry: 
			if (list_empty(&area->free_list[migratetype]))

				continue;



			/* Bias kernel allocations towards low pfns */

			page = list_entry(area->free_list[migratetype].next,

					struct page, lru);

			if (unlikely(start_migratetype != MIGRATE_MOVABLE))

				page = min_page(&area->free_list[migratetype]);

			area->nr_free--;



			/*