Skip site navigation (1) Skip section navigation (2)

Re: Poor performance on seq scan

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Laszlo Nagy <gandalf(at)designaproduct(dot)biz>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Poor performance on seq scan
Date: 2006-09-12 20:48:57
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
Laszlo Nagy <gandalf(at)designaproduct(dot)biz> writes:
> Tom Lane wrote:
>> Why is that showing 85+ percent *system* CPU time??

> I'm sorry, this was really confusing. I don't know what it was - 
> probably a background system process, started from cron (?). I retried 
> the same query and I got this:
> [ around 80% idle CPU, 10% system, < 10% user ]

OK, so then the thing really is I/O bound, and Luke is barking up the
right tree.  The system CPU percentage still seems high though.
I wonder if there is a software aspect to your I/O speed woes ...
could the thing be doing PIO instead of DMA for instance?

			regards, tom lane

In response to

pgsql-performance by date

Next:From: Mischa SandbergDate: 2006-09-12 20:59:56
Subject: Bad plan for join to aggregate of join.
Previous:From: jallgoodDate: 2006-09-12 19:33:08

Privacy Policy | About PostgreSQL
Copyright © 1996-2017 The PostgreSQL Global Development Group