[RFC PATCH -next 2/7] mm/mglru: make calls to flush_reclaim_state() similar for MGLRU and non-MGLRU

[Chen Ridong <chenridong@huaweicloud.com>]

From: Chen Ridong <chenridong@huawei.com>

Currently, flush_reclaim_state is placed differently between
shrink_node_memcgs and shrink_many. shrink_many (only used for gen-LRU)
calls it after each lruvec is shrunk, while shrink_node_memcgs calls it
only after all lruvecs have been shrunk.

This patch moves flush_reclaim_state into shrink_node_memcgs and calls it
after each lruvec. This unifies the behavior and is reasonable because:

1. flush_reclaim_state adds current->reclaim_state->reclaimed to
   sc->nr_reclaimed.
2. For non-MGLRU root reclaim, this can help stop the iteration earlier
   when nr_to_reclaim is reached.
3. For non-root reclaim, the effect is negligible since flush_reclaim_state
   does nothing in that case.

Signed-off-by: Chen Ridong <chenridong@huawei.com>
---
 mm/vmscan.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 3759cd52c336..5a156ff48520 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -6182,6 +6182,7 @@ static void shrink_node_memcgs(pg_data_t *pgdat, struct scan_control *sc)
 					   sc->nr_scanned - scanned,
 					   sc->nr_reclaimed - reclaimed);
 
+			flush_reclaim_state(sc);
 			/* If partial walks are allowed, bail once goal is reached */
 			if (partial && sc->nr_reclaimed >= sc->nr_to_reclaim) {
 				mem_cgroup_iter_break(target_memcg, memcg);
@@ -6218,8 +6219,6 @@ static void shrink_node(pg_data_t *pgdat, struct scan_control *sc)
 
 	shrink_node_memcgs(pgdat, sc);
 
-	flush_reclaim_state(sc);
-
 	nr_node_reclaimed = sc->nr_reclaimed - nr_reclaimed;
 
 	/* Record the subtree's reclaim efficiency */
-- 
2.34.1