linux-kernel - Re: [PATCH] mm, vmscan: do not loop on too_many

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Date:   Tue, 21 Mar 2017 19:37:39 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:     mhocko@...nel.org, hannes@...xchg.org
Cc:     riel@...hat.com, akpm@...ux-foundation.org, mgorman@...e.de,
        vbabka@...e.cz, linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm, vmscan: do not loop on too_many_isolated for ever

On 2017/03/10 20:44, Tetsuo Handa wrote:
> Michal Hocko wrote:
>> On Thu 09-03-17 13:05:40, Johannes Weiner wrote:
>>>> It may be OK, I just do not understand all the implications.
>>>>
>>>> I like the general direction your patch takes the code in,
>>>> but I would like to understand it better...
>>>
>>> I feel the same way. The throttling logic doesn't seem to be very well
>>> thought out at the moment, making it hard to reason about what happens
>>> in certain scenarios.
>>>
>>> In that sense, this patch isn't really an overall improvement to the
>>> way things work. It patches a hole that seems to be exploitable only
>>> from an artificial OOM torture test, at the risk of regressing high
>>> concurrency workloads that may or may not be artificial.
>>>
>>> Unless I'm mistaken, there doesn't seem to be a whole lot of urgency
>>> behind this patch. Can we think about a general model to deal with
>>> allocation concurrency? 
>>
>> I am definitely not against. There is no reason to rush the patch in.
> 
> I don't hurry if we can check using watchdog whether this problem is occurring
> in the real world. I have to test corner cases because watchdog is missing.

Today I tested linux-next-20170321 with not so insane stress, and I again
hit this problem. Thus, I think this problem might occur in the real world.

http://I-love.SAKURA.ne.jp/tmp/serial-20170321.txt.xz (Logs up to before swapoff are eliminated.)
----------
[ 2250.175109] MemAlloc-Info: stalling=16 dying=0 exiting=4 victim=0 oom_count=1155386
[ 2257.535653] MemAlloc-Info: stalling=16 dying=0 exiting=4 victim=0 oom_count=1155386
[ 2319.806880] MemAlloc-Info: stalling=19 dying=0 exiting=4 victim=0 oom_count=1155386
[ 2320.722282] MemAlloc-Info: stalling=19 dying=0 exiting=4 victim=0 oom_count=1155386
[ 2381.243393] MemAlloc-Info: stalling=20 dying=0 exiting=4 victim=0 oom_count=1155386
[ 2389.777052] MemAlloc-Info: stalling=20 dying=0 exiting=4 victim=0 oom_count=1155386
[ 2450.878287] MemAlloc-Info: stalling=20 dying=0 exiting=4 victim=0 oom_count=1155386
[ 2459.386321] MemAlloc-Info: stalling=20 dying=0 exiting=4 victim=0 oom_count=1155386
[ 2520.500633] MemAlloc-Info: stalling=20 dying=0 exiting=4 victim=0 oom_count=1155386
[ 2529.042088] MemAlloc-Info: stalling=20 dying=0 exiting=4 victim=0 oom_count=1155386
----------