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From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
To: Michal Hocko <mhocko@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	linux-mm@kvack.org, Johannes Weiner <hannes@cmpxchg.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 0/2] oom, memcg: do not report racy no-eligible OOM
Date: Fri, 11 Jan 2019 23:31:18 +0900	[thread overview]
Message-ID: <d9f7b139-d51b-93ae-b5ad-856fd9f2c168@i-love.sakura.ne.jp> (raw)
In-Reply-To: <20190111133401.GA6997@dhcp22.suse.cz>

On 2019/01/11 22:34, Michal Hocko wrote:
> On Fri 11-01-19 21:40:52, Tetsuo Handa wrote:
> [...]
>> Did you notice that there is no
>>
>>   "Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n"
>>
>> line between
>>
>>   [   71.304703][ T9694] Memory cgroup out of memory: Kill process 9692 (a.out) score 904 or sacrifice child
>>
>> and
>>
>>   [   71.309149][   T54] oom_reaper: reaped process 9750 (a.out), now anon-rss:0kB, file-rss:0kB, shmem-rss:185532kB
>>
>> ? Then, you will find that [ T9694] failed to reach for_each_process(p) loop inside
>> __oom_kill_process() in the first round of out_of_memory() call because
>> find_lock_task_mm() == NULL at __oom_kill_process() because Ctrl-C made that victim
>> complete exit_mm() before find_lock_task_mm() is called.
> 
> OK, so we haven't killed anything because the victim has exited by the
> time we wanted to do so. We still have other tasks sharing that mm
> pending and not killed because nothing has killed them yet, right?

The OOM killer invoked by [ T9694] called printk() but didn't kill anything.
Instead, SIGINT from Ctrl-C killed all thread groups sharing current->mm.

> 
> How come the oom reaper could act on this oom event at all then?
> 
> What am I missing?
> 

The OOM killer invoked by [ T9750] did not call printk() but hit
task_will_free_mem(current) in out_of_memory() and invoked the OOM reaper,
without calling mark_oom_victim() on all thread groups sharing current->mm.
Did you notice that I wrote that

  Since mm-oom-marks-all-killed-tasks-as-oom-victims.patch does not call mark_oom_victim()
  when task_will_free_mem() == true,

? :-(


  reply	other threads:[~2019-01-11 15:02 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-07 14:38 [PATCH 0/2] oom, memcg: do not report racy no-eligible OOM Michal Hocko
2019-01-07 14:38 ` Michal Hocko
2019-01-07 14:38 ` [PATCH 1/2] mm, oom: marks all killed tasks as oom victims Michal Hocko
2019-01-07 14:38   ` Michal Hocko
2019-01-07 20:58   ` Tetsuo Handa
2019-01-08  8:11     ` Michal Hocko
2019-01-07 14:38 ` [PATCH 2/2] memcg: do not report racy no-eligible OOM tasks Michal Hocko
2019-01-07 14:38   ` Michal Hocko
2019-01-07 20:59   ` Tetsuo Handa
2019-01-08  8:14     ` Michal Hocko
2019-01-08 10:39       ` Tetsuo Handa
2019-01-08 11:46         ` Michal Hocko
2019-01-08  8:35   ` kbuild test robot
2019-01-08  9:39     ` Michal Hocko
2019-01-11  0:23       ` [kbuild-all] " Rong Chen
2019-01-08 14:21 ` [PATCH 3/2] memcg: Facilitate termination of memcg OOM victims Tetsuo Handa
2019-01-08 14:38   ` Michal Hocko
2019-01-09 11:03 ` [PATCH 0/2] oom, memcg: do not report racy no-eligible OOM Michal Hocko
2019-01-09 11:34   ` Tetsuo Handa
2019-01-09 12:02     ` Michal Hocko
2019-01-10 23:59       ` Tetsuo Handa
2019-01-11 10:25         ` Tetsuo Handa
2019-01-11 11:33           ` Michal Hocko
2019-01-11 12:40             ` Tetsuo Handa
2019-01-11 13:34               ` Michal Hocko
2019-01-11 14:31                 ` Tetsuo Handa [this message]
2019-01-11 15:07                   ` Michal Hocko
2019-01-11 15:37                     ` Tetsuo Handa
2019-01-11 16:45                       ` Michal Hocko
2019-01-12 10:52                         ` Tetsuo Handa
2019-01-13 17:36                           ` Michal Hocko

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