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Subject[PATCH 6/12] memcg optimize percpu stat
Some obvious optimization to memcg.

I found mem_cgroup_charge_statistics() is a little big (in object) and
does unnecessary address calclation.
This patch is for optimization to reduce the size of this function.

And res_counter_charge() is 'likely' to success.

Changelog v3->v4:
- merged with an other leaf patch.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

mm/memcontrol.c | 18 ++++++++++--------
1 file changed, 10 insertions(+), 8 deletions(-)
Index: mmotm-2.6.27-rc7+/mm/memcontrol.c
===================================================================
--- mmotm-2.6.27-rc7+.orig/mm/memcontrol.c
+++ mmotm-2.6.27-rc7+/mm/memcontrol.c
@@ -66,11 +66,10 @@ struct mem_cgroup_stat {
/*
* For accounting under irq disable, no need for increment preempt count.
*/
-static void __mem_cgroup_stat_add_safe(struct mem_cgroup_stat *stat,
+static inline void __mem_cgroup_stat_add_safe(struct mem_cgroup_stat_cpu *stat,
enum mem_cgroup_stat_index idx, int val)
{
- int cpu = smp_processor_id();
- stat->cpustat[cpu].count[idx] += val;
+ stat->count[idx] += val;
}

static s64 mem_cgroup_read_stat(struct mem_cgroup_stat *stat,
@@ -237,18 +236,21 @@ static void mem_cgroup_charge_statistics
{
int val = (charge)? 1 : -1;
struct mem_cgroup_stat *stat = &mem->stat;
+ struct mem_cgroup_stat_cpu *cpustat;

VM_BUG_ON(!irqs_disabled());
+
+ cpustat = &stat->cpustat[smp_processor_id()];
if (PageCgroupCache(pc))
- __mem_cgroup_stat_add_safe(stat, MEM_CGROUP_STAT_CACHE, val);
+ __mem_cgroup_stat_add_safe(cpustat, MEM_CGROUP_STAT_CACHE, val);
else
- __mem_cgroup_stat_add_safe(stat, MEM_CGROUP_STAT_RSS, val);
+ __mem_cgroup_stat_add_safe(cpustat, MEM_CGROUP_STAT_RSS, val);

if (charge)
- __mem_cgroup_stat_add_safe(stat,
+ __mem_cgroup_stat_add_safe(cpustat,
MEM_CGROUP_STAT_PGPGIN_COUNT, 1);
else
- __mem_cgroup_stat_add_safe(stat,
+ __mem_cgroup_stat_add_safe(cpustat,
MEM_CGROUP_STAT_PGPGOUT_COUNT, 1);
}

@@ -609,7 +611,7 @@ static int mem_cgroup_charge_common(stru
css_get(&memcg->css);
}

- while (res_counter_charge(&mem->res, PAGE_SIZE)) {
+ while (unlikely(res_counter_charge(&mem->res, PAGE_SIZE))) {
if (!(gfp_mask & __GFP_WAIT))
goto out;



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