Ed L. wrote:

> Well, I think we clearly have an HPUX CPU bottleneck (long pri 
> queue, high cpu utilization, high user cpu %, lots of processes 
> "blocked on pri").
> 
> It seems to get worst and slow all queries down across the board 
> when autovac tries to vacuum a 15GB table.  I'm guessing this is 
> flushing the OS/DB caches, exacerbating the CPU bottleneck.
> 
> I'm also not sure what to do about it beyond the customer buying 
> some politically/financially expensive CPUs.

I suggest turning autovac off for that particular table, and doing the
vacuum during off-peak hours.

> The table in 
> question appears to be the pathological case for vacuum:  very 
> large with lots of frequent UPDATEs.  It's essentially a log 
> table.

A big log table where the log entries are being updated?  Certainly
sounds like a recipe for vacuum headaches.

-- 
Alvaro Herrera                                http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support

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