Commit 63803222 authored by Kemi Wang's avatar Kemi Wang Committed by Linus Torvalds
Browse files

mm: consider the number in local CPUs when reading NUMA stats

To avoid deviation, the per cpu number of NUMA stats in
vm_numa_stat_diff[] is included when a user *reads* the NUMA stats.

Since NUMA stats does not be read by users frequently, and kernel does not
need it to make a decision, it will not be a problem to make the readers
more expensive.


Signed-off-by: default avatarKemi Wang <>
Reported-by: default avatarJesper Dangaard Brouer <>
Acked-by: default avatarMel Gorman <>
Cc: Aaron Lu <>
Cc: Andi Kleen <>
Cc: Christopher Lameter <>
Cc: Dave Hansen <>
Cc: Johannes Weiner <>
Cc: Michal Hocko <>
Cc: Tim Chen <>
Cc: Ying Huang <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 1d90ca89
......@@ -125,10 +125,14 @@ static inline unsigned long global_numa_state(enum numa_stat_item item)
return x;
static inline unsigned long zone_numa_state(struct zone *zone,
static inline unsigned long zone_numa_state_snapshot(struct zone *zone,
enum numa_stat_item item)
long x = atomic_long_read(&zone->vm_numa_stat[item]);
int cpu;
x += per_cpu_ptr(zone->pageset, cpu)->vm_numa_stat_diff[item];
return x;
......@@ -897,6 +897,10 @@ unsigned long sum_zone_node_page_state(int node,
return count;
* Determine the per node value of a numa stat item. To avoid deviation,
* the per cpu stat number in vm_numa_stat_diff[] is also included.
unsigned long sum_zone_numa_state(int node,
enum numa_stat_item item)
......@@ -905,7 +909,7 @@ unsigned long sum_zone_numa_state(int node,
unsigned long count = 0;
for (i = 0; i < MAX_NR_ZONES; i++)
count += zone_numa_state(zones + i, item);
count += zone_numa_state_snapshot(zones + i, item);
return count;
......@@ -1536,7 +1540,7 @@ static void zoneinfo_show_print(struct seq_file *m, pg_data_t *pgdat,
for (i = 0; i < NR_VM_NUMA_STAT_ITEMS; i++)
seq_printf(m, "\n %-12s %lu",
vmstat_text[i + NR_VM_ZONE_STAT_ITEMS],
zone_numa_state(zone, i));
zone_numa_state_snapshot(zone, i));
seq_printf(m, "\n pagesets");
......@@ -1792,6 +1796,7 @@ static bool need_update(int cpu)
BUILD_BUG_ON(sizeof(p->vm_numa_stat_diff[0]) != 2);
* The fast way of checking if there are any vmstat diffs.
* This works because the diffs are byte sized items.
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