[Devel] Re: [RFC 5/7] use percpu_counters for res_counter usage

[KAMEZAWA Hiroyuki]

(2012/03/30 22:53), Glauber Costa wrote:

> On 03/30/2012 11:58 AM, KAMEZAWA Hiroyuki wrote:
>> ==
>>
>> Now, we do consume 'reserved' usage, we can avoid css_get(), an heavy atomic
>> ops. You may need to move this code as
>>
>> 	rcu_read_lock()
>> 	....
>> 	res_counter_charge()
>> 	if (failure) {
>> 		css_tryget()
>> 		rcu_read_unlock()
>> 	} else {
>> 		rcu_read_unlock()
>> 		return success;
>> 	}
>>
>> to compare performance. This css_get() affects performance very very much.
> 
> thanks for the tip.
> 
> But one thing:
> 
> To be sure: it effectively mean that we are drawing from a dead memcg
> (because we pre-allocated, right?

Cached stock is consumed by the current task. It blocks removal of memcg.
It's not dead.

Thanks,
-Kame