From: Huang Ying <ying.huang@xxxxxxxxx> If there is no compound map for a THP (Transparent Huge Page), it is possible that the map count of some sub-pages of the THP is 0. So it is better to split the THP before swapping out. In this way, the sub-pages not mapped will be freed, and we can avoid the unnecessary swap out operations for these sub-pages. Cc: Johannes Weiner <hannes@xxxxxxxxxxx> Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx> --- mm/swap_state.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/mm/swap_state.c b/mm/swap_state.c index 612fb2418df6..528af29327c9 100644 --- a/mm/swap_state.c +++ b/mm/swap_state.c @@ -205,7 +205,9 @@ int add_to_swap(struct page *page, struct list_head *list) /* cannot split, skip it */ if (!can_split_huge_page(page, NULL)) return 0; - huge = true; + /* fallback to split huge page firstly if no PMD map */ + if (compound_mapcount(page)) + huge = true; } #endif -- 2.11.0 -- 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>
