linux-kernel - Re: Increased Buffers due to patch 56e49d (vmscan: evict use-once pages first), but why exactly?

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Message-ID: <4B1E7B47.1000707@redhat.com>
Date:	Tue, 08 Dec 2009 11:13:59 -0500
From:	Rik van Riel <riel@...hat.com>
To:	Christian Ehrhardt <ehrhardt@...ux.vnet.ibm.com>
CC:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Elladan <elladan@...imo.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Lee Schermerhorn <lee.schermerhorn@...com>,
	Johannes Weiner <hannes@...xchg.org>,
	Andrew Morton <akpm@...ux-foundation.org>, epasch@...ibm.com,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>
Subject: Re: Increased Buffers due to patch 56e49d (vmscan: evict use-once
 pages first), but why exactly?

On 12/08/2009 10:54 AM, Christian Ehrhardt wrote:

> btw thanks for the explanation Rik, the file/blockdev association was
> exactly what I was missing in my thoughts.
> While my question was more intended to ask where in code these
> differentiation is made I'm perfectly fine with having it just working
> knowing that file/blockdev association is the key.

Actually, the file/blockdev association is just a coincidence,
due to the way your benchmark works.

The key is "page touched once" vs "page touched multiple times".

In eg. a database workload, I would expect much more file data
to be on the active list.  Specifically the file data corresponding
to the database indexes.

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