linux-kernel - Re: [PATCH RFC] fadvise: move active pages to inactive list with POSIX_FADV

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Date:	Wed, 22 Jun 2011 19:04:28 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Andrea Righi <andrea@...terlinux.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Minchan Kim <minchan.kim@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Johannes Weiner <hannes@...xchg.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Hugh Dickins <hughd@...gle.com>,
	Jerry James <jamesjer@...terlinux.com>,
	Marcus Sorensen <marcus@...ehost.com>,
	Matt Heaton <matt@...ehost.com>, linux-mm <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC] fadvise: move active pages to inactive list with
 POSIX_FADV_DONTNEED

On 06/22/2011 05:51 PM, Andrea Righi wrote:
> There were some reported problems in the past about trashing page cache
> when a backup software (i.e., rsync) touches a huge amount of pages (see
> for example [1]).
>
> This problem has been almost fixed by the Minchan Kim's patch [2] and a
> proper use of fadvise() in the backup software. For example this patch
> set [3] has been proposed for inclusion in rsync.
>
> However, there can be still other similar trashing problems: when the
> backup software reads all the source files, some of them may be part of
> the actual working set of the system. When a
> posix_fadvise(POSIX_FADV_DONTNEED) is performed _all_ pages are evicted
> from pagecache, both the working set and the use-once pages touched only
> by the backup software.
>
> With the following solution when posix_fadvise(POSIX_FADV_DONTNEED) is
> called for an active page instead of removing it from the page cache it
> is added to the tail of the inactive list. Otherwise, if it's already in
> the inactive list the page is removed from the page cache.

> Signed-off-by: Andrea Righi<andrea@...terlinux.com>

Acked-by: Rik van Riel <riel@...hat.com>

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