linux-kernel - Re: [PATCH] vmscan: evict use-once pages first (v2)

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Date:	Fri, 01 May 2009 16:05:55 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	elladan@...imo.com, peterz@...radead.org,
	linux-kernel@...r.kernel.org, tytso@....edu,
	kosaki.motohiro@...fujitsu.com, linux-mm@...ck.org
Subject: Re: [PATCH] vmscan: evict use-once pages first (v2)

Andrew Morton wrote:
> On Fri, 01 May 2009 10:05:53 -0400
> Rik van Riel <riel@...hat.com> wrote:

>> This means we need to provide our working set protection
>> on a per-list basis, by tweaking the scan rate or avoiding
>> scanning of the active file list alltogether under certain
>> conditions.
>>
>> As a side effect, this will help protect frequently accessed
>> file pages (good for ftp and nfs servers), indirect blocks,
>> inode buffers and other frequently used metadata.
> 
> Yeah, but that's all internal-implementation-of-the-day details.  It
> just doesn't matter how the sausages are made.  What we have learned is
> that the policy of retaining mapped pages over unmapped pages, *all
> other things being equal* leads to a more pleasing system.

Well, retaining mapped pages is one of the implementations
that lead to a more pleasing system.

I suspect that a fully scan resistant active file list will
show the same behaviour, as well as a few other desired
behaviours that come in very handy in various server loads.

Are you open to evaluating other methods that could lead, on
desktop systems, to a behaviour similar to the one achieved
by the preserve-mapped-pages mechanism?

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