mm: keep separate anon and file statistics on page reclaim activity

Having statistics on pages scanned and pages reclaimed for both anon and
file pages makes it easier to evaluate changes to LRU balancing.

While at it, clean up the stat-keeping mess for isolation, putback,
reclaim stats etc.  a bit: first the physical LRU operation (isolation and
putback), followed by vmstats, reclaim_stats, and then vm events.
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Rik van Riel <riel@surriel.com>
Link: http://lkml.kernel.org/r/20200520232525.798933-3-hannes@cmpxchg.orgSigned-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/vm_event_item.h

@@ -35,6 +35,10 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
 		PGSCAN_KSWAPD,
 		PGSCAN_DIRECT,
 		PGSCAN_DIRECT_THROTTLE,
+		PGSCAN_ANON,
+		PGSCAN_FILE,
+		PGSTEAL_ANON,
+		PGSTEAL_FILE,
 #ifdef CONFIG_NUMA
 		PGSCAN_ZONE_RECLAIM_FAILED,
 #endif

mm/vmscan.c

@@ -1913,7 +1913,7 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
 	unsigned int nr_reclaimed = 0;
 	unsigned long nr_taken;
 	struct reclaim_stat stat;
-	int file = is_file_lru(lru);
+	bool file = is_file_lru(lru);
 	enum vm_event_item item;
 	struct pglist_data *pgdat = lruvec_pgdat(lruvec);
 	struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
@@ -1941,11 +1941,12 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
 
 	__mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, nr_taken);
 	reclaim_stat->recent_scanned[file] += nr_taken;
-
 	item = current_is_kswapd() ? PGSCAN_KSWAPD : PGSCAN_DIRECT;
 	if (!cgroup_reclaim(sc))
 		__count_vm_events(item, nr_scanned);
 	__count_memcg_events(lruvec_memcg(lruvec), item, nr_scanned);
+	__count_vm_events(PGSCAN_ANON + file, nr_scanned);
+
 	spin_unlock_irq(&pgdat->lru_lock);
 
 	if (nr_taken == 0)
@@ -1956,16 +1957,16 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
 
 	spin_lock_irq(&pgdat->lru_lock);
 
+	move_pages_to_lru(lruvec, &page_list);
+
+	__mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken);
+	reclaim_stat->recent_rotated[0] += stat.nr_activate[0];
+	reclaim_stat->recent_rotated[1] += stat.nr_activate[1];
 	item = current_is_kswapd() ? PGSTEAL_KSWAPD : PGSTEAL_DIRECT;
 	if (!cgroup_reclaim(sc))
 		__count_vm_events(item, nr_reclaimed);
 	__count_memcg_events(lruvec_memcg(lruvec), item, nr_reclaimed);
-	reclaim_stat->recent_rotated[0] += stat.nr_activate[0];
-	reclaim_stat->recent_rotated[1] += stat.nr_activate[1];
-
-	move_pages_to_lru(lruvec, &page_list);
-
-	__mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken);
+	__count_vm_events(PGSTEAL_ANON + file, nr_reclaimed);
 
 	spin_unlock_irq(&pgdat->lru_lock);
 

mm/vmstat.c

@@ -1203,6 +1203,10 @@ const char * const vmstat_text[] = {
 	"pgscan_kswapd",
 	"pgscan_direct",
 	"pgscan_direct_throttle",
+	"pgscan_anon",
+	"pgscan_file",
+	"pgsteal_anon",
+	"pgsteal_file",
 
 #ifdef CONFIG_NUMA
 	"zone_reclaim_failed",