Revert "Bias the placement of kernel pages at lower PFNs"
This reverts commit 5adc5be7cd1bcef6bb64f5255d2a33f20a3cf5be.
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: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index da69d83..12376ae 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -749,23 +749,6 @@
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 @@
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--;
/*