Re: [PATCH] mm: memcontrol: print proper OOM header when no eligible victim left

[Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>]

On 2018/08/22 1:04, Johannes Weiner wrote:
> When the memcg OOM killer runs out of killable tasks, it currently
> prints a WARN with no further OOM context. This has caused some user
> confusion.
> 
> Warnings indicate a kernel problem. In a reported case, however, the
> situation was triggered by a non-sensical memcg configuration (hard
> limit set to 0). But without any VM context this wasn't obvious from
> the report, and it took some back and forth on the mailing list to
> identify what is actually a trivial issue.
> 
> Handle this OOM condition like we handle it in the global OOM killer:
> dump the full OOM context and tell the user we ran out of tasks.
> 
> This way the user can identify misconfigurations easily by themselves
> and rectify the problem - without having to go through the hassle of
> running into an obscure but unsettling warning, finding the
> appropriate kernel mailing list and waiting for a kernel developer to
> remote-analyze that the memcg configuration caused this.
> 
> If users cannot make sense of why the OOM killer was triggered or why
> it failed, they will still report it to the mailing list, we know that
> from experience. So in case there is an actual kernel bug causing
> this, kernel developers will very likely hear about it.
> 
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
> Acked-by: Michal Hocko <mhocko@suse.com>
> ---
>  mm/memcontrol.c |  2 --
>  mm/oom_kill.c   | 13 ++++++++++---
>  2 files changed, 10 insertions(+), 5 deletions(-)
> 

Now that above patch went to 4.19-rc3, please apply below one.