Re: pgbench Comparison of 7.4.7 to 8.0.2

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Thomas F(dot)O'Connell" <tfo(at)sitening(dot)com>
Cc: PgSQL - Performance <pgsql-performance(at)postgresql(dot)org>
Subject: Re: pgbench Comparison of 7.4.7 to 8.0.2
Date: 2005-04-15 21:23:34
Message-ID: 6865.1113600214@sss.pgh.pa.us
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"Thomas F.O'Connell" <tfo(at)sitening(dot)com> writes:
> http://www.sitening.com/pgbench.html

You need to run *many* more transactions than that to get pgbench
numbers that aren't mostly noise. In my experience 1000 transactions
per client is a rock-bottom minimum to get repeatable numbers; 10000 per
is better.

Also, in any run where #clients >= scaling factor, what you're measuring
is primarily contention to update the "branches" rows. Which is not
necessarily a bad thing to check, but it's generally not the most
interesting performance domain (if your app is like that you need to
redesign the app...)

> To me, it looks like basic transactional performance is modestly
> improved at 8.0 across a variety of metrics.

That's what I would expect --- we usually do some performance work in
every release cycle, but there was not a huge amount of it for 8.0.

However, these numbers don't prove much either way.

regards, tom lane

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