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Re: Log levels for checkpoint/bgwriter monitoring

From: Greg Smith <gsmith(at)gregsmith(dot)com>
To: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Log levels for checkpoint/bgwriter monitoring
Date: 2007-03-07 04:14:37
Message-ID: Pine.GSO.4.64.0703062304230.24241@westnet.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Tue, 6 Mar 2007, Jim Nasby wrote:

> The flipside is that it's much easier to machine-parse a table rather 
> than trying to scrape the logs.

Now you might realize why I've been so vocal on the SQL log export 
implementation details.

> And I don't think we'll generally care about each individual checkpoint; 
> rather we'll want to look at things like 'checkpoints/hour' and 
> 'checkpoint written pages/hour'.

After a few months of staring at this data, I've found averages like that 
misleading.  The real problem areas correlate with the peak pages written 
at any one checkpoint.  Lowering that value is really the end-game for 
optimizing the background writer, and the peaks are what will nail you 
with a nasty fsync pause at checkpoint time.

--
* Greg Smith gsmith(at)gregsmith(dot)com http://www.gregsmith.com Baltimore, MD

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