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

From: Sergey Senozhatsky
Date: Thu Oct 18 2018 - 19:54:36 EST

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.