Now that swap supports storing all mTHP sizes, avoid splitting large folios before swap-out. This benefits performance of the swap-out path by eliding split_folio_to_list(), which is expensive, and also sets us up for swapping in large folios in a future series. If the folio is partially mapped, we continue to split it since we want to avoid the extra IO overhead and storage of writing out pages uneccessarily. Reviewed-by: David Hildenbrand <david@xxxxxxxxxx> Reviewed-by: Barry Song <v-songbaohua@xxxxxxxx> Signed-off-by: Ryan Roberts <ryan.roberts@xxxxxxx> --- mm/vmscan.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 00adaf1cb2c3..293120fe54f3 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1223,11 +1223,12 @@ static unsigned int shrink_folio_list(struct list_head *folio_list, if (!can_split_folio(folio, NULL)) goto activate_locked; /* - * Split folios without a PMD map right - * away. Chances are some or all of the - * tail pages can be freed without IO. + * Split partially mapped folios right + * away. We can free the unmapped pages + * without IO. */ - if (!folio_entire_mapcount(folio) && + if (data_race(!list_empty( + &folio->_deferred_list)) && split_folio_to_list(folio, folio_list)) goto activate_locked; -- 2.25.1
