[cpuops inc_return V1 4/9] vmstat: Use this_cpu_inc_return for vm statistics

[Christoph Lameter]

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@xxxxxxxxxx>
Signed-off-by: Christoph Lameter <cl@xxxxxxxxx>

---
 mm/vmstat.c |    8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

Index: linux-2.6/mm/vmstat.c
===================================================================
--- linux-2.6.orig/mm/vmstat.c	2010-11-29 10:36:16.000000000 -0600
+++ linux-2.6/mm/vmstat.c	2010-11-29 10:38:50.000000000 -0600
@@ -227,9 +227,7 @@ void __inc_zone_state(struct zone *zone,
 	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,
 	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;

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