Date: Tue, 2 Apr 2013 18:36:09 +0200
From: Andres Freund <andres@2ndquadrant.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Robert Haas <robertmhaas@gmail.com>,
	Merlin Moncure <mmoncure@gmail.com>, Jim Nasby <jim@nasby.net>,
	Jeff Janes <jeff.janes@gmail.com>, Ants Aasma <ants@cybertec.at>,
	Atri Sharma <atri.jiit@gmail.com>, Greg Stark <stark@mit.edu>,
	Amit Kapila <amit.kapila@huawei.com>,
	PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: Page replacement algorithm in buffer cache
Message-ID: <20130402163609.GG2415@alap2.anarazel.de>
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On 2013-04-02 12:22:03 -0400, Tom Lane wrote:
> Robert Haas <robertmhaas@gmail.com> writes:
> > But, having said that, I still think the best idea is what Andres
> > proposed, which pretty much matches my own thoughts: the bgwriter
> > needs to populate the free list, so that buffer allocations don't have
> > to wait for linear scans of the buffer array.  That's just plain too
> > slow.
> 
> I agree in general, though I'm not sure the bgwriter process can
> reasonably handle this need along with what it's already supposed to be
> doing.  We may need another background process that is just responsible
> for keeping the freelist populated.

What else is the bgwriter actually doing otherwise? Sure, it doesn't put the
pages on the freelist, but otherwise its trying to do the above isn't it?

Greetings,

Andres Freund

-- 
 Andres Freund	                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services


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