linux-kernel - Re: [PATCH 1/2] mm, oom: introduce oom reaper

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Date:	Mon, 21 Dec 2015 15:38:21 -0500
From:	Paul Gortmaker <paul.gortmaker@...driver.com>
To:	Michal Hocko <mhocko@...nel.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>,
	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
	David Rientjes <rientjes@...gle.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Hugh Dickins <hughd@...gle.com>,
	Andrea Argangeli <andrea@...nel.org>,
	Rik van Riel <riel@...hat.com>, linux-mm@...ck.org,
	LKML <linux-kernel@...r.kernel.org>,
	Michal Hocko <mhocko@...e.com>
Subject: Re: [PATCH 1/2] mm, oom: introduce oom reaper

On Tue, Dec 15, 2015 at 1:36 PM, Michal Hocko <mhocko@...nel.org> wrote:
> From: Michal Hocko <mhocko@...e.com>
>
> This is based on the idea from Mel Gorman discussed during LSFMM 2015 and
> independently brought up by Oleg Nesterov.
>

[...]

Since this is built-in always, can we....

> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index 5314b206caa5..48025a21f8c4 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -35,6 +35,11 @@
>  #include <linux/freezer.h>
>  #include <linux/ftrace.h>
>  #include <linux/ratelimit.h>
> +#include <linux/kthread.h>
> +#include <linux/module.h>

...use <linux/init.h> instead above, and then...

> +
> +#include <asm/tlb.h>
> +#include "internal.h"
>

[...]

> +                * Make sure our oom reaper thread will get scheduled when
> +                * ASAP and that it won't get preempted by malicious userspace.
> +                */
> +               sched_setscheduler(oom_reaper_th, SCHED_FIFO, &param);
> +       }
> +       return 0;
> +}
> +module_init(oom_init)

...use one of the non-modular initcalls here?   I'm trying to clean up most of
the non-modular uses of modular macros etc. since:

 (1) it is easy to accidentally code up an unused module_exit function
 (2) it can be misleading when reading the source, thinking it can be
      modular when the Makefile and/or Kconfig prohibit it
 (3) it requires the include of the module.h header file which in turn
     includes nearly everything else, thus increasing CPP overhead.

I figured no point in sending a follow on patch since this came in via
the akpm tree into next and that gets rebased/updated regularly.

Thanks,
Paul.
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