[PATCH v5] mm: multi-gen LRU: reuse some legacy trace events

[Jaewon Kim <jaewon31.kim@xxxxxxxxxxx>]

As the legacy lru provides, the mglru needs some trace events for
debugging. Let's reuse following legacy events for the mglru.

  trace_mm_vmscan_lru_isolate
  trace_mm_vmscan_lru_shrink_inactive

Here's an example
  mm_vmscan_lru_isolate: classzone=2 order=0 nr_requested=4096 nr_scanned=64 nr_skipped=0 nr_taken=64 lru=inactive_file
  mm_vmscan_lru_shrink_inactive: nid=0 nr_scanned=64 nr_reclaimed=63 nr_dirty=0 nr_writeback=0 nr_congested=0 nr_immediate=0 nr_activate_anon=0 nr_activate_file=1 nr_ref_keep=0 nr_unmap_fail=0 priority=2 flags=RECLAIM_WB_FILE|RECLAIM_WB_ASYNC

Signed-off-by: Jaewon Kim <jaewon31.kim@xxxxxxxxxxx>
Acked-by: Yu Zhao <yuzhao@xxxxxxxxxx>
---
v5: reuse the legacy trace events
v4: wrap with #ifdef CONFIG_LRU_GEN
v3: change printk format
v2: use condition and make it aligned
v1: introduce trace events
---
 mm/vmscan.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 6f13394b112e..3f963f3616ea 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -5005,6 +5005,7 @@ static int scan_folios(struct lruvec *lruvec, struct scan_control *sc,
 	int sorted = 0;
 	int scanned = 0;
 	int isolated = 0;
+	int skipped = 0;
 	int remaining = MAX_LRU_BATCH;
 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
 	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
@@ -5018,7 +5019,7 @@ static int scan_folios(struct lruvec *lruvec, struct scan_control *sc,
 
 	for (i = MAX_NR_ZONES; i > 0; i--) {
 		LIST_HEAD(moved);
-		int skipped = 0;
+		int skipped_zone = 0;
 		int zone = (sc->reclaim_idx + i) % MAX_NR_ZONES;
 		struct list_head *head = &lrugen->folios[gen][type][zone];
 
@@ -5040,16 +5041,17 @@ static int scan_folios(struct lruvec *lruvec, struct scan_control *sc,
 				isolated += delta;
 			} else {
 				list_move(&folio->lru, &moved);
-				skipped += delta;
+				skipped_zone += delta;
 			}
 
-			if (!--remaining || max(isolated, skipped) >= MIN_LRU_BATCH)
+			if (!--remaining || max(isolated, skipped_zone) >= MIN_LRU_BATCH)
 				break;
 		}
 
-		if (skipped) {
+		if (skipped_zone) {
 			list_splice(&moved, head);
-			__count_zid_vm_events(PGSCAN_SKIP, zone, skipped);
+			__count_zid_vm_events(PGSCAN_SKIP, zone, skipped_zone);
+			skipped += skipped_zone;
 		}
 
 		if (!remaining || isolated >= MIN_LRU_BATCH)
@@ -5064,6 +5066,9 @@ static int scan_folios(struct lruvec *lruvec, struct scan_control *sc,
 	__count_memcg_events(memcg, item, isolated);
 	__count_memcg_events(memcg, PGREFILL, sorted);
 	__count_vm_events(PGSCAN_ANON + type, isolated);
+	trace_mm_vmscan_lru_isolate(sc->reclaim_idx, sc->order, MAX_LRU_BATCH,
+				scanned, skipped, isolated,
+				type ? LRU_INACTIVE_FILE : LRU_INACTIVE_ANON);
 
 	/*
 	 * There might not be eligible folios due to reclaim_idx. Check the
@@ -5194,6 +5199,9 @@ static int evict_folios(struct lruvec *lruvec, struct scan_control *sc, int swap
 retry:
 	reclaimed = shrink_folio_list(&list, pgdat, sc, &stat, false);
 	sc->nr_reclaimed += reclaimed;
+	trace_mm_vmscan_lru_shrink_inactive(pgdat->node_id,
+			scanned, reclaimed, &stat, sc->priority,
+			type ? LRU_INACTIVE_FILE : LRU_INACTIVE_ANON);
 
 	list_for_each_entry_safe_reverse(folio, next, &list, lru) {
 		if (!folio_evictable(folio)) {
-- 
2.17.1