From 6d3163ce86dd386b4f7bda80241d7fea2bc0bb1d Mon Sep 17 00:00:00 2001 From: =?utf8?q?Arve=20Hj=C3=B8nnev=C3=A5g?= Date: Tue, 24 May 2011 17:12:24 -0700 Subject: [PATCH] mm: check if any page in a pageblock is reserved before marking it MIGRATE_RESERVE MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit This fixes a problem where the first pageblock got marked MIGRATE_RESERVE even though it only had a few free pages. eg, On current ARM port, The kernel starts at offset 0x8000 to leave room for boot parameters, and the memory is freed later. This in turn caused no contiguous memory to be reserved and frequent kswapd wakeups that emptied the caches to get more contiguous memory. Unfortunatelly, ARM needs order-2 allocation for pgd (see arm/mm/pgd.c#pgd_alloc()). Therefore the issue is not minor nor easy avoidable. [kosaki.motohiro@jp.fujitsu.com: added some explanation] [kosaki.motohiro@jp.fujitsu.com: add !pfn_valid_within() to check] [minchan.kim@gmail.com: check end_pfn in pageblock_is_reserved] Signed-off-by: John Stultz Signed-off-by: Arve Hjønnevåg Signed-off-by: KOSAKI Motohiro Acked-by: Mel Gorman Acked-by: Dave Hansen Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/page_alloc.c | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 44019da9632e..01e6b614839d 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3328,6 +3328,20 @@ static inline unsigned long wait_table_bits(unsigned long size) #define LONG_ALIGN(x) (((x)+(sizeof(long))-1)&~((sizeof(long))-1)) +/* + * Check if a pageblock contains reserved pages + */ +static int pageblock_is_reserved(unsigned long start_pfn, unsigned long end_pfn) +{ + unsigned long pfn; + + for (pfn = start_pfn; pfn < end_pfn; pfn++) { + if (!pfn_valid_within(pfn) || PageReserved(pfn_to_page(pfn))) + return 1; + } + return 0; +} + /* * Mark a number of pageblocks as MIGRATE_RESERVE. The number * of blocks reserved is based on min_wmark_pages(zone). The memory within @@ -3337,7 +3351,7 @@ static inline unsigned long wait_table_bits(unsigned long size) */ static void setup_zone_migrate_reserve(struct zone *zone) { - unsigned long start_pfn, pfn, end_pfn; + unsigned long start_pfn, pfn, end_pfn, block_end_pfn; struct page *page; unsigned long block_migratetype; int reserve; @@ -3367,7 +3381,8 @@ static void setup_zone_migrate_reserve(struct zone *zone) continue; /* Blocks with reserved pages will never free, skip them. */ - if (PageReserved(page)) + block_end_pfn = min(pfn + pageblock_nr_pages, end_pfn); + if (pageblock_is_reserved(pfn, block_end_pfn)) continue; block_migratetype = get_pageblock_migratetype(page); -- 2.20.1