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Subject[thisops uV2 06/10] 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

Signed-off-by: Christoph Lameter <cl@linux.com>

---
mm/vmstat.c | 20 ++++++++------------
1 file changed, 8 insertions(+), 12 deletions(-)
Index: linux-2.6/mm/vmstat.c
===================================================================
--- linux-2.6.orig/mm/vmstat.c 2010-11-26 10:35:45.000000000 -0600
+++ linux-2.6/mm/vmstat.c 2010-11-26 10:45:49.000000000 -0600
@@ -167,8 +167,8 @@ static void refresh_zone_stat_thresholds
void __mod_zone_page_state(struct zone *zone, enum zone_stat_item item,
int delta)
{
- struct per_cpu_pageset * __percpu pcp = zone->pageset;
- s8 * __percpu p = pcp->vm_stat_diff + item;
+ struct per_cpu_pageset __percpu *pcp = zone->pageset;
+ s8 __percpu *p = pcp->vm_stat_diff + item;
long x;
long t;

@@ -223,13 +223,11 @@ EXPORT_SYMBOL(mod_zone_page_state);
*/
void __inc_zone_state(struct zone *zone, enum zone_stat_item item)
{
- struct per_cpu_pageset * __percpu pcp = zone->pageset;
- s8 * __percpu p = pcp->vm_stat_diff + item;
+ struct per_cpu_pageset __percpu *pcp = zone->pageset;
+ 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;
@@ -247,13 +245,11 @@ EXPORT_SYMBOL(__inc_zone_page_state);

void __dec_zone_state(struct zone *zone, enum zone_stat_item item)
{
- struct per_cpu_pageset * __percpu pcp = zone->pageset;
- s8 * __percpu p = pcp->vm_stat_diff + item;
+ struct per_cpu_pageset __percpu *pcp = zone->pageset;
+ 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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