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Re: Gradual increase in CPU utilization by postmaster

From: "Yasuo Ohgaki" <yasuo_ohgaki(at)hotmail(dot)com>
To: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: <pgsql-admin(at)postgresql(dot)org>
Subject: Re: Gradual increase in CPU utilization by postmaster
Date: 2001-06-22 02:31:08
Message-ID: OE67bb1Say67xbHjkHX0000bfea@hotmail.com (view raw or flat)
Thread:
Lists: pgsql-admin
> "Yasuo Ohgaki" <yasuo_ohgaki(at)hotmail(dot)com> writes:
> > Postmaster size and CPU time increases gradually as time passes.
> > After 25 minutes elapsed, postmaster size became about 7000.
> > CPU time increased to about 90% from 70%.
> 
> > Terminating script and executing again will result in the same higher
> > CPU and memory usage.
> > Vacuuming table seems to reset this behavior.
> 
> Wait a minute, are we talking about *postmaster* size or *backend* size?
> 
> regards, tom lane

Sorry for the ambiguous description. It's *backend* size.
CPU usage and Memory size of the backend process continuously 
grows.  When I start the script, most of CPU time is used by 
system, and user time increases gradually.
Once CPU and Memory usage is increased, new backend, that uses the
table, end up with using the increased amount of resources (CPU and 
memory). To reset this behavior, the table is needed to be vacuumed 
and all backends, which are using the table, are needed to be terminated.

Table is very simple and has only 1 record.
test_table.sql
--------
CREATE TABLE test_table (
key  text,
val  text);

INSERT INTO test_table
(key,val) VALUES
('abc', 'aaa');
---------

Script 
pgtest.sh
--------
#!/bin/sh
while ( true ) ; do
  echo "UPDATE test_table SET val='xyz' where key='abc'; "
done
---------
% psql -f test_table.sql
% pgtest.sh | psql -q

Hope this helps.

Regards,
--
Yasuo Ohgaki

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