Date: Tue, 14 Oct 2008 10:02:26 -0400 (EDT)
From: Greg Smith <gsmith@gregsmith.com>
To: =?ISO-8859-1?Q?Mikkel_H=F8gh?= <mikkel@hoegh.org>
cc: pgsql-general@postgresql.org
Subject: Re: Drupal and PostgreSQL - performance issues?
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On Tue, 14 Oct 2008, Mikkel H=F8gh wrote:

> You are targetting DBAs using servers with less than 512 MB RAM. Is=20
> PostgreSQL supposed to be used by professional DBAs on enterprise=20
> systems or is it supposed to run out of the box on my old Pentium 3?

Take a look at http://bugzilla.kernel.org/show_bug.cgi?id=3D11381

There you'll discover that the Linux default for how much memory an=20
application like PostgreSQL can allocate is 32MB.  This is true even if=20
you install the OS on a system with 128GB of RAM.  If PostgreSQL created a=
=20
default configuration optimized for "enterprise systems", that=20
configuration wouldn't even start on *any* Linux system with the default=20
kernel settings.  The above is an attempt to change that, rejected with=20
the following text that aptly describes the default PostgreSQL=20
configuration as well:  "The requirement is that SHMMAX is sane for the=20
user by default and that means *safe* rather than as big as possible".=20
The situation on most other operating systems is similarly bad.

So the dichotomy here is even worse than you think:  it's not just that=20
the performance profile would be wrong, it's that defaults targeting=20
modern hardware would make it so the database won't even start on your old=
=20
Pentium 3.  The best the PostgreSQL community can do is provide=20
documentation on how you re-tune your *operating system first*, then the=20
database server, to get good performance on systems with modern amounts of=
=20
RAM.

Admittedly, that documentation and related support tools should be better,=
=20
mainly by being easier to find.  This discussion is well timed in that I=20
was planning this month to propose adding a URL with a tuning guide and/or=
=20
sample configurations to the top of the postgresql.conf file before the=20
next release comes out; when that comes up I can point to this thread as a=
=20
reminder of why that's needed.

--
* Greg Smith gsmith@gregsmith.com http://www.gregsmith.com Baltimore, MD=