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

From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
	Michal Hocko <mhocko@kernel.org>,
	Johannes Weiner <hannes@cmpxchg.org>,
	linux-mm@kvack.org, syzkaller-bugs@googlegroups.com, guro@fb.com,
	kirill.shutemov@linux.intel.com, linux-kernel@vger.kernel.org,
	rientjes@google.com, yang.s@alibaba-inc.com,
	Andrew Morton <akpm@linux-foundation.org>,
	Petr Mladek <pmladek@suse.com>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	syzbot <syzbot+77e6b28a7a7106ad0def@syzkaller.appspotmail.com>
Subject: Re: [PATCH v3] mm: memcontrol: Don't flood OOM messages with no eligible task.
Date: Fri, 19 Oct 2018 08:54:27 +0900	[thread overview]
Message-ID: <20181018235427.GA877@jagdpanzerIV> (raw)
In-Reply-To: <2c2b2820-e6f8-76c8-c431-18f60845b3ab@i-love.sakura.ne.jp>

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