| From: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
|---|---|
| To: | Dimitri <dimitrik(dot)fr(at)gmail(dot)com> |
| Cc: | Dimitri Fontaine <dfontaine(at)hi-media(dot)com>, Alvaro Herrera <alvherre(at)commandprompt(dot)com>, Aidan Van Dyk <aidan(at)highrise(dot)ca>, Merlin Moncure <mmoncure(at)gmail(dot)com>, PostgreSQL Performance <pgsql-performance(at)postgresql(dot)org> |
| Subject: | Re: Any better plan for this query?.. |
| Date: | 2009-05-12 11:49:41 |
| Message-ID: | 1242128981.3843.257.camel@ebony.2ndQuadrant |
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| Lists: | pgsql-performance |
On Tue, 2009-05-12 at 12:19 +0200, Dimitri wrote:
> What I'm trying to do now is to understand what exactly is the
> problem.
You're running with 1600 users, which is above the scalability limit
uncovered (by Sun...) during earlier benchmarking. The scalability
issues are understood but currently considered above the
reasonable-setting limit and so nobody has been inclined to improve
matters.
You should use a connection concentrator to reduce the number of
sessions down to say 400.
You're WAL buffers setting is also too low and you will be experiencing
contention on the WALWriteLock. Increase wal_buffers to about x8 where
you have it now.
You can move pg_xlog to its own set of drives.
Set checkpoint_completion_target to 0.95.
--
Simon Riggs www.2ndQuadrant.com
PostgreSQL Training, Services and Support
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