[RFC PATCH v4 16/16] mm/mglru: reduce folios pulled from the oldest gen in inc_min_seq()

["Barry Song (Xiaomi)" <baohua@kernel.org>]

Pulling folios from the oldest generation to the second-oldest
generation with MAX_LRU_BATCH can take a long time, as the spinlock
is held throughout the operation and blocks other users.

Reduce the remaining batch size significantly. This reduces the lock
hold time, allowing concurrent reclaim, lru_cache_drain, and other
operations to make progress.

Signed-off-by: Barry Song (Xiaomi) <baohua@kernel.org>
---
 mm/vmscan.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index c0350a8b61d1..8e6fcefe0353 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -3945,7 +3945,7 @@ static inline void flush_lru_batch(struct list_head *head, struct list_head **ba
 static bool inc_min_seq(struct lruvec *lruvec, int type, int swappiness)
 {
 	int zone;
-	int remaining = MAX_LRU_BATCH;
+	int remaining = MAX_LRU_BATCH / (is_extreme_swappiness(swappiness) ? 2 : 8);
 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
 	int hist = lru_hist_from_seq(lrugen->min_seq[type]);
 	int new_gen, old_gen = lru_gen_from_seq(lrugen->min_seq[type]);
-- 
2.34.1