From: Greg Smith <gsmith@gregsmith.com>
To: Damon Hart <dhcom@sundial.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: PostgreSQL performance on various distribution stock kernels
Date: Mon, 26 Nov 2007 19:57:20 -0500 (EST)
Message-ID: <Pine.GSO.4.64.0711261937190.20455@westnet.com> (raw)
In-Reply-To: <1196117408.19996.16.camel@xw1.bbd>
References: <1196117408.19996.16.camel@xw1.bbd>
On Mon, 26 Nov 2007, Damon Hart wrote:
> Fedora 8:
> Linux 2.6.23.1-49.fc8 #1 SMP Thu Nov 8 21:41:26 EST 2007 i686 i686 i386
> GNU/Linux
>
> OpenVZ:
> Linux 2.6.18-8.1.15.el5.028stab049.1 #1 SMP Thu Nov 8 16:23:12 MSK 2007
> i686 i686 i386 GNU/Linux
2.6.23 introduced a whole new scheduler:
http://www.linux-watch.com/news/NS2939816251.html
so it's rather different from earlier 2.6 releases, and so new that there
could easily be performance bugs.
> Does your 10K RPM drive 166 TPS ceiling apply in this arrangement with
> multiple disks
Number of disks has nothing to do with it; it depends only on the rate the
disk with the WAL volume is spinning at. But that's for a single client.
> pgbench
> scale: 50
> clients: 50
> transactions per client: 100
With this many clients, you can get far more transactions per second
committed than the max for a single client (166@10K rpm). What you're
seeing, somewhere around 500 per second, is reasonable.
Note that you're doing two things that make pgbench less useful than it
can be:
1) The number of transactions you're committing is trivial, which is one
reason why your test runs have such a huge variation. Try 10000
transactions/client if you want something that doesn't vary quite so much.
If it doesn't run for a couple of minutes, you're not going to get good
repeatability.
2) The way pgbench works, it takes a considerable amount of resources to
simulate this many clients. You might get higher (and more realistic)
numbers if you run the pgbench client on another system than the server.
--
* Greg Smith gsmith@gregsmith.com http://www.gregsmith.com Baltimore, MD
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To: pgsql-performance@postgresql.org
Cc: gsmith@gregsmith.com, dhcom@sundial.com
Subject: Re: PostgreSQL performance on various distribution stock kernels
In-Reply-To: <Pine.GSO.4.64.0711261937190.20455@westnet.com>
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