[RFC 6/8] add PGVOLATILE vmstat count

[Minchan Kim <minchan@kernel.org>]

This patch add pgvolatile vmstat so admin can see how many of volatile
pages are discarded by VM until now.

Signed-off-by: Minchan Kim <minchan@kernel.org>
---
 include/linux/vm_event_item.h |    3 +++
 mm/mvolatile.c                |    1 +
 mm/vmstat.c                   |    3 +++
 3 files changed, 7 insertions(+)

diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h
index 3d31145..721d096 100644
--- a/include/linux/vm_event_item.h
+++ b/include/linux/vm_event_item.h
@@ -25,6 +25,9 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
 		FOR_ALL_ZONES(PGALLOC),
 		PGFREE, PGACTIVATE, PGDEACTIVATE,
 		PGFAULT, PGMAJFAULT,
+#ifdef CONFIG_VOLATILE_PAGE
+		PGVOLATILE,
+#endif
 		FOR_ALL_ZONES(PGREFILL),
 		FOR_ALL_ZONES(PGSTEAL_KSWAPD),
 		FOR_ALL_ZONES(PGSTEAL_DIRECT),
diff --git a/mm/mvolatile.c b/mm/mvolatile.c
index 6bc9f7e..c66c3bc 100644
--- a/mm/mvolatile.c
+++ b/mm/mvolatile.c
@@ -201,6 +201,7 @@ int discard_volatile_page(struct page *page, enum ttu_flags ttu_flags)
 	if (try_to_volatile_page(page, ttu_flags)) {
 		if (page_freeze_refs(page, 1)) {
 			unlock_page(page);
+			count_vm_event(PGVOLATILE);
 			return 1;
 		}
 	}
diff --git a/mm/vmstat.c b/mm/vmstat.c
index c737057..3d08e1a 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -753,6 +753,9 @@ const char * const vmstat_text[] = {
 	"pgfault",
 	"pgmajfault",
 
+#ifdef CONFIG_VOLATILE_PAGE
+	"pgvolatile",
+#endif
 	TEXTS_FOR_ZONES("pgrefill")
 	TEXTS_FOR_ZONES("pgsteal_kswapd")
 	TEXTS_FOR_ZONES("pgsteal_direct")
-- 
1.7.9.5

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