From: | Greg Smith <gsmith(at)gregsmith(dot)com> |
---|---|
To: | Rauan Maemirov <rauan(at)maemirov(dot)com> |
Cc: | pgsql-performance(at)postgresql(dot)org |
Subject: | Re: PostgreSQL 8.4 performance tuning questions |
Date: | 2009-07-31 04:10:40 |
Message-ID: | alpine.GSO.2.01.0907310002070.7409@westnet.com |
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Lists: | pgsql-performance |
On Thu, 30 Jul 2009, Rauan Maemirov wrote:
> maintenance_work_mem = 1GB
> work_mem = 192MB
> shared_buffers = 7680MB
> max_connections = 80
> My box is Nehalem 2xQuad 2.8 with RAM 32Gb
While it looks like you sorted out your issue downthread, I wanted to
point out that your setting for work_mem could be dangerously high here
and contribute to problems with running out memory or using swap. If each
of your 80 clients was doing a sort at the same time, you'd be using 80 *
192MB + 7680MB = 15360GB of RAM just for the server. The problem is that
each client could do multiple sorts, so usage might even got higher.
Unless you have a big data warehouse setup, more common work_mem settings
are in the 16-64MB range rather than going this high. Just something to
keep an eye on if you find a lot of memory is being used by the database
processes. I really need to refine the pgtune model to more carefully
account for this particular problem, it's a bit too aggressive here for
people who aren't proactively watching the server's RAM after changing the
settings.
--
* Greg Smith gsmith(at)gregsmith(dot)com http://www.gregsmith.com Baltimore, MD
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