linux-kernel - Re: [PATCH v2] mm: oom: deduplicate victim selection code for memcg and global oom

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Message-ID: <alpine.DEB.2.10.1606271713320.81440@chino.kir.corp.google.com>
Date:	Mon, 27 Jun 2016 17:14:31 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Vladimir Davydov <vdavydov@...tuozzo.com>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Michal Hocko <mhocko@...nel.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] mm: oom: deduplicate victim selection code for memcg
 and global oom

On Mon, 27 Jun 2016, Vladimir Davydov wrote:

> When selecting an oom victim, we use the same heuristic for both memory
> cgroup and global oom. The only difference is the scope of tasks to
> select the victim from. So we could just export an iterator over all
> memcg tasks and keep all oom related logic in oom_kill.c, but instead we
> duplicate pieces of it in memcontrol.c reusing some initially private
> functions of oom_kill.c in order to not duplicate all of it. That looks
> ugly and error prone, because any modification of select_bad_process
> should also be propagated to mem_cgroup_out_of_memory.
> 
> Let's rework this as follows: keep all oom heuristic related code
> private to oom_kill.c and make oom_kill.c use exported memcg functions
> when it's really necessary (like in case of iterating over memcg tasks).
> 

I don't know how others feel, but this actually turns out harder to read 
for me with all the extra redirection with minimal savings (a few dozen 
lines of code).