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authorChristoph Lameter <cl@linux.com>2010-12-06 11:16:20 -0600
committerTejun Heo <tj@kernel.org>2010-12-17 15:07:18 +0100
commit12938a9220a38d555e38dc9b40021e664b99a1f1 (patch)
tree978c0199dcd22faf92250fcfd5bfa2aac1100baa /mm/vmstat.c
parent819a72af8d6653daa48334f24ce0a935ccdd33c7 (diff)
downloadlinux-12938a9220a38d555e38dc9b40021e664b99a1f1.tar.gz
vmstat: Optimize zone counter modifications through the use of this cpu operations
this cpu operations can be used to slightly optimize the function. The changes will avoid some address calculations and replace them with the use of the percpu segment register. If one would have this_cpu_inc_return and this_cpu_dec_return then it would be possible to optimize inc_zone_page_state and dec_zone_page_state even more. V1->V2: - Fix __dec_zone_state overflow handling - Use s8 variables for temporary storage. V2->V3: - Put __percpu annotations in correct places. 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>
Diffstat (limited to 'mm/vmstat.c')
-rw-r--r--mm/vmstat.c48
1 files changed, 28 insertions, 20 deletions
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 8f62f17ee1c..3ad909d9600 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -167,18 +167,20 @@ static void refresh_zone_stat_thresholds(void)
void __mod_zone_page_state(struct zone *zone, enum zone_stat_item item,
int delta)
{
- struct per_cpu_pageset *pcp = this_cpu_ptr(zone->pageset);
-
- s8 *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;
+
+ x = delta + __this_cpu_read(*p);
- x = delta + *p;
+ t = __this_cpu_read(pcp->stat_threshold);
- if (unlikely(x > pcp->stat_threshold || x < -pcp->stat_threshold)) {
+ if (unlikely(x > t || x < -t)) {
zone_page_state_add(x, zone, item);
x = 0;
}
- *p = x;
+ __this_cpu_write(*p, x);
}
EXPORT_SYMBOL(__mod_zone_page_state);
@@ -221,16 +223,19 @@ EXPORT_SYMBOL(mod_zone_page_state);
*/
void __inc_zone_state(struct zone *zone, enum zone_stat_item item)
{
- struct per_cpu_pageset *pcp = this_cpu_ptr(zone->pageset);
- s8 *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;
- (*p)++;
+ __this_cpu_inc(*p);
- if (unlikely(*p > pcp->stat_threshold)) {
- int overstep = pcp->stat_threshold / 2;
+ v = __this_cpu_read(*p);
+ t = __this_cpu_read(pcp->stat_threshold);
+ if (unlikely(v > t)) {
+ s8 overstep = t >> 1;
- zone_page_state_add(*p + overstep, zone, item);
- *p = -overstep;
+ zone_page_state_add(v + overstep, zone, item);
+ __this_cpu_write(*p, -overstep);
}
}
@@ -242,16 +247,19 @@ EXPORT_SYMBOL(__inc_zone_page_state);
void __dec_zone_state(struct zone *zone, enum zone_stat_item item)
{
- struct per_cpu_pageset *pcp = this_cpu_ptr(zone->pageset);
- s8 *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;
- (*p)--;
+ __this_cpu_dec(*p);
- if (unlikely(*p < - pcp->stat_threshold)) {
- int overstep = pcp->stat_threshold / 2;
+ v = __this_cpu_read(*p);
+ t = __this_cpu_read(pcp->stat_threshold);
+ if (unlikely(v < - t)) {
+ s8 overstep = t >> 1;
- zone_page_state_add(*p - overstep, zone, item);
- *p = overstep;
+ zone_page_state_add(v - overstep, zone, item);
+ __this_cpu_write(*p, overstep);
}
}