From 5adc5be7cd1bcef6bb64f5255d2a33f20a3cf5be Mon Sep 17 00:00:00 2001 From: Mel Gorman Date: Tue, 16 Oct 2007 01:25:54 -0700 Subject: [PATCH] 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: Mel Gorman Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/page_alloc.c | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 676aec93d6..e1d87ee1d9 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -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--; /* -- 2.39.5