[PATCH v13 135/137] mm/vmscan: Optimise shrink_page_list for smaller THPs

Matthew Wilcox (Oracle)
2021-07-12T04:20:02Z

A THP which is smaller than a PMD does not need to do the extra work
in try_to_unmap() of trying to split a PMD entry.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
mm/vmscan.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 8b17e46dbf32..433956675107 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1496,7 +1496,8 @@ static unsigned int shrink_page_list(struct list_head *page_list,
enum ttu_flags flags = TTU_BATCH_FLUSH;
bool was_swapbacked = PageSwapBacked(page);

- if (unlikely(PageTransHuge(page)))
+ if (PageTransHuge(page) &&
+ thp_order(page) >= HPAGE_PMD_ORDER)
flags |= TTU_SPLIT_HUGE_PMD;

try_to_unmap(page, flags);
--
2.30.2