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Performance Issues on Opteron Dual Core

From: "Gregory Stewart" <gstewart(at)sweetdata(dot)com>
To: pgsql-performance(at)postgresql(dot)org
Subject: Performance Issues on Opteron Dual Core
Date: 2006-04-28 20:29:58
Message-ID: e2tts8$1c70$ (view raw, whole thread or download thread mbox)
Lists: pgsql-performance

We are currently developing a web application and have the webserver and 
PostgreSQL with our dev db running on a machine with these specs:

Win 2003 standard
AMD Athlon XP 3000 / 2.1 GHZ
2 Gig ram
120 gig SATA HD
PostgreSQL 8.1.0
Default pgsql configuration + shared buffers = 30,000

The performance of postgresql and our web application is good on that 
machine, but we decided to build a dedicated database server for our 
production database that scales better and that we can also use for internal 
applications (CRM and so on).

To make a long story short, we built a machine with these specs:

Windows 2003 Standard
AMD Opteron 165 Dual Core / running at 2 GHZ
2 gig ram
2 x 150 Gig SATA II HDs in RAID 1 mode (mirror)
PostgreSQL 8.1.3
Default pgsql configuration + shared buffers = 30,000

Perfomance tests in windows show that the new box outperforms our dev 
machine quite a bit in CPU, HD and memory performance.

I did some EXPLAIN ANALYZE tests on queries and the results were very good, 
3 to 4 times faster than our dev db.

However one thing is really throwing me off.
When I open a table with 320,000 rows / 16 fields in the pgadmin tool (v 
1.4.0) it takes about 6 seconds on the dev server to display the result (all 
rows). During these 6 seconds the CPU usage jumps to 90%-100%.

When I open the same table on the new, faster, better production box, it 
takes 28 seconds!?! During these 28 seconds the CPU usage jumps to 30% for 1 
second, and goes back to 0% for the remaining time while it is running the 

What is going wrong here? It is my understanding that postgresql supports 
multi-core / cpu environments out of the box, but to me it appears that it 
isn't utilizing any of the 2 cpu's available. I doubt that my server is that 
fast that it can perform this operation in idle mode.

I played around with the shared buffers and tried out versions 8.1.3, 8.1.2, 
8.1.0 with the same result.

Has anyone experienced this kind of behaviour before?
How representative is the query performance in pgadmin?

I appreciate your ideas, comments and help.



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Subject: Re: Why so slow?
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