Re: tuning questions

>
> IO is active, but hardly saturated. CPU load is hefty though, load
> average is at 4 now.
>
>    procs                      memory    swap          io
> system         cpu
>  r  b  w   swpd   free   buff  cache  si  so    bi    bo   in    cs  
> us  sy  id

>  0  2  1   2808  11432  39616 1902984   0   0   204   876  788   507  
> 3   4  93

You're getting a load average of 4 with 93% idle?

That's a reasonable number of context switches, and if the blocks 
you're reading/writing are discontinous, I could see io saturation 
rearing it's head.

This looks to me like you're starting and killing a lot of processes.

Is this thrashing psql connections, or is it one big query? What are 
your active processes?

Your effective cache size looks to be about 1900 megs (+- binary), 
assuming all of it is pg.

eric