Message-ID: <4CD46FFC.9060504@2ndquadrant.com>
Date: Fri, 05 Nov 2010 13:58:36 -0700
From: Greg Smith <greg@2ndquadrant.com>
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To: Mladen Gogala <mladen.gogala@vmsinfo.com>
CC: "pgsql-performance@postgresql.org" <pgsql-performance@postgresql.org>
Subject: Re: Bufer cache replacement LRU algorithm?
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Mladen Gogala wrote:
> Where can I find the documentation describing the buffer replacement 
> policy? Are there any parameters governing the page replacement policy?

I wrote a pretty detailed description of this in my "Inside the 
PostgreSQL Buffer Cache" presentation at 
http://projects.2ndquadrant.com/talks and nothing in this specific area 
has changed significantly since then.  There aren't any specific 
tunables in this area beyond the ones that cover sizing of the buffer 
pool and how often checkpoints happen.  There's a TODO item to benchmark 
toward whether there's any gain to increasing the maximum usage count an 
individual page can accumulate, currently hard coded at 5.  That's the 
main thing that could be tunable in this area that currently isn't.

-- 
Greg Smith   2ndQuadrant US    greg@2ndQuadrant.com   Baltimore, MD
PostgreSQL Training, Services and Support        www.2ndQuadrant.us
"PostgreSQL 9.0 High Performance": http://www.2ndQuadrant.com/books