[v2 PATCH 8/9] mm: vmscan: add page demotion counter

[Yang Shi]

Account the number of demoted pages into reclaim_state->nr_demoted.

Add pgdemote_kswapd and pgdemote_direct VM counters showed in
/proc/vmstat.

Signed-off-by: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx>
---
 include/linux/vm_event_item.h | 2 ++
 include/linux/vmstat.h        | 1 +
 mm/internal.h                 | 1 +
 mm/vmscan.c                   | 7 +++++++
 mm/vmstat.c                   | 2 ++
 5 files changed, 13 insertions(+)

diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h
index 47a3441..499a3aa 100644
--- a/include/linux/vm_event_item.h
+++ b/include/linux/vm_event_item.h
@@ -32,6 +32,8 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
 		PGREFILL,
 		PGSTEAL_KSWAPD,
 		PGSTEAL_DIRECT,
+		PGDEMOTE_KSWAPD,
+		PGDEMOTE_DIRECT,
 		PGSCAN_KSWAPD,
 		PGSCAN_DIRECT,
 		PGSCAN_DIRECT_THROTTLE,
diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
index 2db8d60..eb5d21c 100644
--- a/include/linux/vmstat.h
+++ b/include/linux/vmstat.h
@@ -29,6 +29,7 @@ struct reclaim_stat {
 	unsigned nr_activate;
 	unsigned nr_ref_keep;
 	unsigned nr_unmap_fail;
+	unsigned nr_demoted;
 };
 
 #ifdef CONFIG_VM_EVENT_COUNTERS
diff --git a/mm/internal.h b/mm/internal.h
index 8c424b5..8ba4853 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -156,6 +156,7 @@ struct scan_control {
 		unsigned int immediate;
 		unsigned int file_taken;
 		unsigned int taken;
+		unsigned int demoted;
 	} nr;
 };
 
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 50cde53..a52c8248 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1511,6 +1511,12 @@ static unsigned long shrink_page_list(struct list_head *page_list,
 
 		nr_reclaimed += nr_succeeded;
 
+		stat->nr_demoted = nr_succeeded;
+		if (current_is_kswapd())
+			__count_vm_events(PGDEMOTE_KSWAPD, stat->nr_demoted);
+		else
+			__count_vm_events(PGDEMOTE_DIRECT, stat->nr_demoted);
+
 		if (err) {
 			if (err == -ENOMEM)
 				set_bit(PGDAT_CONTENDED,
@@ -2019,6 +2025,7 @@ static int current_may_throttle(void)
 	sc->nr.unqueued_dirty += stat.nr_unqueued_dirty;
 	sc->nr.writeback += stat.nr_writeback;
 	sc->nr.immediate += stat.nr_immediate;
+	sc->nr.demoted += stat.nr_demoted;
 	sc->nr.taken += nr_taken;
 	if (file)
 		sc->nr.file_taken += nr_taken;
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 1a431dc..d1e4993 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1192,6 +1192,8 @@ int fragmentation_index(struct zone *zone, unsigned int order)
 	"pgrefill",
 	"pgsteal_kswapd",
 	"pgsteal_direct",
+	"pgdemote_kswapd",
+	"pgdemote_direct",
 	"pgscan_kswapd",
 	"pgscan_direct",
 	"pgscan_direct_throttle",
-- 
1.8.3.1