linux-kernel - Re: [PATCH] vmscan: evict use-once pages first (v3)

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Message-ID: <20090430081029.GA23231@cmpxchg.org>
Date:	Thu, 30 Apr 2009 10:10:29 +0200
From:	Johannes Weiner <hannes@...xchg.org>
To:	Rik van Riel <riel@...hat.com>
Cc:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Elladan <elladan@...imo.com>, linux-kernel@...r.kernel.org,
	tytso@....edu, linux-mm@...ck.org
Subject: Re: [PATCH] vmscan: evict use-once pages first (v3)

On Wed, Apr 29, 2009 at 01:14:36PM -0400, Rik van Riel wrote:
> When the file LRU lists are dominated by streaming IO pages,
> evict those pages first, before considering evicting other
> pages.
> 
> This should be safe from deadlocks or performance problems
> because only three things can happen to an inactive file page:
> 1) referenced twice and promoted to the active list
> 2) evicted by the pageout code
> 3) under IO, after which it will get evicted or promoted
> 
> The pages freed in this way can either be reused for streaming
> IO, or allocated for something else. If the pages are used for
> streaming IO, this pageout pattern continues. Otherwise, we will
> fall back to the normal pageout pattern.
> 
> Signed-off-by: Rik van Riel <riel@...hat.com>

Although Elladan didn't test this exact patch, he reported on v2 that
the general idea of scanning active files only when they exceed the
inactive set works.

Acked-by: Johannes Weiner <hannes@...xchg.org>
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