From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Vladimir Davydov <vdavydov.dev@gmail.com>,
linux-mm@kvack.org, Greg Thelen <gthelen@google.com>,
Dmitry Vyukov <dvyukov@google.com>,
LKML <linux-kernel@vger.kernel.org>,
Michal Hocko <mhocko@suse.com>,
David Rientjes <rientjes@google.com>
Subject: Re: [PATCH] memcg, oom: be careful about races when warning about no reclaimable task
Date: Wed, 8 Aug 2018 21:57:13 +0900 [thread overview]
Message-ID: <9cea37c8-ab90-2fdf-395c-efe52ff07072@i-love.sakura.ne.jp> (raw)
In-Reply-To: <1308e0bd-e194-7b35-484c-fc18f493f8da@i-love.sakura.ne.jp>
On 2018/08/08 5:38, Tetsuo Handa wrote:
> On 2018/08/08 5:19, Johannes Weiner wrote:
>> On Tue, Aug 07, 2018 at 07:15:11PM +0900, Tetsuo Handa wrote:
>>> On 2018/08/07 16:25, Michal Hocko wrote:
>>>> @@ -1703,7 +1703,8 @@ static enum oom_status mem_cgroup_oom(struct mem_cgroup *memcg, gfp_t mask, int
>>>> return OOM_ASYNC;
>>>> }
>>>>
>>>> - if (mem_cgroup_out_of_memory(memcg, mask, order))
>>>> + if (mem_cgroup_out_of_memory(memcg, mask, order) ||
>>>> + tsk_is_oom_victim(current))
>>>> return OOM_SUCCESS;
>>>>
>>>> WARN(1,"Memory cgroup charge failed because of no reclaimable memory! "
>>>>
>>>
>>> I don't think this patch is appropriate. This patch only avoids hitting WARN(1).
>>> This patch does not address the root cause:
>>>
>>> The task_will_free_mem(current) test in out_of_memory() is returning false
>>> because test_bit(MMF_OOM_SKIP, &mm->flags) test in task_will_free_mem() is
>>> returning false because MMF_OOM_SKIP was already set by the OOM reaper. The OOM
>>> killer does not need to start selecting next OOM victim until "current thread
>>> completes __mmput()" or "it fails to complete __mmput() within reasonable
>>> period".
>>
>> I don't see why it matters whether the OOM victim exits or not, unless
>> you count the memory consumed by struct task_struct.
>
> We are not counting memory consumed by struct task_struct. But David is
> counting memory released between set_bit(MMF_OOM_SKIP, &mm->flags) and
> completion of exit_mmap().
Also, before the OOM reaper was introduced, we waited until TIF_MEMDIE is
cleared from the OOM victim thread. Compared to pre OOM reaper era, giving up
so early is certainly a regression.
next prev parent reply other threads:[~2018-08-08 12:57 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-07 7:25 [PATCH] memcg, oom: be careful about races when warning about no reclaimable task Michal Hocko
2018-08-07 10:15 ` Tetsuo Handa
2018-08-07 11:04 ` Michal Hocko
2018-08-07 20:19 ` Johannes Weiner
2018-08-07 20:38 ` Tetsuo Handa
2018-08-08 12:57 ` Tetsuo Handa [this message]
2018-08-08 13:16 ` Michal Hocko
2018-08-07 20:02 ` Johannes Weiner
2018-08-07 20:23 ` Michal Hocko
2018-08-07 20:54 ` Johannes Weiner
2018-08-08 6:44 ` Michal Hocko
2018-08-08 7:12 ` Michal Hocko
2018-08-08 7:13 ` [PATCH 1/2] " Michal Hocko
2018-08-08 7:13 ` [PATCH 2/2] memcg, oom: emit oom report when there is no eligible task Michal Hocko
2018-08-08 14:45 ` Johannes Weiner
2018-08-08 16:17 ` Michal Hocko
2018-08-21 14:06 ` Michal Hocko
2018-08-21 17:20 ` Johannes Weiner
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