From: Zi Yan <ziy@xxxxxxxxxx> Subject: mm: page_alloc: avoid merging non-fallbackable pageblocks with others This is done in addition to MIGRATE_ISOLATE pageblock merge avoidance. It prepares for the upcoming removal of the MAX_ORDER-1 alignment requirement for CMA and alloc_contig_range(). MIGRATE_HIGHATOMIC should not merge with other migratetypes like MIGRATE_ISOLATE and MIGRARTE_CMA[1], so this commit prevents that too. Remove MIGRATE_CMA and MIGRATE_ISOLATE from fallbacks list, since they are never used. [1] https://lore.kernel.org/linux-mm/20211130100853.GP3366@xxxxxxxxxxxxxxxxxxx/ Link: https://lkml.kernel.org/r/20220124175957.1261961-1-zi.yan@xxxxxxxx Signed-off-by: Zi Yan <ziy@xxxxxxxxxx> Acked-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> Acked-by: David Hildenbrand <david@xxxxxxxxxx> Acked-by: Vlastimil Babka <vbabka@xxxxxxx> Acked-by: Mike Rapoport <rppt@xxxxxxxxxxxxx> Reviewed-by: Oscar Salvador <osalvador@xxxxxxx> Cc: Mike Rapoport <rppt@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/mmzone.h | 11 +++++++++ mm/page_alloc.c | 46 ++++++++++++++++++--------------------- 2 files changed, 33 insertions(+), 24 deletions(-) --- a/include/linux/mmzone.h~mm-page_alloc-avoid-merging-non-fallbackable-pageblocks-with-others +++ a/include/linux/mmzone.h @@ -83,6 +83,17 @@ static inline bool is_migrate_movable(in return is_migrate_cma(mt) || mt == MIGRATE_MOVABLE; } +/* + * Check whether a migratetype can be merged with another migratetype. + * + * It is only mergeable when it can fall back to other migratetypes for + * allocation. See fallbacks[MIGRATE_TYPES][3] in page_alloc.c. + */ +static inline bool migratetype_is_mergeable(int mt) +{ + return mt < MIGRATE_PCPTYPES; +} + #define for_each_migratetype_order(order, type) \ for (order = 0; order < MAX_ORDER; order++) \ for (type = 0; type < MIGRATE_TYPES; type++) --- a/mm/page_alloc.c~mm-page_alloc-avoid-merging-non-fallbackable-pageblocks-with-others +++ a/mm/page_alloc.c @@ -1117,25 +1117,24 @@ continue_merging: } if (order < MAX_ORDER - 1) { /* If we are here, it means order is >= pageblock_order. - * We want to prevent merge between freepages on isolate - * pageblock and normal pageblock. Without this, pageblock - * isolation could cause incorrect freepage or CMA accounting. + * We want to prevent merge between freepages on pageblock + * without fallbacks and normal pageblock. Without this, + * pageblock isolation could cause incorrect freepage or CMA + * accounting or HIGHATOMIC accounting. * * We don't want to hit this code for the more frequent * low-order merging. */ - if (unlikely(has_isolate_pageblock(zone))) { - int buddy_mt; + int buddy_mt; - buddy_pfn = __find_buddy_pfn(pfn, order); - buddy = page + (buddy_pfn - pfn); - buddy_mt = get_pageblock_migratetype(buddy); - - if (migratetype != buddy_mt - && (is_migrate_isolate(migratetype) || - is_migrate_isolate(buddy_mt))) - goto done_merging; - } + buddy_pfn = __find_buddy_pfn(pfn, order); + buddy = page + (buddy_pfn - pfn); + buddy_mt = get_pageblock_migratetype(buddy); + + if (migratetype != buddy_mt + && (!migratetype_is_mergeable(migratetype) || + !migratetype_is_mergeable(buddy_mt))) + goto done_merging; max_order = order + 1; goto continue_merging; } @@ -2479,17 +2478,13 @@ struct page *__rmqueue_smallest(struct z /* * This array describes the order lists are fallen back to when * the free lists for the desirable migrate type are depleted + * + * The other migratetypes do not have fallbacks. */ static int fallbacks[MIGRATE_TYPES][3] = { [MIGRATE_UNMOVABLE] = { MIGRATE_RECLAIMABLE, MIGRATE_MOVABLE, MIGRATE_TYPES }, [MIGRATE_MOVABLE] = { MIGRATE_RECLAIMABLE, MIGRATE_UNMOVABLE, MIGRATE_TYPES }, [MIGRATE_RECLAIMABLE] = { MIGRATE_UNMOVABLE, MIGRATE_MOVABLE, MIGRATE_TYPES }, -#ifdef CONFIG_CMA - [MIGRATE_CMA] = { MIGRATE_TYPES }, /* Never used */ -#endif -#ifdef CONFIG_MEMORY_ISOLATION - [MIGRATE_ISOLATE] = { MIGRATE_TYPES }, /* Never used */ -#endif }; #ifdef CONFIG_CMA @@ -2795,8 +2790,8 @@ static void reserve_highatomic_pageblock /* Yoink! */ mt = get_pageblock_migratetype(page); - if (!is_migrate_highatomic(mt) && !is_migrate_isolate(mt) - && !is_migrate_cma(mt)) { + /* Only reserve normal pageblocks (i.e., they can merge with others) */ + if (migratetype_is_mergeable(mt)) { zone->nr_reserved_highatomic += pageblock_nr_pages; set_pageblock_migratetype(page, MIGRATE_HIGHATOMIC); move_freepages_block(zone, page, MIGRATE_HIGHATOMIC, NULL); @@ -3545,8 +3540,11 @@ int __isolate_free_page(struct page *pag struct page *endpage = page + (1 << order) - 1; for (; page < endpage; page += pageblock_nr_pages) { int mt = get_pageblock_migratetype(page); - if (!is_migrate_isolate(mt) && !is_migrate_cma(mt) - && !is_migrate_highatomic(mt)) + /* + * Only change normal pageblocks (i.e., they can merge + * with others) + */ + if (migratetype_is_mergeable(mt)) set_pageblock_migratetype(page, MIGRATE_MOVABLE); } _
