linux-kernel - Re: [patch] mm: disable user interface to manually rescue unevictable pages

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Date:	Wed, 28 Sep 2011 13:51:38 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Johannes Weiner <jweiner@...hat.com>
Cc:	Andrew Morton <akpm@...gle.com>,
	Kautuk Consul <consul.kautuk@...il.com>,
	Mel Gorman <mel@....ul.ie>,
	Minchan Kim <minchan.kim@...il.com>,
	Rik van Riel <riel@...hat.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Lee Schermerhorn <lee.schermerhorn@...com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [patch] mm: disable user interface to manually rescue
 unevictable pages

On Tue, 27 Sep 2011 09:27:14 +0200
Johannes Weiner <jweiner@...hat.com> wrote:

> At one point, anonymous pages were supposed to go on the unevictable
> list when no swap space was configured, and the idea was to manually
> rescue those pages after adding swap and making them evictable again.
> But nowadays, swap-backed pages on the anon LRU list are not scanned
> without available swap space anyway, so there is no point in moving
> them to a separate list anymore.
> 
> The manual rescue could also be used in case pages were stranded on
> the unevictable list due to race conditions.  But the code has been
> around for a while now and newly discovered bugs should be properly
> reported and dealt with instead of relying on such a manual fixup.
> 
> In addition to the lack of a usecase, the sysfs interface to rescue
> pages from a specific NUMA node has been broken since its
> introduction, so it's unlikely that anybody ever relied on that.
> 
> This patch removes the functionality behind the sysctl and the
> node-interface and emits a one-time warning when somebody tries to
> access either of them.
> 
> Signed-off-by: Johannes Weiner <jweiner@...hat.com>
> Reported-by: Kautuk Consul <consul.kautuk@...il.com>

Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>

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