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From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
To: Michal Hocko <mhocko@kernel.org>
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>
Subject: Re: [RFC PATCH] memcg, oom: throttle dump_header for memcg ooms without eligible tasks
Date: Mon, 15 Oct 2018 21:47:08 +0900	[thread overview]
Message-ID: <6c0a57b3-bfd4-d832-b0bd-5dd3bcae460e@i-love.sakura.ne.jp> (raw)
In-Reply-To: <20181015112427.GI18839@dhcp22.suse.cz>

On 2018/10/15 20:24, Michal Hocko wrote:
> On Mon 15-10-18 19:57:35, Tetsuo Handa wrote:
>> On 2018/10/15 17:19, Michal Hocko wrote:
>>> As so many dozens of times before, I will point you to an incremental
>>> nature of changes we really prefer in the mm land. We are also after a
>>> simplicity which your proposal lacks in many aspects. You seem to ignore
>>> that general approach and I have hard time to consider your NAK as a
>>> relevant feedback. Going to an extreme and basing a complex solution on
>>> it is not going to fly. No killable process should be a rare event which
>>> requires a seriously misconfigured memcg to happen so wildly. If you can
>>> trigger it with a normal user privileges then it would be a clear bug to
>>> address rather than work around with printk throttling.
>>>
>>
>> I can trigger 200+ times / 900+ lines / 69KB+ of needless OOM messages
>> with a normal user privileges. This is a lot of needless noise/delay.
> 
> I am pretty sure you have understood the part of my message you have
> chosen to not quote where I have said that the specific rate limitting
> decisions can be changed based on reasonable configurations. There is
> absolutely zero reason to NAK a natural decision to unify the throttling
> and cook a per-memcg way for a very specific path instead.
> 
>> No killable process is not a rare event, even without root privileges.
>>
>> [root@ccsecurity kumaneko]# time ./a.out
>> Killed
>>
>> real    0m2.396s
>> user    0m0.000s
>> sys     0m2.970s
>> [root@ccsecurity ~]# dmesg | grep 'no killable' | wc -l
>> 202
>> [root@ccsecurity ~]# dmesg | wc
>>     942    7335   70716
> 
> OK, so this is 70kB worth of data pushed throug the console. Is this
> really killing any machine?
> 

Nobody can prove that it never kills some machine. This is just one example result of
one example stress tried in my environment. Since I am secure programming man from security
subsystem, I really hate your "Can you trigger it?" resistance. Since this is OOM path
where nobody tests, starting from being prepared for the worst case keeps things simple.

  reply	other threads:[~2018-10-15 12:47 UTC|newest]

Thread overview: 42+ 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
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
2018-10-10 15:11   ` Michal Hocko
2018-10-11  6:37   ` Tetsuo Handa
2018-10-11  6:37     ` Tetsuo Handa
2018-10-12 10:47     ` 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 [this message]
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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