linux-kernel - Re: [PATCH] ring-buffer: Add set/clear_current_oom

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Date:   Wed, 4 Apr 2018 16:59:18 -0700
From:   Joel Fernandes <joelaf@...gle.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Michal Hocko <mhocko@...nel.org>,
        Zhaoyang Huang <huangzhaoyang@...il.com>,
        Ingo Molnar <mingo@...nel.org>,
        kernel-patch-test@...ts.linaro.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        "open list:MEMORY MANAGEMENT" <linux-mm@...ck.org>,
        Vlastimil Babka <vbabka@...e.cz>
Subject: Re: [PATCH] ring-buffer: Add set/clear_current_oom_origin() during allocations

Hi Steve,

On Wed, Apr 4, 2018 at 9:18 AM, Joel Fernandes <joelaf@...gle.com> wrote:
> On Wed, Apr 4, 2018 at 9:13 AM, Steven Rostedt <rostedt@...dmis.org> wrote:
> [..]
>>>
>>> Also, I agree with the new patch and its nice idea to do that.
>>
>> Thanks, want to give it a test too?

With the latest tree and the below diff, I can still OOM-kill a victim
process doing a large buffer_size_kb write:

I pulled your ftrace/core and added this:
+       /*
        i = si_mem_available();
        if (i < nr_pages)
                return -ENOMEM;
+       */

Here's a run in Qemu with 4-cores 1GB total memory:

bash-4.3# ./m -m 1M &
[1] 1056
bash-4.3#
bash-4.3#
bash-4.3#
bash-4.3# echo 10000000 > /d/tracing/buffer_size_kb
[   33.213988] Out of memory: Kill process 1042 (bash) score
1712050900 or sacrifice child
[   33.215349] Killed process 1056 (m) total-vm:9220kB,
anon-rss:7564kB, file-rss:4kB, shmem-rss:640kB
bash: echo: write error: Cannot allocate memory
[1]+  Killed                  ./m -m 1M
bash-4.3#
--

As you can see, OOM killer triggers and kills "m" which is my busy
memory allocator (it allocates and frees lots of memory and does that
in a loop)

Here's the m program, sorry if it looks too ugly:
https://pastebin.com/raw/aG6Qw37Z

Happy to try anything else, BTW when the si_mem_available check
enabled, this doesn't happen and the buffer_size_kb write fails
normally without hurting anything else.

- Joel