vmstat: Use this_cpu_inc_return for vm statistics

this_cpu_inc_return() saves us a memory access there. Code
size does not change.

V1->V2:
	- Fixed the location of the __per_cpu pointer attributes
	- Sparse checked
V2->V3:
	- Move fixes to __percpu attribute usage to earlier patch

Reviewed-by: Pekka Enberg <penberg@kernel.org>
Acked-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

1 files changed, 2 insertions, 6 deletions

diff --git a/mm/vmstat.c b/mm/vmstat.c
index 3ad909d9600f..f9a7bc89fd10 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -227,9 +227,7 @@ void __inc_zone_state(struct zone *zone, enum zone_stat_item item)
         s8 __percpu *p = pcp->vm_stat_diff + item;
         s8 v, t;
 
-        __this_cpu_inc(*p);
-
-        v = __this_cpu_read(*p);
+        v = __this_cpu_inc_return(*p);
         t = __this_cpu_read(pcp->stat_threshold);
         if (unlikely(v > t)) {
                 s8 overstep = t >> 1;
@@ -251,9 +249,7 @@ void __dec_zone_state(struct zone *zone, enum zone_stat_item item)
         s8 __percpu *p = pcp->vm_stat_diff + item;
         s8 v, t;
 
-        __this_cpu_dec(*p);
-
-        v = __this_cpu_read(*p);
+        v = __this_cpu_dec_return(*p);
         t = __this_cpu_read(pcp->stat_threshold);
         if (unlikely(v < - t)) {
                 s8 overstep = t >> 1;