From e984bb43f7450312ba66fe0e67a99efa6be3b246 Mon Sep 17 00:00:00 2001 From: Bob Picco Date: Sat, 20 May 2006 15:00:31 -0700 Subject: [PATCH] [PATCH] Align the node_mem_map endpoints to a MAX_ORDER boundary Andy added code to buddy allocator which does not require the zone's endpoints to be aligned to MAX_ORDER. An issue is that the buddy allocator requires the node_mem_map's endpoints to be MAX_ORDER aligned. Otherwise __page_find_buddy could compute a buddy not in node_mem_map for partial MAX_ORDER regions at zone's endpoints. page_is_buddy will detect that these pages at endpoints are not PG_buddy (they were zeroed out by bootmem allocator and not part of zone). Of course the negative here is we could waste a little memory but the positive is eliminating all the old checks for zone boundary conditions. SPARSEMEM won't encounter this issue because of MAX_ORDER size constraint when SPARSEMEM is configured. ia64 VIRTUAL_MEM_MAP doesn't need the logic either because the holes and endpoints are handled differently. This leaves checking alloc_remap and other arches which privately allocate for node_mem_map. Signed-off-by: Bob Picco Acked-by: Mel Gorman Cc: Dave Hansen Cc: Andy Whitcroft Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/mmzone.h | 1 + mm/page_alloc.c | 14 +++++++++++--- 2 files changed, 12 insertions(+), 3 deletions(-) diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index b5c21122c299..36740354d4db 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -22,6 +22,7 @@ #else #define MAX_ORDER CONFIG_FORCE_MAX_ZONEORDER #endif +#define MAX_ORDER_NR_PAGES (1 << (MAX_ORDER - 1)) struct free_area { struct list_head free_list; diff --git a/mm/page_alloc.c b/mm/page_alloc.c index bb3416932ab0..253a450c400d 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -2125,14 +2125,22 @@ static void __init alloc_node_mem_map(struct pglist_data *pgdat) #ifdef CONFIG_FLAT_NODE_MEM_MAP /* ia64 gets its own node_mem_map, before this, without bootmem */ if (!pgdat->node_mem_map) { - unsigned long size; + unsigned long size, start, end; struct page *map; - size = (pgdat->node_spanned_pages + 1) * sizeof(struct page); + /* + * The zone's endpoints aren't required to be MAX_ORDER + * aligned but the node_mem_map endpoints must be in order + * for the buddy allocator to function correctly. + */ + start = pgdat->node_start_pfn & ~(MAX_ORDER_NR_PAGES - 1); + end = pgdat->node_start_pfn + pgdat->node_spanned_pages; + end = ALIGN(end, MAX_ORDER_NR_PAGES); + size = (end - start) * sizeof(struct page); map = alloc_remap(pgdat->node_id, size); if (!map) map = alloc_bootmem_node(pgdat, size); - pgdat->node_mem_map = map; + pgdat->node_mem_map = map + (pgdat->node_start_pfn - start); } #ifdef CONFIG_FLATMEM /* -- 2.20.1