linux-kernel - Re: [PATCH v3] mm: memcontrol: Don't flood OOM messages with no eligible task.

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Date:   Fri, 19 Oct 2018 08:54:27 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Michal Hocko <mhocko@...nel.org>,
        Johannes Weiner <hannes@...xchg.org>, linux-mm@...ck.org,
        syzkaller-bugs@...glegroups.com, guro@...com,
        kirill.shutemov@...ux.intel.com, linux-kernel@...r.kernel.org,
        rientjes@...gle.com, yang.s@...baba-inc.com,
        Andrew Morton <akpm@...ux-foundation.org>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        syzbot <syzbot+77e6b28a7a7106ad0def@...kaller.appspotmail.com>
Subject: Re: [PATCH v3] mm: memcontrol: Don't flood OOM messages with no
 eligible task.

On (10/18/18 20:58), Tetsuo Handa wrote:
> > 
> > A knob might do.
> > As well as /proc/sys/kernel/printk tweaks, probably. One can even add
> > echo "a b c d" > /proc/sys/kernel/printk to .bashrc and adjust printk
> > console levels on login and rollback to old values in .bash_logout
> > May be.
> 
> That can work for only single login with root user case.
> Not everyone logs into console as root user.

Add sudo ;)

> It is pity that we can't send kernel messages to only selected consoles
> (e.g. all messages are sent to netconsole, but only critical messages are
> sent to local consoles).

OK, that's a fair point. There was a patch from FB, which would allow us
to set a log_level on per-console basis. So the noise goes to heav^W net
console; only critical stuff goes to the serial console (if I recall it
correctly). I'm not sure what happened to that patch, it was a while ago.
I'll try to find that out.

[..]
> That boils down to a "user interaction" problem.
> Not limiting
> 
>   "%s invoked oom-killer: gfp_mask=%#x(%pGg), nodemask=%*pbl, order=%d, oom_score_adj=%hd\n"
>   "Out of memory and no killable processes...\n"
> 
> is very annoying.
> 
> And I really can't understand why Michal thinks "handling this requirement" as
> "make the code more complex than necessary and squash different things together".

Michal is trying very hard to address the problem in a reasonable way.
The problem you are talking about is not MM specific. You can have a
faulty SCSI device, corrupted FS, and so and on.

	-ss