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From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Michal Hocko <mhocko@kernel.org>,
	Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: 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>,
	Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
	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: Wed, 17 Oct 2018 20:17:24 +0900	[thread overview]
Message-ID: <20181017111724.GA459@jagdpanzerIV> (raw)
In-Reply-To: <20181017102821.GM18839@dhcp22.suse.cz>

On (10/17/18 12:28), Michal Hocko wrote:
> > Michal proposed ratelimiting dump_header() [2]. But I don't think that
> > that patch is appropriate because that patch does not ratelimit
> > 
> >   "%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"
[..]
> > Let's make sure that next dump_header() waits for at least 60 seconds from
> > previous "Out of memory and no killable processes..." message.
> 
> Could you explain why this is any better than using a well established
> ratelimit approach?

Tetsuo, let's use a well established rate-limit approach both in
dump_hedaer() and out_of_memory(). I actually was under impression
that Michal added rate-limiting to both of these functions.

The appropriate rate-limit value looks like something that printk()
should know and be able to tell to the rest of the kernel. I don't
think that middle ground will ever be found elsewhere.


printk() knows what consoles are registered, and printk() also knows
(sometimes) what console="..." options the kernel was provided with.
If baud rates ware not provided as console= options, then serial
consoles usually use some default value. We can probably ask consoles.

So *maybe* we can do something like this

//
// WARNING: this is just a sketch. A silly idea.
//          I don't know if we can make it usable.
//

---

int printk_ratelimit_interval(void)
{
       int ret = DEFAULT_RATELIMIT_INTERVAL;
       struct tty_driver *driver = NULL;
       speed_t min_baud = MAX_INT;

       console_lock();
       for_each_console(c) {
               speed_t br;

               if (!c->device)
                       continue;
               if (!(c->flags & CON_ENABLED))
                       continue;
               if (!c->write)
                       continue;
               driver = c->device(c, index);
               if (!driver)
                       continue;

               br = tty_get_baud_rate(tty_driver to tty_struct [???]);
               min_baud = min(min_baud, br);
       }
       console_unlock();

       switch (min_baud) {
       case 115200:
               return ret;

       case ...blah blah...:
               return ret * 2;

       case 9600:
               return ret * 4;
       }
       return ret;
}

---

	-ss

  reply	other threads:[~2018-10-17 11:17 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-17 10:06 Tetsuo Handa
2018-10-17 10:28 ` Michal Hocko
2018-10-17 11:17   ` Sergey Senozhatsky [this message]
2018-10-17 11:29     ` Michal Hocko
2018-10-18  2:46     ` Tetsuo Handa
2018-10-18  2:46       ` Tetsuo Handa
2018-10-18  4:27       ` Sergey Senozhatsky
2018-10-18  5:26         ` Tetsuo Handa
2018-10-18  5:26           ` Tetsuo Handa
2018-10-18  6:10           ` Sergey Senozhatsky
2018-10-18  7:56             ` Michal Hocko
2018-10-18  8:13               ` Sergey Senozhatsky
2018-10-18 11:58                 ` Tetsuo Handa
2018-10-18 23:54                   ` Sergey Senozhatsky
2018-10-19 10:35                     ` Tetsuo Handa
2018-10-19 10:35                       ` Tetsuo Handa
2018-10-23  0:47                       ` Sergey Senozhatsky
2018-10-23  8:37                       ` Petr Mladek
2018-10-23  8:54                         ` Michal Hocko
2018-10-18 14:30         ` Petr Mladek
2018-10-19  0:18           ` Tetsuo Handa
2018-10-23  8:21             ` Petr Mladek
2018-10-23 10:23               ` Tetsuo Handa
2018-10-18  6:55       ` Michal Hocko
2018-10-18 10:37         ` Tetsuo Handa
2018-10-18 11:23           ` Michal Hocko

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