In move_to_free_list(), when a page block changes its migration type, we need to update free page counts for both the old and new types. Originally, this was done by two calls to account_freepages(), which updates NR_FREE_PAGES and also type-specific counters. However, this causes NR_FREE_PAGES to be updated twice, while the net change is zero in most cases. This patch introduces a new function account_freepages_both() that updates the statistics for both old and new migration types in one go. It avoids the double update of NR_FREE_PAGES by computing the net change only when the isolation status changes. The optimization avoid duplicate NR_FREE_PAGES updates in move_to_free_list(). Signed-off-by: Yajun Deng --- mm/page_alloc.c | 37 ++++++++++++++++++++++++++++++------- 1 file changed, 30 insertions(+), 7 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index ebfa07632995..e51d8bd7ab7d 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -812,6 +812,16 @@ compaction_capture(struct capture_control *capc, struct page *page, } #endif /* CONFIG_COMPACTION */ +static inline void account_specific_freepages(struct zone *zone, int nr_pages, + int migratetype) +{ + if (is_migrate_cma(migratetype)) + __mod_zone_page_state(zone, NR_FREE_CMA_PAGES, nr_pages); + else if (migratetype == MIGRATE_HIGHATOMIC) + WRITE_ONCE(zone->nr_free_highatomic, + zone->nr_free_highatomic + nr_pages); +} + static inline void account_freepages(struct zone *zone, int nr_pages, int migratetype) { @@ -822,11 +832,25 @@ static inline void account_freepages(struct zone *zone, int nr_pages, __mod_zone_page_state(zone, NR_FREE_PAGES, nr_pages); - if (is_migrate_cma(migratetype)) - __mod_zone_page_state(zone, NR_FREE_CMA_PAGES, nr_pages); - else if (migratetype == MIGRATE_HIGHATOMIC) - WRITE_ONCE(zone->nr_free_highatomic, - zone->nr_free_highatomic + nr_pages); + account_specific_freepages(zone, nr_pages, migratetype); +} + +static inline void account_freepages_both(struct zone *zone, int nr_pages, + int old_mt, int new_mt) +{ + lockdep_assert_held(&zone->lock); + + bool old_isolated = is_migrate_isolate(old_mt); + bool new_isolated = is_migrate_isolate(new_mt); + + if (old_isolated != new_isolated) + __mod_zone_page_state(zone, NR_FREE_PAGES, + old_isolated ? nr_pages : -nr_pages); + + if (!old_isolated) + account_specific_freepages(zone, -nr_pages, old_mt); + if (!new_isolated) + account_specific_freepages(zone, nr_pages, new_mt); } /* Used for pages not on another list */ @@ -869,8 +893,7 @@ static inline void move_to_free_list(struct page *page, struct zone *zone, list_move_tail(&page->buddy_list, &area->free_list[new_mt]); - account_freepages(zone, -nr_pages, old_mt); - account_freepages(zone, nr_pages, new_mt); + account_freepages_both(zone, nr_pages, old_mt, new_mt); if (order >= pageblock_order && is_migrate_isolate(old_mt) != is_migrate_isolate(new_mt)) { -- 2.34.1