Commit 44048d70 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Revert "Bias the placement of kernel pages at lower PFNs" 



This reverts commit 5adc5be7.

Alexey Dobriyan reports that it causes huge slowdowns under some loads,
in his case a "mkfs.ext2" on a 30G partition.  With the placement bias,
the mkfs took over four minutes, with it reverted it's back to about ten
seconds for Alexey.

Reported-and-tested-by: default avatarAlexey Dobriyan <adobriyan@gmail.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent e6a5c27f

mm/page_alloc.c

+0 −20
Original line number Diff line number Diff line
@@ -749,23 +749,6 @@ 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)
@@ -789,11 +772,8 @@ static struct page *__rmqueue_fallback(struct zone *zone, int order, 
			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--;



			/*

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