Re: [RFC][PATCH 5/5] memcg: drain per cpu stock

["KAMEZAWA Hiroyuki" <kamezawa.hiroyu@jp.fujitsu.com>]

Balbir Singh さんは書きました：
> * KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2009-08-28
> 13:28:09]:
>
>>
>> Add function for dropping per-cpu stock of charges.
>> This is called when
>> 	- cpu is unplugged.
>> 	- force_empty
>> 	- recalim seems to be not easy.
>>
>> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
>
> The complexity of this patch and additional code make percpu_counter
> more attractive. Why not work on percpu_counter if that is not as good
> as we expect it to be and in turn help other exploiters as well.

- percpu counter is slow.
- percpu counter is "counter". we use res_counter not as counter but as
  accounting for "limit". This "borrow" charges is core of this patch.
- Adding "flush" ops for percpu counter will be much more mess.
- This implementation handles mem->res and mem->memsw at the same time.
  This reduces much overhead.

Thanks,
-Kame