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Serious issues with CPU usage

From: <andris(at)neti(dot)ee>
To: <pgsql-performance(at)postgresql(dot)org>
Subject: Serious issues with CPU usage
Date: 2003-09-05 21:58:29
Message-ID: 20030905215635.68C1173595@MX2.estpak.ee (view raw or flat)
Thread:
Lists: pgsql-performance
Hi,

i'm having _serious_ issues of postgres hogging up the CPU over time. A graph
showing this can be seen at http://andri.estpak.ee/cpu0.png .

The database is running on Redhat 9 (stock 2.4.20-8 kernel), on a reiserfs
partition (~8% usage - no problem there), and this problem has been with
PostgreSQL 7.3.2 (both package provided by Redhat and self-rebuilt package)
and 7.3.4 (i used the 7.3.4 SRPM available at postgres ftp site).

A VACUUM FULL is a remedy to this problem, but a simple VACUUM isn't. 

This can be reproduced, I think, by a simple UPDATE command:

database=# EXPLAIN ANALYZE UPDATE table SET random_int_field = 1, last_updated
= NOW() WHERE primary_key = 3772;
                                                           QUERY PLAN
---------------------------------------------------------------------------------------------------------------------------------
 Index Scan using table_pkey on table  (cost=0.00..6.81 rows=1 width=83)
(actual time=0.09..0.10 rows=1 loops=1)
   Index Cond: (primary_key = 3772)
 Total runtime: 0.37 msec

When I repeat this command using simple <up><enter>, I can see the "Total
runtime" time grow ever so slightly - creeping from 0.37 to 0.38, then 0.39
etc.   Would probably get higher if I had the patience. :)

The table "table" used in this example has 2721 rows, so size isn't an issue here.

Any comments or suggestions are welcome. If more information is needed, let me
know and I'll post the needed details.

Responses

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Next:From: Tom LaneDate: 2003-09-06 00:05:00
Subject: Re: Serious issues with CPU usage
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Subject: Re: [PERFORM] Seq scan of table?

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