diff options
| -rw-r--r-- | mm/page_alloc.c | 53 |
1 files changed, 44 insertions, 9 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index bd65b60939b6..869035717048 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -2216,7 +2216,11 @@ __rmqueue_fallback(struct zone *zone, unsigned int order, int start_migratetype) int fallback_mt; bool can_steal; - /* Find the largest possible block of pages in the other list */ + /* + * Find the largest available free page in the other list. This roughly + * approximates finding the pageblock with the most free pages, which + * would be too costly to do exactly. + */ for (current_order = MAX_ORDER-1; current_order >= order && current_order <= MAX_ORDER-1; --current_order) { @@ -2226,19 +2230,50 @@ __rmqueue_fallback(struct zone *zone, unsigned int order, int start_migratetype) if (fallback_mt == -1) continue; - page = list_first_entry(&area->free_list[fallback_mt], - struct page, lru); + /* + * We cannot steal all free pages from the pageblock and the + * requested migratetype is movable. In that case it's better to + * steal and split the smallest available page instead of the + * largest available page, because even if the next movable + * allocation falls back into a different pageblock than this + * one, it won't cause permanent fragmentation. + */ + if (!can_steal && start_migratetype == MIGRATE_MOVABLE + && current_order > order) + goto find_smallest; - steal_suitable_fallback(zone, page, start_migratetype, - can_steal); + goto do_steal; + } - trace_mm_page_alloc_extfrag(page, order, current_order, - start_migratetype, fallback_mt); + return false; - return true; +find_smallest: + for (current_order = order; current_order < MAX_ORDER; + current_order++) { + area = &(zone->free_area[current_order]); + fallback_mt = find_suitable_fallback(area, current_order, + start_migratetype, false, &can_steal); + if (fallback_mt != -1) + break; } - return false; + /* + * This should not happen - we already found a suitable fallback + * when looking for the largest page. + */ + VM_BUG_ON(current_order == MAX_ORDER); + +do_steal: + page = list_first_entry(&area->free_list[fallback_mt], + struct page, lru); + + steal_suitable_fallback(zone, page, start_migratetype, can_steal); + + trace_mm_page_alloc_extfrag(page, order, current_order, + start_migratetype, fallback_mt); + + return true; + } /* |