From: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
To: Dmitry Vyukov <dvyukov@google.com>, Michal Hocko <mhocko@kernel.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
syzbot <syzbot+77e6b28a7a7106ad0def@syzkaller.appspotmail.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Andrew Morton <akpm@linux-foundation.org>,
guro@fb.com,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
LKML <linux-kernel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>,
David Rientjes <rientjes@google.com>,
syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
Yang Shi <yang.s@alibaba-inc.com>,
Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
Petr Mladek <pmladek@suse.com>
Subject: Re: INFO: rcu detected stall in shmem_fault
Date: Thu, 11 Oct 2018 00:17:29 +0900 [thread overview]
Message-ID: <20181010151729.GC3949@tigerII.localdomain> (raw)
In-Reply-To: <CACT4Y+ZfVdeB-WNeLCWJvTHNeCUtR3r1R+3Qjv9XjZXPxaV2WA@mail.gmail.com>
On (10/10/18 14:29), Dmitry Vyukov wrote:
> >> A bit unrelated, but while we are at it:
> >>
> >> I like it when we rate-limit printk-s that lookup the system.
> >> But it seems that default rate-limit values are not always good enough,
> >> DEFAULT_RATELIMIT_INTERVAL / DEFAULT_RATELIMIT_BURST can still be too
> >> verbose. For instance, when we have a very slow IPMI emulated serial
> >> console -- e.g. baud rate at 57600. DEFAULT_RATELIMIT_INTERVAL and
> >> DEFAULT_RATELIMIT_BURST can add new OOM headers and backtraces faster
> >> than we evict them.
> >>
> >> Does it sound reasonable enough to use larger than default rate-limits
> >> for printk-s in OOM print-outs? OOM reports tend to be somewhat large
> >> and the reported numbers are not always *very* unique.
> >>
> >> What do you think?
> >
> > I do not really care about the current inerval/burst values. This change
> > should be done seprately and ideally with some numbers.
>
> I think Sergey meant that this place may need to use
> larger-than-default values because it prints lots of output per
> instance (whereas the default limit is more tuned for cases that print
> just 1 line).
>
> I've found at least 1 place that uses DEFAULT_RATELIMIT_INTERVAL*10:
> https://elixir.bootlin.com/linux/latest/source/fs/btrfs/extent-tree.c#L8365
> Probably we need something similar here.
Yes, Dmitry, that's what I meant - to use something like
DEFAULT_RATELIMIT_INTERVAL * 10 in OOM. I didn't mean to change
the default values system wide.
---
We are not rate-limiting a single annoying printk() in OOM, but
functions that do a whole bunch of printks - OOM header, backtraces, etc.
Thus OOM report can be, I don't know, 50 or 70 or 100 lines (who knows).
So that's why rate-limit in OOM is more permissive in terms of number of
printed lines. When we rate-limit a single printk() we let 10 prinks()
/*10 lines*/ max every 5 seconds. While in OOM this transforms into
10 dump_header() + 10 oom_kill_process() every 5 seconds. Still can be
too many printk()-s, enough to lockup the system.
-ss
next prev parent reply other threads:[~2018-10-10 15:17 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-10 0:08 INFO: rcu detected stall in shmem_fault syzbot
2018-10-10 0:12 ` Tetsuo Handa
2018-10-10 4:11 ` David Rientjes
2018-10-10 7:55 ` Dmitry Vyukov
2018-10-10 9:13 ` Michal Hocko
2018-10-10 9:33 ` Dmitry Vyukov
2018-10-10 9:02 ` Michal Hocko
2018-10-10 8:59 ` Michal Hocko
2018-10-10 10:43 ` Tetsuo Handa
2018-10-10 11:35 ` Michal Hocko
2018-10-10 11:48 ` Sergey Senozhatsky
2018-10-10 12:25 ` Michal Hocko
2018-10-10 12:29 ` Dmitry Vyukov
2018-10-10 12:36 ` Dmitry Vyukov
2018-10-10 13:10 ` Tetsuo Handa
2018-10-10 13:17 ` Dmitry Vyukov
2018-10-11 1:17 ` Sergey Senozhatsky
2018-10-10 15:17 ` Sergey Senozhatsky [this message]
2018-10-10 14:19 ` Tetsuo Handa
2018-10-10 15:11 ` [RFC PATCH] memcg, oom: throttle dump_header for memcg ooms without eligible tasks Michal Hocko
2018-10-11 6:37 ` Tetsuo Handa
2018-10-12 10:47 ` Tetsuo Handa
2018-10-12 11:20 ` Johannes Weiner
2018-10-12 12:08 ` Michal Hocko
2018-10-12 12:10 ` Tetsuo Handa
2018-10-12 12:41 ` Johannes Weiner
2018-10-12 12:58 ` Tetsuo Handa
2018-10-13 11:09 ` Tetsuo Handa
2018-10-13 11:22 ` Johannes Weiner
2018-10-13 11:28 ` Tetsuo Handa
2018-10-15 8:19 ` Michal Hocko
2018-10-15 10:57 ` Tetsuo Handa
2018-10-15 11:24 ` Michal Hocko
2018-10-15 12:47 ` Tetsuo Handa
2018-10-15 13:35 ` Michal Hocko
2018-10-16 0:55 ` Tetsuo Handa
2018-10-16 9:20 ` Michal Hocko
2018-10-16 11:05 ` Tetsuo Handa
2018-10-16 11:17 ` Michal Hocko
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