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Re: 8.4 open item: copy performance regression?

From: Greg Smith <gsmith(at)gregsmith(dot)com>
To: Simon Riggs <simon(at)2ndQuadrant(dot)com>
Cc: Stefan Kaltenbrunner <stefan(at)kaltenbrunner(dot)cc>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Andrew Dunstan <andrew(at)dunslane(dot)net>, Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Alan Li <ali(at)truviso(dot)com>
Subject: Re: 8.4 open item: copy performance regression?
Date: 2009-06-21 06:45:04
Message-ID: alpine.GSO.2.01.0906210241020.7754@westnet.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Sat, 20 Jun 2009, Simon Riggs wrote:

> I would suggest that we check how much WAL has been written. There may
> be a secondary effect or a different regression hidden in these results.

What's the easiest way to do that?  My first thought was to issue a 
checkpoint before the test (which is a good idea to make each test 
consistent anyway), save the output from pg_controldata, test, checkpoint, 
and look at the control data again.  This seems kind of clunky though, but 
still better than trolling through the OS statistics for the data.  Any 
clever ideas for a better way to measure bytes of WAL written during a 
particular chunk of code?  We may need some sort of checkpoint/sync after 
the test to get correct results, because I've noticed that the tests I run 
sometimes continue writing out buffers for a few seconds after the test 
time is finished.

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

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Subject: Re: 8.4 open item: copy performance regression?
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