From: Chen Ridong <chenridong@huawei.com>

The previous patch extended shrink_one to support both lrugen and
non-lrugen reclaim. Now shrink_many and shrink_node_memcgs are almost
identical, except that shrink_many also calls should_abort_scan for lrugen
root reclaim.

This patch adds the should_abort_scan check to shrink_node_memcgs (which is
only meaningful for gen-LRU root reclaim). After this change,
shrink_node_memcgs can be used directly instead of shrink_many, allowing
shrink_many to be safely removed.

Suggested-by: Shakeel Butt <shakeel.butt@linux.dev>
Signed-off-by: Chen Ridong <chenridong@huawei.com>
---
 mm/vmscan.c | 67 ++++++++++++-----------------------------------------
 1 file changed, 15 insertions(+), 52 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 795f5ebd9341..dbf2cfbe3243 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -4758,57 +4758,6 @@ static bool try_to_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
 	return nr_to_scan < 0;
 }
 
-static void shrink_one(struct lruvec *lruvec, struct scan_control *sc);
-
-static void shrink_many(struct pglist_data *pgdat, struct scan_control *sc)
-{
-	struct mem_cgroup *target = sc->target_mem_cgroup;
-	struct mem_cgroup_reclaim_cookie reclaim = {
-		.pgdat = pgdat,
-	};
-	struct mem_cgroup_reclaim_cookie *cookie = &reclaim;
-	struct mem_cgroup *memcg;
-
-	if (current_is_kswapd() || sc->memcg_full_walk)
-		cookie = NULL;
-
-	memcg = mem_cgroup_iter(target, NULL, cookie);
-	while (memcg) {
-		struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat);
-
-		cond_resched();
-
-		mem_cgroup_calculate_protection(target, memcg);
-
-		if (mem_cgroup_below_min(target, memcg))
-			goto next;
-
-		if (mem_cgroup_below_low(target, memcg)) {
-			if (!sc->memcg_low_reclaim) {
-				sc->memcg_low_skipped = 1;
-				goto next;
-			}
-			memcg_memory_event(memcg, MEMCG_LOW);
-		}
-
-		shrink_one(lruvec, sc);
-
-		if (should_abort_scan(lruvec, sc)) {
-			if (cookie)
-				mem_cgroup_iter_break(target, memcg);
-			break;
-		}
-
-next:
-		if (cookie && sc->nr_reclaimed >= sc->nr_to_reclaim) {
-			mem_cgroup_iter_break(target, memcg);
-			break;
-		}
-
-		memcg = mem_cgroup_iter(target, memcg, cookie);
-	}
-}
-
 static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
 {
 	struct blk_plug plug;
@@ -4829,6 +4778,9 @@ static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc
 	blk_finish_plug(&plug);
 }
 
+static void shrink_one(struct lruvec *lruvec, struct scan_control *sc);
+static void shrink_node_memcgs(pg_data_t *pgdat, struct scan_control *sc);
+
 static void lru_gen_shrink_node(struct pglist_data *pgdat, struct scan_control *sc)
 {
 	struct blk_plug plug;
@@ -4858,7 +4810,7 @@ static void lru_gen_shrink_node(struct pglist_data *pgdat, struct scan_control *
 	if (mem_cgroup_disabled())
 		shrink_one(&pgdat->__lruvec, sc);
 	else
-		shrink_many(pgdat, sc);
+		shrink_node_memcgs(pgdat, sc);
 
 	if (current_is_kswapd())
 		sc->nr_reclaimed += reclaimed;
@@ -5554,6 +5506,11 @@ static void lru_gen_shrink_node(struct pglist_data *pgdat, struct scan_control *
 	BUILD_BUG();
 }
 
+static bool should_abort_scan(struct lruvec *lruvec, struct scan_control *sc)
+{
+	return false;
+}
+
 #endif /* CONFIG_LRU_GEN */
 
 static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
@@ -5822,6 +5779,12 @@ static void shrink_node_memcgs(pg_data_t *pgdat, struct scan_control *sc)
 
 		shrink_one(lruvec, sc);
 
+		if (should_abort_scan(lruvec, sc)) {
+			if (partial)
+				mem_cgroup_iter_break(target_memcg, memcg);
+			break;
+		}
+
 		/* 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);
-- 
2.34.1

On Tue, Dec 09, 2025 at 01:25:56AM +0000, Chen Ridong wrote:
> @@ -5822,6 +5779,12 @@ static void shrink_node_memcgs(pg_data_t *pgdat, struct scan_control *sc)
>  
>  		shrink_one(lruvec, sc);
>  
> +		if (should_abort_scan(lruvec, sc)) {

Can you please rename this and add the jump label check?

		if (lru_gen_enabled() && lru_gen_should_abort_scan())

The majority of the checks in there already happen inside
shrink_node_memcgs() itself. Factoring those out is probably better in
another patch, but no need to burden classic LRU in the meantime.

On 2025/12/16 5:17, Johannes Weiner wrote:
> On Tue, Dec 09, 2025 at 01:25:56AM +0000, Chen Ridong wrote:
>> @@ -5822,6 +5779,12 @@ static void shrink_node_memcgs(pg_data_t *pgdat, struct scan_control *sc)
>>  
>>  		shrink_one(lruvec, sc);
>>  
>> +		if (should_abort_scan(lruvec, sc)) {
> 
> Can you please rename this and add the jump label check?
> 
> 		if (lru_gen_enabled() && lru_gen_should_abort_scan())
> 
> The majority of the checks in there already happen inside
> shrink_node_memcgs() itself. Factoring those out is probably better in
> another patch, but no need to burden classic LRU in the meantime.

Thank you very much.

Thank you for the suggestion. lru_gen_should_abort_scan() is indeed a better name, and including the
lru_gen_enabled() check in the condition is necessary.

I'll update the patch accordingly.

-- 
Best regards,
Ridong