linux-kernel - Re: [PATCH 2/2] memcg: change memcg_oom

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Message-ID: <CAKTCnzkiRW3aLwnCYyb9XPfTZWipqcA5Jd7d27rZpecqn3wFuQ@mail.gmail.com>
Date:	Wed, 20 Jul 2011 12:04:17 +0530
From:	Balbir Singh <bsingharora@...il.com>
To:	Michal Hocko <mhocko@...e.cz>
Cc:	linux-mm@...ck.org,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] memcg: change memcg_oom_mutex to spinlock

On Thu, Jul 14, 2011 at 8:59 PM, Michal Hocko <mhocko@...e.cz> wrote:
> memcg_oom_mutex is used to protect memcg OOM path and eventfd interface
> for oom_control. None of the critical sections which it protects sleep
> (eventfd_signal works from atomic context and the rest are simple linked
> list resp. oom_lock atomic operations).
> Mutex is also too heavy weight for those code paths because it triggers
> a lot of scheduling. It also makes makes convoying effects more visible
> when we have a big number of oom killing because we take the lock
> mutliple times during mem_cgroup_handle_oom so we have multiple places
> where many processes can sleep.
>
> Signed-off-by: Michal Hocko <mhocko@...e.cz>

Quick question: How long do we expect this lock to be taken? What
happens under oom? Any tests? Numbers?

Balbir Singh
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