diff options
| -rw-r--r-- | mm/page_alloc.c | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index e29a6ba050c8..f6005b7c3446 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1063,6 +1063,15 @@ static bool bulkfree_pcp_prepare(struct page *page) } #endif /* CONFIG_DEBUG_VM */ +static inline void prefetch_buddy(struct page *page) +{ + unsigned long pfn = page_to_pfn(page); + unsigned long buddy_pfn = __find_buddy_pfn(pfn, 0); + struct page *buddy = page + (buddy_pfn - pfn); + + prefetch(buddy); +} + /* * Frees a number of pages from the PCP lists * Assumes all pages on list are in same zone, and of same order. @@ -1079,6 +1088,7 @@ static void free_pcppages_bulk(struct zone *zone, int count, { int migratetype = 0; int batch_free = 0; + int prefetch_nr = 0; bool isolated_pageblocks; struct page *page, *tmp; LIST_HEAD(head); @@ -1114,6 +1124,18 @@ static void free_pcppages_bulk(struct zone *zone, int count, continue; list_add_tail(&page->lru, &head); + + /* + * We are going to put the page back to the global + * pool, prefetch its buddy to speed up later access + * under zone->lock. It is believed the overhead of + * an additional test and calculating buddy_pfn here + * can be offset by reduced memory latency later. To + * avoid excessive prefetching due to large count, only + * prefetch buddy for the first pcp->batch nr of pages. + */ + if (prefetch_nr++ < pcp->batch) + prefetch_buddy(page); } while (--count && --batch_free && !list_empty(list)); } |