From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
To: mhocko@kernel.org, linux-mm@kvack.org
Cc: rientjes@google.com, oleg@redhat.com, vdavydov@parallels.com,
akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
mhocko@suse.com
Subject: Re: [PATCH 08/10] mm, oom: task_will_free_mem should skip oom_reaped tasks
Date: Fri, 17 Jun 2016 20:35:38 +0900 [thread overview]
Message-ID: <201606172035.BCG92033.HtSOFOOMVLJFFQ@I-love.SAKURA.ne.jp> (raw)
In-Reply-To: <1465473137-22531-9-git-send-email-mhocko@kernel.org>
Michal Hocko wrote:
> From: Michal Hocko <mhocko@suse.com>
>
> 0-day robot has encountered the following:
> [ 82.694232] Out of memory: Kill process 3914 (trinity-c0) score 167 or sacrifice child
> [ 82.695110] Killed process 3914 (trinity-c0) total-vm:55864kB, anon-rss:1512kB, file-rss:1088kB, shmem-rss:25616kB
> [ 82.706724] oom_reaper: reaped process 3914 (trinity-c0), now anon-rss:0kB, file-rss:0kB, shmem-rss:26488kB
> [ 82.715540] oom_reaper: reaped process 3914 (trinity-c0), now anon-rss:0kB, file-rss:0kB, shmem-rss:26900kB
> [ 82.717662] oom_reaper: reaped process 3914 (trinity-c0), now anon-rss:0kB, file-rss:0kB, shmem-rss:26900kB
> [ 82.725804] oom_reaper: reaped process 3914 (trinity-c0), now anon-rss:0kB, file-rss:0kB, shmem-rss:27296kB
> [ 82.739091] oom_reaper: reaped process 3914 (trinity-c0), now anon-rss:0kB, file-rss:0kB, shmem-rss:28148kB
>
> oom_reaper is trying to reap the same task again and again. This
> is possible only when the oom killer is bypassed because of
> task_will_free_mem because we skip over tasks with MMF_OOM_REAPED
> already set during select_bad_process. Teach task_will_free_mem to skip
> over MMF_OOM_REAPED tasks as well because they will be unlikely to free
> anything more.
I agree that we need to prevent same mm from being selected forever. But I
feel worried about this patch. We are reaching a stage what purpose we set
TIF_MEMDIE for. mark_oom_victim() sets TIF_MEMDIE on a thread with oom_lock
held. Thus, if a mm which the TIF_MEMDIE thread is using is reapable (likely
yes), __oom_reap_task() will likely be the next thread which will get that lock
because __oom_reap_task() uses mutex_lock(&oom_lock) whereas other threads
using that mm use mutex_trylock(&oom_lock). As a result, regarding CONFIG_MMU=y
kernels, I guess that
if (task_will_free_mem(current)) {
shortcut in out_of_memory() likely becomes an useless condition. Since the OOM
reaper will quickly reap mm and set MMF_OOM_REAPED on that mm and clear
TIF_MEMDIE, other threads using that mm will fail to get TIF_MEMDIE (because
task_will_free_mem() will start returning false due to this patch) and proceed
to next OOM victim selection. The comment
* That thread will now get access to memory reserves since it has a
* pending fatal signal.
in oom_kill_process() became almost dead. Since we need a short delay in order
to allow get_page_from_freelist() to allocate from memory reclaimed by
__oom_reap_task(), this patch might increase possibility of excessively
preventing OOM-killed threads from using ALLOC_NO_WATERMARKS via TIF_MEMDIE
and increase possibility of needlessly selecting next OOM victim.
So, maybe we shouldn't let this shortcut to return false as soon as
MMF_OOM_REAPED is set.
next prev parent reply other threads:[~2016-06-17 11:35 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-09 11:52 [PATCH 0/10 -v4] Handle oom bypass more gracefully Michal Hocko
2016-06-09 11:52 ` [PATCH 01/10] proc, oom: drop bogus task_lock and mm check Michal Hocko
2016-06-09 11:52 ` [PATCH 02/10] proc, oom: drop bogus sighand lock Michal Hocko
2016-06-09 11:52 ` [PATCH 03/10] proc, oom_adj: extract oom_score_adj setting into a helper Michal Hocko
2016-06-09 11:52 ` [PATCH 04/10] mm, oom_adj: make sure processes sharing mm have same view of oom_score_adj Michal Hocko
2016-06-15 15:03 ` Oleg Nesterov
2016-06-09 11:52 ` [PATCH 05/10] mm, oom: skip vforked tasks from being selected Michal Hocko
2016-06-15 14:51 ` Oleg Nesterov
2016-06-16 6:24 ` Michal Hocko
2016-06-09 11:52 ` [PATCH 06/10] mm, oom: kill all tasks sharing the mm Michal Hocko
2016-06-09 11:52 ` [PATCH 07/10] mm, oom: fortify task_will_free_mem Michal Hocko
2016-06-09 13:18 ` Tetsuo Handa
2016-06-09 14:20 ` Michal Hocko
2016-06-11 8:10 ` Tetsuo Handa
2016-06-13 11:27 ` Michal Hocko
2016-06-16 12:54 ` Tetsuo Handa
2016-06-16 14:29 ` Michal Hocko
2016-06-16 15:40 ` Tetsuo Handa
2016-06-16 15:53 ` Michal Hocko
2016-06-17 11:38 ` Tetsuo Handa
2016-06-17 12:26 ` Michal Hocko
2016-06-17 13:12 ` Tetsuo Handa
2016-06-17 13:29 ` Michal Hocko
2016-06-09 11:52 ` [PATCH 08/10] mm, oom: task_will_free_mem should skip oom_reaped tasks Michal Hocko
2016-06-17 11:35 ` Tetsuo Handa [this message]
2016-06-17 12:56 ` Michal Hocko
2016-06-09 11:52 ` [PATCH 09/10] mm, oom_reaper: do not attempt to reap a task more than twice Michal Hocko
2016-06-15 14:48 ` Oleg Nesterov
2016-06-16 6:28 ` Michal Hocko
2016-06-09 11:52 ` [PATCH 10/10] mm, oom: hide mm which is shared with kthread or global init Michal Hocko
2016-06-09 15:15 ` Tetsuo Handa
2016-06-09 15:41 ` Michal Hocko
2016-06-16 13:15 ` Tetsuo Handa
2016-06-16 13:36 ` Tetsuo Handa
2016-06-15 14:37 ` Oleg Nesterov
2016-06-16 6:31 ` Michal Hocko
2016-06-13 11:23 ` [PATCH 0/10 -v4] Handle oom bypass more gracefully Michal Hocko
2016-06-13 14:13 ` Michal Hocko
2016-06-14 20:17 ` Oleg Nesterov
2016-06-14 20:44 ` Oleg Nesterov
2016-06-16 6:33 ` Michal Hocko
2016-06-15 15:09 ` Oleg Nesterov
2016-06-16 6:34 ` Michal Hocko
-- strict thread matches above, loose matches on Subject: below --
2016-06-20 12:43 [PATCH 0/10 -v5] " Michal Hocko
2016-06-20 12:43 ` [PATCH 08/10] mm, oom: task_will_free_mem should skip oom_reaped tasks Michal Hocko
2016-06-03 9:16 [PATCH 0/10 -v3] Handle oom bypass more gracefully Michal Hocko
2016-06-03 9:16 ` [PATCH 08/10] mm, oom: task_will_free_mem should skip oom_reaped tasks Michal Hocko
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