Re: [Testperf-general] pg_autovacuum w/ dbt2

From: Josh Berkus <josh(at)agliodbs(dot)com>
To: testperf-general(at)pgfoundry(dot)org
Cc: Mark Wong <markw(at)osdl(dot)org>, "Matthew T(dot) O'Connor" <matthew(at)zeut(dot)net>, tgl(at)sss(dot)pgh(dot)pa(dot)us, pgsql-hackers(at)postgresql(dot)org
Subject: Re: [Testperf-general] pg_autovacuum w/ dbt2
Date: 2005-01-07 17:58:47
Message-ID: 200501070958.47834.josh@agliodbs.com
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Mark,

> No manual vacuum commands before. The decline in performance has been
> pretty consistent in all my previous tests and people have told me on
> many occasions that the decline in performance was probably because I
> was never using vacuum...

Hmmm ... what autovacuum params are you using? From the look of the graphs,
VACUUM is running every 6 minutes or so, and having a huge impact on
performance when it does run. Give me a bit of time to crunch the database
log, and we'll see which table vacuums were taking the most time.

Can you re-run this test with a fairly generous vacuum_delay setting? Given
that the performance drops seem to correspond to wait times, I think this
could mean a big difference.

--
Josh Berkus
Aglio Database Solutions
San Francisco

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