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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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