linux-kernel - Re: [RFC PATCH] memcg, oom: throttle dump_header for memcg ooms without eligible tasks

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Date:   Sat, 13 Oct 2018 20:28:38 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
To:     Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>
Cc:     linux-mm@...ck.org, syzkaller-bugs@...glegroups.com, guro@...com,
        kirill.shutemov@...ux.intel.com, linux-kernel@...r.kernel.org,
        rientjes@...gle.com, yang.s@...baba-inc.com,
        Andrew Morton <akpm@...ux-foundation.org>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [RFC PATCH] memcg, oom: throttle dump_header for memcg ooms
 without eligible tasks

On 2018/10/13 20:22, Johannes Weiner wrote:
> On Sat, Oct 13, 2018 at 08:09:30PM +0900, Tetsuo Handa wrote:
>> ---------- Michal's patch ----------
>>
>> 73133 lines (5.79MB) of kernel messages per one run
>>
>> [root@...ecurity ~]# time ./a.out
>>
>> real    3m44.389s
>> user    0m0.000s
>> sys     3m42.334s
>>
>> [root@...ecurity ~]# time ./a.out
>>
>> real    3m41.767s
>> user    0m0.004s
>> sys     3m39.779s
>>
>> ---------- My v2 patch ----------
>>
>> 50 lines (3.40 KB) of kernel messages per one run
>>
>> [root@...ecurity ~]# time ./a.out
>>
>> real    0m5.227s
>> user    0m0.000s
>> sys     0m4.950s
>>
>> [root@...ecurity ~]# time ./a.out
>>
>> real    0m5.249s
>> user    0m0.000s
>> sys     0m4.956s
> 
> Your patch is suppressing information that I want to have and my
> console can handle, just because your console is slow, even though
> there is no need to use that console at that log level.

My patch is not suppressing information you want to have.
My patch is mainly suppressing

[   52.393146] Out of memory and no killable processes...
[   52.395195] a.out invoked oom-killer: gfp_mask=0x6000c0(GFP_KERNEL), nodemask=(null), order=0, oom_score_adj=-1000
[   52.398623] Out of memory and no killable processes...
[   52.401195] a.out invoked oom-killer: gfp_mask=0x6000c0(GFP_KERNEL), nodemask=(null), order=0, oom_score_adj=-1000
[   52.404356] Out of memory and no killable processes...
[   52.406492] a.out invoked oom-killer: gfp_mask=0x6000c0(GFP_KERNEL), nodemask=(null), order=0, oom_score_adj=-1000
[   52.409595] Out of memory and no killable processes...
[   52.411745] a.out invoked oom-killer: gfp_mask=0x6000c0(GFP_KERNEL), nodemask=(null), order=0, oom_score_adj=-1000
[   52.415588] Out of memory and no killable processes...
[   52.418484] a.out invoked oom-killer: gfp_mask=0x6000c0(GFP_KERNEL), nodemask=(null), order=0, oom_score_adj=-1000
[   52.421904] Out of memory and no killable processes...
[   52.424273] a.out invoked oom-killer: gfp_mask=0x6000c0(GFP_KERNEL), nodemask=(null), order=0, oom_score_adj=-1000

lines which Michal's patch cannot suppress.

Also, my console is console=ttyS0,115200n8 . Not slow at all.

> 
> NAK to your patch. I think you're looking at this from the wrong
> angle. A console that takes almost 4 minutes to print 70k lines
> shouldn't be the baseline for how verbose KERN_INFO is.
> 

Run the testcase in your environment.