[RFC PATCH v3 6/6] mm: mglru: run aging if the preferred type has no folios in reclaimable gens

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

Respect the type selected by positive_ctrl_err(). If there are no
reclaimable generations left for that type, run aging.

For balanced swappiness values near the middle, still allow gentle
reclaim since the swappiness bias is less of a concern, while the
slightly increased aging overhead might become a problem.

Signed-off-by: Barry Song (Xiaomi) <baohua@kernel.org>
---
 mm/vmscan.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 98fd2fac90ac..902d85afc5f6 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -5035,6 +5035,10 @@ static bool should_run_aging(struct lruvec *lruvec, unsigned long max_seq,
 	if (evictable_min_seq(min_seq, swappiness) + MIN_NR_GENS > max_seq)
 		return true;
 
+	/* run aging if the preferred type is exhausted for extreme swappiness */
+	if (min_seq[type] + MIN_NR_GENS > max_seq && !swappiness_is_balanced(swappiness))
+		return true;
+
 	/* try to avoid aging, do gentle reclaim at the default priority */
 	if (sc->priority == DEF_PRIORITY)
 		return false;
-- 
2.34.1