From: | Andres Freund <andres(at)anarazel(dot)de> |
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To: | Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr> |
Cc: | PostgreSQL Developers <pgsql-hackers(at)postgresql(dot)org>, Robert Haas <robertmhaas(at)gmail(dot)com> |
Subject: | Re: pgbench randomness initialization |
Date: | 2016-04-07 10:02:15 |
Message-ID: | 20160407100215.kl3e566z4y6v4nkj@alap3.anarazel.de |
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Lists: | pgsql-hackers |
On 2016-04-07 11:56:12 +0200, Fabien COELHO wrote:
> (2) runs which really vary from one to the next, so as
> to have an idea about how much it may vary, what is the
> performance stability.
I don't think this POV makes all that much sense. If you do something
non-comparable, then the results aren't, uh, comparable. Which also
means there's a lower chance to reproduce observed problems.
> Currently pgbench focusses on (2), which may or may not be fine depending on
> what you are doing. From a personal point of view I think that (2) is more
> significant to collect performance data, even if the results are more
> unstable: that simply reflects reality and its intrinsic variations, so I'm
> fine that as the default.
Uh, and what's the benefit of that variability? pgbench isn't a reality
simulation tool, it's a benchmarking tool. And benchmarks with intrisinc
variability are bad benchmarks.
Greetings,
Andres Freund
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