Re: poor cpu utilization on dual cpu box - Mailing list pgsql-performance

From Josh Berkus
Subject Re: poor cpu utilization on dual cpu box
Date
Msg-id 200310220911.14853.josh@agliodbs.com
Whole thread Raw
In response to poor cpu utilization on dual cpu box  (Simon Sadedin <pg_sicko@yahoo.com>)
Responses Re: poor cpu utilization on dual cpu box  (Tom Lane <tgl@sss.pgh.pa.us>)
Re: poor cpu utilization on dual cpu box  (Simon Sadedin <pg_sicko@yahoo.com>)
List 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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