From: Greg Smith <greg@2ndQuadrant.com>
To: Costin Oproiu <costin.oproiu@gmail.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: pgbench intriguing results: better tps figures for larger scale factor
Date: Mon, 04 Mar 2013 17:46:29 -0500
Message-ID: <51352445.4050305@2ndQuadrant.com> (raw)
In-Reply-To: <CAEmewRLOADSHk4A5EmYrT8puZ7zFxw8H6bQEJ2_BVPkdFTikSA@mail.gmail.com>
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On 2/26/13 4:45 PM, Costin Oproiu wrote:
> First, I've got no good explanation for this and it would be nice to
> have one. As far as I can understand this issue, the heaviest update
> traffic should be on the branches table and should affect all tests.
From http://www.postgresql.org/docs/current/static/pgbench.html :
"For the default TPC-B-like test scenario, the initialization scale
factor (-s) should be at least as large as the largest number of clients
you intend to test (-c); else you'll mostly be measuring update
contention. There are only -s rows in the pgbench_branches table, and
every transaction wants to update one of them, so -c values in excess of
-s will undoubtedly result in lots of transactions blocked waiting for
other transactions."
I normally see peak TPS at a scale of around 100 on current generation
hardware, stuff in the 4 to 24 core range. Nowadays there really is no
reason to consider running pgbench on a system with a smaller scale than
that. I normally get a rough idea of things by running with scales 100,
250, 500, 1000, 2000.
--
Greg Smith 2ndQuadrant US greg@2ndQuadrant.com Baltimore, MD
PostgreSQL Training, Services, and 24x7 Support www.2ndQuadrant.com
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To: pgsql-performance@postgresql.org
Cc: greg@2ndQuadrant.com, costin.oproiu@gmail.com
Subject: Re: pgbench intriguing results: better tps figures for larger scale factor
In-Reply-To: <51352445.4050305@2ndQuadrant.com>
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