[PATCH 14/14] vrange: Add vmstat counter about purged page

[John Stultz]

From: Minchan Kim <minchan@xxxxxxxxxx>

This patch adds the number of purged page in vmstat so admin can see
how many of volatile pages are discarded by VM until now.

Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Android Kernel Team <kernel-team@xxxxxxxxxxx>
Cc: Robert Love <rlove@xxxxxxxxxx>
Cc: Mel Gorman <mel@xxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Dmitry Adamushko <dmitry.adamushko@xxxxxxxxx>
Cc: Dave Chinner <david@xxxxxxxxxxxxx>
Cc: Neil Brown <neilb@xxxxxxx>
Cc: Andrea Righi <andrea@xxxxxxxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
Cc: Mike Hommey <mh@xxxxxxxxxxxx>
Cc: Taras Glek <tglek@xxxxxxxxxxx>
Cc: Dhaval Giani <dhaval.giani@xxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxx>
Cc: Michel Lespinasse <walken@xxxxxxxxxx>
Cc: Rob Clark <robdclark@xxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: linux-mm@xxxxxxxxx <linux-mm@xxxxxxxxx>
Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
Signed-off-by: John Stultz <john.stultz@xxxxxxxxxx>
---
 include/linux/vm_event_item.h |  2 ++
 mm/vmstat.c                   |  2 ++
 mm/vrange.c                   | 10 ++++++++++
 3 files changed, 14 insertions(+)

diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h
index bd6cf61..c4aea92 100644
--- a/include/linux/vm_event_item.h
+++ b/include/linux/vm_event_item.h
@@ -25,6 +25,8 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
 		FOR_ALL_ZONES(PGALLOC),
 		PGFREE, PGACTIVATE, PGDEACTIVATE,
 		PGFAULT, PGMAJFAULT,
+		PGDISCARD_DIRECT,
+		PGDISCARD_KSWAPD,
 		FOR_ALL_ZONES(PGREFILL),
 		FOR_ALL_ZONES(PGSTEAL_KSWAPD),
 		FOR_ALL_ZONES(PGSTEAL_DIRECT),
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 20c2ef4..4f35f46 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -756,6 +756,8 @@ const char * const vmstat_text[] = {
 
 	"pgfault",
 	"pgmajfault",
+	"pgdiscard_direct",
+	"pgdiscard_kswapd",
 
 	TEXTS_FOR_ZONES("pgrefill")
 	TEXTS_FOR_ZONES("pgsteal_kswapd")
diff --git a/mm/vrange.c b/mm/vrange.c
index c30e3dd..8931fab 100644
--- a/mm/vrange.c
+++ b/mm/vrange.c
@@ -894,6 +894,10 @@ int discard_vpage(struct page *page)
 
 		if (page_freeze_refs(page, 1)) {
 			unlock_page(page);
+			if (current_is_kswapd())
+				count_vm_event(PGDISCARD_KSWAPD);
+			else
+				count_vm_event(PGDISCARD_DIRECT);
 			return 0;
 		}
 	}
@@ -1144,6 +1148,12 @@ static int discard_vrange(struct vrange *vrange)
 		ret = __discard_vrange_file(mapping, vrange, &nr_discard);
 	}
 
+	if (!ret) {
+		if (current_is_kswapd())
+			count_vm_events(PGDISCARD_KSWAPD, nr_discard);
+		else
+			count_vm_events(PGDISCARD_DIRECT, nr_discard);
+	}
 out:
 	__vroot_put(vroot);
 	return nr_discard;
-- 
1.8.1.2

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