[PATCH 06/10] mm/vmscan: add page demotion counter

[Dave Hansen]

From: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx>

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

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

[ daveh:
   - __count_vm_events() a bit, and made them look at the THP
     size directly rather than getting data from migrate_pages()
]

Signed-off-by: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx>
Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Reviewed-by: Yang Shi <shy828301@xxxxxxxxx>
Cc: Wei Xu <weixugc@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Huang Ying <ying.huang@xxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: osalvador <osalvador@xxxxxxx>

--

Changes since 202010:
 * remove unused scan-control 'demoted' field
---

 b/include/linux/vm_event_item.h |    2 ++
 b/mm/vmscan.c                   |    5 +++++
 b/mm/vmstat.c                   |    2 ++
 3 files changed, 9 insertions(+)

diff -puN include/linux/vm_event_item.h~mm-vmscan-add-page-demotion-counter include/linux/vm_event_item.h
--- a/include/linux/vm_event_item.h~mm-vmscan-add-page-demotion-counter	2021-03-31 15:17:17.079000248 -0700
+++ b/include/linux/vm_event_item.h	2021-03-31 15:17:17.101000248 -0700
@@ -33,6 +33,8 @@ enum vm_event_item { PGPGIN, PGPGOUT, PS
 		PGREUSE,
 		PGSTEAL_KSWAPD,
 		PGSTEAL_DIRECT,
+		PGDEMOTE_KSWAPD,
+		PGDEMOTE_DIRECT,
 		PGSCAN_KSWAPD,
 		PGSCAN_DIRECT,
 		PGSCAN_DIRECT_THROTTLE,
diff -puN mm/vmscan.c~mm-vmscan-add-page-demotion-counter mm/vmscan.c
--- a/mm/vmscan.c~mm-vmscan-add-page-demotion-counter	2021-03-31 15:17:17.081000248 -0700
+++ b/mm/vmscan.c	2021-03-31 15:17:17.109000248 -0700
@@ -1120,6 +1120,11 @@ static unsigned int demote_page_list(str
 			    target_nid, MIGRATE_ASYNC, MR_DEMOTION,
 			    &nr_succeeded);
 
+	if (current_is_kswapd())
+		__count_vm_events(PGDEMOTE_KSWAPD, nr_succeeded);
+	else
+		__count_vm_events(PGDEMOTE_DIRECT, nr_succeeded);
+
 	return nr_succeeded;
 }
 
diff -puN mm/vmstat.c~mm-vmscan-add-page-demotion-counter mm/vmstat.c
--- a/mm/vmstat.c~mm-vmscan-add-page-demotion-counter	2021-03-31 15:17:17.092000248 -0700
+++ b/mm/vmstat.c	2021-03-31 15:17:17.116000248 -0700
@@ -1259,6 +1259,8 @@ const char * const vmstat_text[] = {
 	"pgreuse",
 	"pgsteal_kswapd",
 	"pgsteal_direct",
+	"pgdemote_kswapd",
+	"pgdemote_direct",
 	"pgscan_kswapd",
 	"pgscan_direct",
 	"pgscan_direct_throttle",
_