On Fri, Jan 18, 2019 at 02:40:00PM +0100, Vlastimil Babka wrote: > > Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> > > Great, you crossed off this old TODO item, and didn't need pageblock isolation > to do that :D > The TODO is not just old, it's ancient! The idea of capture was first floated in 2008! A version was proposed at https://lwn.net/Articles/301246/ against 2.6.27-rc1-mm1. > I have just one worry... > > > @@ -837,6 +873,12 @@ static inline void __free_one_page(struct page *page, > > > > continue_merging: > > while (order < max_order - 1) { > > + if (compaction_capture(capc, page, order)) { > > + if (likely(!is_migrate_isolate(migratetype))) > > + __mod_zone_freepage_state(zone, -(1 << order), > > + migratetype); > > + return; > > What about MIGRATE_CMA pageblocks and compaction for non-movable allocation, > won't that violate CMA expecteations? > And less critically, this will avoid the migratetype stealing decisions and > actions, potentially resulting in worse fragmentation avoidance? > Both might be issues. How about this (untested)? diff --git a/mm/page_alloc.c b/mm/page_alloc.c index fe089ac8a207..d61174bb0333 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -799,11 +799,26 @@ static inline struct capture_control *task_capc(struct zone *zone) } static inline bool -compaction_capture(struct capture_control *capc, struct page *page, int order) +compaction_capture(struct capture_control *capc, struct page *page, + int order, int migratetype) { if (!capc || order != capc->cc->order) return false; + /* Do not accidentally pollute CMA or isolated regions*/ + if (is_migrate_cma(migratetype) || + is_migrate_isolate(migratetype)) + return false; + + /* + * Do not let lower order allocations polluate a movable pageblock. + * This might let an unmovable request use a reclaimable pageblock + * and vice-versa but no more than normal fallback logic which can + * have trouble finding a high-order free page. + */ + if (order < pageblock_order && migratetype == MIGRATE_MOVABLE) + return false; + capc->page = page; return true; } @@ -815,7 +830,8 @@ static inline struct capture_control *task_capc(struct zone *zone) } static inline bool -compaction_capture(struct capture_control *capc, struct page *page, int order) +compaction_capture(struct capture_control *capc, struct page *page, + int order, int migratetype) { return false; } @@ -870,7 +886,7 @@ static inline void __free_one_page(struct page *page, continue_merging: while (order < max_order - 1) { - if (compaction_capture(capc, page, order)) { + if (compaction_capture(capc, page, order, migratetype)) { if (likely(!is_migrate_isolate(migratetype))) __mod_zone_freepage_state(zone, -(1 << order), migratetype); -- Mel Gorman SUSE Labs
