From: Yang Shi <redacted>

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 <redacted>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Huang Ying <redacted>
Cc: Dan Williams <redacted>
Cc: David Hildenbrand <redacted>
Cc: osalvador <osalvador@suse.de>

--

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	2021-01-25 16:23:15.821866693 -0800
+++ b/include/linux/vm_event_item.h	2021-01-25 16:23:15.831866693 -0800

@@ -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	2021-01-25 16:23:15.823866693 -0800
+++ b/mm/vmscan.c	2021-01-25 16:23:15.835866693 -0800

@@ -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	2021-01-25 16:23:15.825866693 -0800
+++ b/mm/vmstat.c	2021-01-25 16:23:15.838866693 -0800

@@ -1244,6 +1244,8 @@ const char * const vmstat_text[] = {
 	"pgreuse",
 	"pgsteal_kswapd",
 	"pgsteal_direct",
+	"pgdemote_kswapd",
+	"pgdemote_direct",
 	"pgscan_kswapd",
 	"pgscan_direct",
 	"pgscan_direct_throttle",

_