From: Chris Browne <cbbrowne@acm.org>
Subject: Re: Background writer underemphasized ...
Date: Wed, 16 Apr 2008 13:47:59 -0400
Organization: cbbrowne Computing Inc
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Message-ID: <60abjtu1ww.fsf@dba2.int.libertyrms.com>
References: <480619CA.2080904@geizhals.at>
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To: pgsql-performance@postgresql.org

mjy@geizhals.at (Marinos Yannikos) writes:
> This helped with our configuration:
> bgwriter_delay = 10000ms         # 10-10000ms between rounds
> bgwriter_lru_maxpages = 1000     # 0-1000 max buffers written/round

FYI, I'd be inclined to reduce both of those numbers, as it should
reduce the variability of behaviour.

Rather than cleaning 1K pages every 10s, I would rather clean 100
pages every 1s, as that will have much the same effect, but spread the
work more evenly.  Or perhaps 10 pages every 100ms...

Cut the delay *too* low and this might make the background writer, in
effect, poll *too* often, and start chewing resources, but there's
doubtless some "sweet spot" in between...
-- 
"cbbrowne","@","cbbrowne.com"
http://linuxdatabases.info/info/oses.html
"For systems, the analogue of a face-lift is to add to the control
graph an edge that creates a cycle, not just an additional node."
-- Alan J. Perlis