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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>, "Rangachari Anand" <anand(at)reefedge(dot)com>
Cc: <pgsql-admin(at)postgresql(dot)org>
Subject: Re: Gradual increase in CPU utilization by postmaster
Date: 2001-06-21 06:22:56
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-admin
> "Rangachari Anand" <anand(at)reefedge(dot)com> writes:
> > We are running Postgres 7.0.3 on a Linux machine with a 2.4.0 kernel.
> > We have noticed that as we run our application which does
> > a lot of updates that CPU utilization (by postmaster) gradually
> > increases as time passes.
> Try 7.1.2 --- if it still does it in current sources, it'd be worth
> investigating further.  I recall a couple of bugs fixed that might
> explain this.
> regards, tom lane


It happened on my test system also
 - RedHat Linux 7.0.1 (kernel-2.2.19, glibc-2.2, gcc-2.96, 
    Intel Celeron466Mhz)
 - PostgreSQL 7.1.2 (build from src)

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. 

I've used the same script as Anand, but I think this situation is 
common in HTTP session management. (Updating the same record 
again and again.) Session record would not be updated as this test 
case, though. 

It seems I'm better off vacuuming my session table more often.

Hope this helps,
Yasuo Ohgaki

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