On 2017/2/11 1:23, Vlastimil Babka wrote: > When stealing pages from pageblock of a different migratetype, we count how > many free pages were stolen, and change the pageblock's migratetype if more > than half of the pageblock was free. This might be too conservative, as there > might be other pages that are not free, but were allocated with the same > migratetype as our allocation requested. > > While we cannot determine the migratetype of allocated pages precisely (at > least without the page_owner functionality enabled), we can count pages that > compaction would try to isolate for migration - those are either on LRU or > __PageMovable(). The rest can be assumed to be MIGRATE_RECLAIMABLE or > MIGRATE_UNMOVABLE, which we cannot easily distinguish. This counting can be > done as part of free page stealing with little additional overhead. > > The page stealing code is changed so that it considers free pages plus pages > of the "good" migratetype for the decision whether to change pageblock's > migratetype. > > The result should be more accurate migratetype of pageblocks wrt the actual > pages in the pageblocks, when stealing from semi-occupied pageblocks. This > should help the efficiency of page grouping by mobility. > > Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx> Hi Vlastimil, How about these two changes? 1. If we steal some free pages, we will add these page at the head of start_migratetype list, it will cause more fixed, because these pages will be allocated more easily. So how about use list_move_tail instead of list_move? __rmqueue_fallback steal_suitable_fallback move_freepages_block move_freepages list_move 2. When doing expand() - list_add(), usually the list is empty, but in the following case, the list is not empty, because we did move_freepages_block() before. __rmqueue_fallback steal_suitable_fallback move_freepages_block // move to the list of start_migratetype expand // split the largest order list_add // add to the list of start_migratetype So how about use list_add_tail instead of list_add? Then we can merge the large block again as soon as the page freed. Thanks, Xishi Qiu -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
