mm, vmstat: suppress pcp stats for unpopulated zones in zoneinfo

After "mm, vmstat: print non-populated zones in zoneinfo",
/proc/zoneinfo will show unpopulated zones.

The per-cpu pageset statistics are not relevant for unpopulated zones
and can be potentially lengthy, so supress them when they are not
interesting.

Also moves lowmem reserve protection information above pcp stats since
it is relevant for all zones per vm.lowmem_reserve_ratio.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: David Rientjes <[email protected]>
Cc: Anshuman Khandual <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Johannes Weiner <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 13 insertions, 7 deletions

diff --git a/mm/vmstat.c b/mm/vmstat.c
index a828b17ced1a..f5fa1bd1eb16 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1393,18 +1393,24 @@ static void zoneinfo_show_print(struct seq_file *m, pg_data_t *pgdat,
 		   zone->present_pages,
 		   zone->managed_pages);
 
-	for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++)
-		seq_printf(m, "\n      %-12s %lu", vmstat_text[i],
-				zone_page_state(zone, i));
-
 	seq_printf(m,
 		   "\n        protection: (%ld",
 		   zone->lowmem_reserve[0]);
 	for (i = 1; i < ARRAY_SIZE(zone->lowmem_reserve); i++)
 		seq_printf(m, ", %ld", zone->lowmem_reserve[i]);
-	seq_printf(m,
-		   ")"
-		   "\n  pagesets");
+	seq_putc(m, ')');
+
+	/* If unpopulated, no other information is useful */
+	if (!populated_zone(zone)) {
+		seq_putc(m, '\n');
+		return;
+	}
+
+	for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++)
+		seq_printf(m, "\n      %-12s %lu", vmstat_text[i],
+				zone_page_state(zone, i));
+
+	seq_printf(m, "\n  pagesets");
 	for_each_online_cpu(i) {
 		struct per_cpu_pageset *pageset;