Re: Postgres Config/Tuning problem

"Andrew Walmsley" <andrew.walmsley@ttsltd.com> writes:
> We have what I would call a beast of a machine, 8 * 2.7 GHz Xeon
> processors, with 4 GB of memory, running Red Hat Enterprise (
> 2.6.9-11.ELsmp ) and PostgreSql  7.4.8
> ...
> The processors are all showing 80-95% idle, but vmstat shows 20,000+
> context switches and is dropping processes from the run queue.=20

This sounds a lot like the buffer contention problems that we fixed in
PG 8.1.

However, it might be something simpler than that.  Are you vacuuming the
updated table(s) on a regular basis?  It sounds like your update process
might involve replacing the entire table contents, in which case you'd
really better vacuum after each such update.

> shared_buffers = 128000         # min 16, at least max_connections*2,

On 7.4 I'd cut that down by a factor of 10, unless you've specifically
measured that the higher number is better for your workload.  7.4 does
not have amazingly good buffer management behavior.

> #max_fsm_pages = 20000          # min max_fsm_relations*16, 6 bytes =

You didn't say much about the total size of your database, but for
almost any production situation, this default is too small.

            regards, tom lane