[PATCH 04/12] mm/swap: skip scanning cluster range if it's empty cluster

[Baoquan He]

Since ci->lock has been taken when isolating cluster from
si->free_clusters or taking si->percpu_cluster->next[order],
it's unnecessary to scan and check the cluster range availability
if i'ts empty cluster, and this can accelerate the huge page
swapping.

Signed-off-by: Baoquan He <bhe@xxxxxxxxxx>
---
 mm/swapfile.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 9c9a4ec6d4c6..61efde853eea 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -729,6 +729,9 @@ static bool cluster_scan_range(struct swap_info_struct *si,
 	unsigned long offset, end = start + nr_pages;
 	unsigned char *map = si->swap_map;
 
+	if (cluster_is_empty(ci))
+		return true;
+
 	for (offset = start; offset < end; offset++) {
 		switch (READ_ONCE(map[offset])) {
 		case 0:
-- 
2.41.0