linux-kernel - Re: [patch v2] mm, oom: fix concurrent munlock and oom reaperunmap

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Message-Id: <201804221248.CHE35432.FtOMOLSHOFJFVQ@I-love.SAKURA.ne.jp>
Date:   Sun, 22 Apr 2018 12:48:13 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:     rientjes@...gle.com, mhocko@...nel.org
Cc:     akpm@...ux-foundation.org, aarcange@...hat.com, guro@...com,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [patch v2] mm, oom: fix concurrent munlock and oom reaperunmap

David Rientjes wrote:
> How have you tested this?
> 
> I'm wondering why you do not see oom killing of many processes if the 
> victim is a very large process that takes a long time to free memory in 
> exit_mmap() as I do because the oom reaper gives up trying to acquire 
> mm->mmap_sem and just sets MMF_OOM_SKIP itself.
> 

We can call __oom_reap_task_mm() from exit_mmap() (or __mmput()) before
exit_mmap() holds mmap_sem for write. Then, at least memory which could
have been reclaimed if exit_mmap() did not hold mmap_sem for write will
be guaranteed to be reclaimed before MMF_OOM_SKIP is set.