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

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

On 03/30/2012 11:58 AM, KAMEZAWA Hiroyuki wrote:

quoted

==

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