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Re: poor cpu utilization on dual cpu box

From: Josh Berkus <josh(at)agliodbs(dot)com>
To: Simon Sadedin <pg_sicko(at)yahoo(dot)com>,pgsql-performance(at)postgresql(dot)org
Subject: Re: poor cpu utilization on dual cpu box
Date: 2003-10-22 16:11:14
Message-ID: 200310220911.14853.josh@agliodbs.com (view raw or flat)
Thread:
Lists: pgsql-performance
Simon,

> The issue is that no matter how much query load we throw at our server it
> seems almost impossible to get it to utilize more than 50% cpu on a
> dual-cpu box.  For a single connection we can use all of one CPU, but
> multiple connections fail to increase the overall utilization (although
> they do cause it to spread across CPUs).

This is perfectly normal.   It's a rare x86 machine (read fiber channel) where 
you don't saturate the I/O or the RAM *long* before you saturate the CPU.  
Transactional databases are an I/O intensive operation, not a CPU-intensive 
one.

>  We are running with shared buffers large enough to hold the
> entire database

Which is bad.   This is not what shared buffers are for.  See:
http://www.varlena.com/varlena/GeneralBits/Tidbits/perf.html

-- 
Josh Berkus
Aglio Database Solutions
San Francisco

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