On Mon, 14 Apr 2008, Gaetano Mendola wrote:
> I'm using postgres 8.2.3 on Red Hat compiled with GCC 3.4.6.
8.2.3 has a performance bug that impacts how accurate pgbench results are;
you really should be using a later version.
> as you can see using 64MB as value for shared_buffers I'm obtaining
> better results.
I'm assuming you've read my scaling article at
since you're using the graph template I suggest there.
If you look carefully at your results, you are getting better results for
higher shared_buffers values in the cases where performance is memory
bound (the lower scale numbers). Things reverse so that more buffers
gives worse performance only when your scale >100. I wouldn't conclude
too much from that. The pgbench select test is doing a low-level
operation that doesn't benefit as much from having more memory available
to PostgreSQL instead of the OS as a real-world workload will.
* Greg Smith gsmith(at)gregsmith(dot)com http://www.gregsmith.com Baltimore, MD
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