From: Qian Cai <cai@lca.pw>
To: Michal Hocko <mhocko@kernel.org>, linux-mm@kvack.org
Cc: Andrew Morton <akpm@linux-foundation.org>,
Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
David Rientjes <rientjes@google.com>,
LKML <linux-kernel@vger.kernel.org>,
Michal Hocko <mhocko@suse.com>
Subject: Re: [RFC PATCH] mm, oom: disable dump_tasks by default
Date: Tue, 03 Sep 2019 11:02:46 -0400 [thread overview]
Message-ID: <1567522966.5576.51.camel@lca.pw> (raw)
In-Reply-To: <20190903144512.9374-1-mhocko@kernel.org>
On Tue, 2019-09-03 at 16:45 +0200, Michal Hocko wrote:
> From: Michal Hocko <mhocko@suse.com>
>
> dump_tasks has been introduced by quite some time ago fef1bdd68c81
> ("oom: add sysctl to enable task memory dump"). It's primary purpose is
> to help analyse oom victim selection decision. This has been certainly
> useful at times when the heuristic to chose a victim was much more
> volatile. Since a63d83f427fb ("oom: badness heuristic rewrite")
> situation became much more stable (mostly because the only selection
> criterion is the memory usage) and reports about a wrong process to
> be shot down have become effectively non-existent.
Well, I still see OOM sometimes kills wrong processes like ssh, systemd
processes while LTP OOM tests with staight-forward allocation patterns. I just
have not had a chance to debug them fully. The situation could be worse with
more complex allocations like random stress or fuzzy testing.
>
> dump_tasks can generate a lot of output to the kernel log. It is not
> uncommon that even relative small system has hundreds of tasks running.
> Generating a lot of output to the kernel log both makes the oom report
> less convenient to process and also induces a higher load on the printk
> subsystem which can lead to other problems (e.g. longer stalls to flush
> all the data to consoles).
It is only generate output for the victim process where I tested on those large
NUMA machines and the output is fairly manageable.
>
> Therefore change the default of oom_dump_tasks to not print the task
> list by default. The sysctl remains in place for anybody who might need
> to get this additional information. The oom report still provides an
> information about the allocation context and the state of the MM
> subsystem which should be sufficient to analyse most of the oom
> situations.
>
> Signed-off-by: Michal Hocko <mhocko@suse.com>
> ---
> mm/oom_kill.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index eda2e2a0bdc6..d0353705c6e6 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -52,7 +52,7 @@
>
> int sysctl_panic_on_oom;
> int sysctl_oom_kill_allocating_task;
> -int sysctl_oom_dump_tasks = 1;
> +int sysctl_oom_dump_tasks;
>
> /*
> * Serializes oom killer invocations (out_of_memory()) from all contexts to
next prev parent reply other threads:[~2019-09-03 15:02 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-03 14:45 [RFC PATCH] mm, oom: disable dump_tasks by default Michal Hocko
2019-09-03 15:02 ` Qian Cai [this message]
2019-09-03 15:13 ` Michal Hocko
2019-09-03 15:32 ` Qian Cai
2019-09-03 19:12 ` Michal Hocko
2019-09-05 16:10 ` Qian Cai
2019-09-03 20:52 ` Tetsuo Handa
2019-09-04 5:40 ` Michal Hocko
2019-09-04 20:04 ` David Rientjes
2019-09-05 13:39 ` Tetsuo Handa
2019-09-05 14:08 ` Michal Hocko
2019-09-06 10:46 ` Tetsuo Handa
2019-09-06 11:02 ` Michal Hocko
2019-09-06 11:11 ` Tetsuo Handa
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