[PATCH v2 4/5] mm: use node_page_state_snapshot to avoid deviation

[Kemi Wang]

To avoid deviation, this patch uses node_page_state_snapshot instead of
node_page_state for node page stats query.
e.g. cat /proc/zoneinfo
     cat /sys/devices/system/node/node*/vmstat
     cat /sys/devices/system/node/node*/numastat

As it is a slow path and would not be read frequently, I would worry about
it.

Signed-off-by: Kemi Wang <kemi.wang@xxxxxxxxx>
---
 drivers/base/node.c | 17 ++++++++++-------
 mm/vmstat.c         |  2 +-
 2 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/drivers/base/node.c b/drivers/base/node.c
index a045ea1..cf303f8 100644
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -169,12 +169,15 @@ static ssize_t node_read_numastat(struct device *dev,
 		       "interleave_hit %lu\n"
 		       "local_node %lu\n"
 		       "other_node %lu\n",
-		       node_page_state(NODE_DATA(dev->id), NUMA_HIT),
-		       node_page_state(NODE_DATA(dev->id), NUMA_MISS),
-		       node_page_state(NODE_DATA(dev->id), NUMA_FOREIGN),
-		       node_page_state(NODE_DATA(dev->id), NUMA_INTERLEAVE_HIT),
-		       node_page_state(NODE_DATA(dev->id), NUMA_LOCAL),
-		       node_page_state(NODE_DATA(dev->id), NUMA_OTHER));
+		       node_page_state_snapshot(NODE_DATA(dev->id), NUMA_HIT),
+		       node_page_state_snapshot(NODE_DATA(dev->id), NUMA_MISS),
+		       node_page_state_snapshot(NODE_DATA(dev->id),
+			       NUMA_FOREIGN),
+		       node_page_state_snapshot(NODE_DATA(dev->id),
+			       NUMA_INTERLEAVE_HIT),
+		       node_page_state_snapshot(NODE_DATA(dev->id), NUMA_LOCAL),
+		       node_page_state_snapshot(NODE_DATA(dev->id),
+			       NUMA_OTHER));
 }
 
 static DEVICE_ATTR(numastat, S_IRUGO, node_read_numastat, NULL);
@@ -194,7 +197,7 @@ static ssize_t node_read_vmstat(struct device *dev,
 	for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++)
 		n += sprintf(buf+n, "%s %lu\n",
 			     vmstat_text[i + NR_VM_ZONE_STAT_ITEMS],
-			     node_page_state(pgdat, i));
+			     node_page_state_snapshot(pgdat, i));
 
 	return n;
 }
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 64e08ae..d65f28d 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1466,7 +1466,7 @@ static void zoneinfo_show_print(struct seq_file *m, pg_data_t *pgdat,
 		for (i = 0; i < NR_VM_NODE_STAT_ITEMS; i++) {
 			seq_printf(m, "\n      %-12s %lu",
 				vmstat_text[i + NR_VM_ZONE_STAT_ITEMS],
-				node_page_state(pgdat, i));
+				node_page_state_snapshot(pgdat, i));
 		}
 	}
 	seq_printf(m,
-- 
2.7.4