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postgres: 100% CPU utilization

From: "Sergey Tsukinovsky" <Sergey(dot)Tsukinovsky(at)cryptologic(dot)com>
To: <pgsql-performance(at)postgresql(dot)org>
Subject: postgres: 100% CPU utilization
Date: 2007-04-19 19:29:52
Message-ID: 2C20E65455FC964690D89F8C4A2E9B1D03A669CD@STRAIGHTFLUSH.cryptologic.com (view raw or flat)
Thread:
Lists: pgsql-performance
Hi,

 

I'm currently dealing with performance issues of postgres and looking
for some advice.

 

Platform

Postgres: 7.0.2

OS: FreeBSD4.4

DB: size - about 50M, most frequently updated tables are of an average
size of 1000-2000 rows and there are not many of them, about 15 in total

 

Description

My current system load keeps the postgres CPU utilization at the level
of 90-100%. 

'vacuumdb' results in a sharp drop of the CPU usage down to 25-30%, but
not for a long period of time - it gets back to 100% within 30 minutes.

Disk IO ratio during the test keeps on about 0.5 MB/s

 

Questions:

1. When reading the 'vacuum analyze' output how to identify which one of
the actions had the most effect on reducing the CPU usage - garbage
cleaning or statistics recalculation for the analyzer?

2. What would be the recommended set of parameters to tune up in order
to improve the performance over the time, instead of considering an
option to vacuum every 30 minutes or so?

3. Is it safe to run 'vacuum' as frequently as every 15-30 minutes?

4. Suggestions?

 

I know that 7.0.2 is an old version and therefore ran the same test on
7.3.18 - the performance behavior was similar. 

 

Thank you in advance,

Sergey

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