[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.w...@intel.com>
---
 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