linux-kernel - Re: [patch] oom: document obsolete oom

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Date:	Mon, 15 Nov 2010 09:22:27 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	David Rientjes <rientjes@...gle.com>
Cc:	kosaki.motohiro@...fujitsu.com,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [patch] oom: document obsolete oom_adj tunable

> /proc/pid/oom_adj was deprecated in August 2010 with the introduction of
> the new oom killer heuristic.
> 
> This patch copies the Documentation/feature-removal-schedule.txt entry
> for this tunable to the Documentation/ABI/obsolete directory so nobody
> misses it.
> 
> Reported-by: Alan Cox <alan@...rguk.ukuu.org.uk>
> Signed-off-by: David Rientjes <rientjes@...gle.com>

NAK. You seems to think shouting claim makes some effect. but It's incorrect.
Your childish shout doesn't solve any real world issue. Only code fix does.


> ---
>  Documentation/ABI/obsolete/proc-pid-oom_adj |   22 ++++++++++++++++++++++
>  1 files changed, 22 insertions(+), 0 deletions(-)
>  create mode 100644 Documentation/ABI/obsolete/proc-pid-oom_adj
> 
> diff --git a/Documentation/ABI/obsolete/proc-pid-oom_adj b/Documentation/ABI/obsolete/proc-pid-oom_adj
> new file mode 100644
> --- /dev/null
> +++ b/Documentation/ABI/obsolete/proc-pid-oom_adj
> @@ -0,0 +1,22 @@
> +What:	/proc/<pid>/oom_adj
> +When:	August 2012
> +Why:	/proc/<pid>/oom_adj allows userspace to influence the oom killer's
> +	badness heuristic used to determine which task to kill when the kernel
> +	is out of memory.
> +
> +	The badness heuristic has since been rewritten since the introduction of
> +	this tunable such that its meaning is deprecated.  The value was
> +	implemented as a bitshift on a score generated by the badness()
> +	function that did not have any precise units of measure.  With the
> +	rewrite, the score is given as a proportion of available memory to the
> +	task allocating pages, so using a bitshift which grows the score
> +	exponentially is, thus, impossible to tune with fine granularity.
> +
> +	A much more powerful interface, /proc/<pid>/oom_score_adj, was
> +	introduced with the oom killer rewrite that allows users to increase or
> +	decrease the badness() score linearly.  This interface will replace
> +	/proc/<pid>/oom_adj.

Incorrect. oom_adj and oom_score_adj have different concept and different abstraction.
One can't replace another.

> +
> +	A warning will be emitted to the kernel log if an application uses this
> +	deprecated interface.  After it is printed once, future warnings will be
> +	suppressed until the kernel is rebooted.





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