Re: [PATCH V3 7/8] memcg: disable memcg page stat accounting code when not in use

[Sha Zhengju <handai.szj@gmail.com>]

On Fri, Dec 28, 2012 at 9:45 AM, Kamezawa Hiroyuki
<kamezawa.hiroyu@jp.fujitsu.com> wrote:
> (2012/12/26 2:27), Sha Zhengju wrote:
>> From: Sha Zhengju <handai.szj@taobao.com>
>>
>> It's inspired by a similar optimization from Glauber Costa
>> (memcg: make it suck faster; https://lkml.org/lkml/2012/9/25/154).
>> Here we use jump label to patch the memcg page stat accounting code
>> in or out when not used. when the first non-root memcg comes to
>> life the code is patching in otherwise it is out.
>>
>> Signed-off-by: Sha Zhengju <handai.szj@taobao.com>
>> ---
>>   include/linux/memcontrol.h |    9 +++++++++
>>   mm/memcontrol.c            |    8 ++++++++
>>   2 files changed, 17 insertions(+)
>>
>> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
>> index 1d22b81..3c4430c 100644
>> --- a/include/linux/memcontrol.h
>> +++ b/include/linux/memcontrol.h
>> @@ -56,6 +56,9 @@ struct mem_cgroup_reclaim_cookie {
>>   };
>>
>>   #ifdef CONFIG_MEMCG
>> +
>> +extern struct static_key memcg_in_use_key;
>> +
>>   /*
>>    * All "charge" functions with gfp_mask should use GFP_KERNEL or
>>    * (gfp_mask & GFP_RECLAIM_MASK). In current implementatin, memcg doesn't
>> @@ -158,6 +161,9 @@ extern atomic_t memcg_moving;
>>   static inline void mem_cgroup_begin_update_page_stat(struct page *page,
>>                                       bool *locked, unsigned long *flags)
>>   {
>> +     if (!static_key_false(&memcg_in_use_key))
>> +             return;
>> +
>>       if (mem_cgroup_disabled())
>>               return;
>>       rcu_read_lock();
>> @@ -171,6 +177,9 @@ void __mem_cgroup_end_update_page_stat(struct page *page,
>>   static inline void mem_cgroup_end_update_page_stat(struct page *page,
>>                                       bool *locked, unsigned long *flags)
>>   {
>> +     if (!static_key_false(&memcg_in_use_key))
>> +             return;
>> +
>>       if (mem_cgroup_disabled())
>>               return;
>>       if (*locked)
>> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
>> index 0cb5187..a2f73d7 100644
>> --- a/mm/memcontrol.c
>> +++ b/mm/memcontrol.c
>> @@ -531,6 +531,8 @@ enum res_type {
>>   #define MEM_CGROUP_RECLAIM_SHRINK_BIT       0x1
>>   #define MEM_CGROUP_RECLAIM_SHRINK   (1 << MEM_CGROUP_RECLAIM_SHRINK_BIT)
>>
>> +struct static_key memcg_in_use_key;
>> +
>>   static void mem_cgroup_get(struct mem_cgroup *memcg);
>>   static void mem_cgroup_put(struct mem_cgroup *memcg);
>>
>> @@ -2226,6 +2228,9 @@ void mem_cgroup_update_page_stat(struct page *page,
>>       struct page_cgroup *pc = lookup_page_cgroup(page);
>>       unsigned long uninitialized_var(flags);
>>
>> +     if (!static_key_false(&memcg_in_use_key))
>> +             return;
>> +
>>       if (mem_cgroup_disabled())
>>               return;
>>
>> @@ -6340,6 +6345,8 @@ mem_cgroup_css_alloc(struct cgroup *cont)
>>               parent = mem_cgroup_from_cont(cont->parent);
>>               memcg->use_hierarchy = parent->use_hierarchy;
>>               memcg->oom_kill_disable = parent->oom_kill_disable;
>> +
>> +             static_key_slow_inc(&memcg_in_use_key);
>>       }
>>
>>       if (parent && parent->use_hierarchy) {
>> @@ -6407,6 +6414,7 @@ static void mem_cgroup_css_free(struct cgroup *cont)
>>       kmem_cgroup_destroy(memcg);
>>
>>       memcg_dangling_add(memcg);
>> +     static_key_slow_dec(&memcg_in_use_key);
>
> Hmm. I think this part should be folded into disarm_static_keys().
>

Yeah, now I think there is more suitable.


Thanks,
Sha

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