Re: Pgbench performance tuning?

On 2016-08-04 19:15:43 +0100, Greg Stark wrote:
> On Thu, Aug 4, 2016 at 6:53 PM, Andres Freund <andres@anarazel.de> wrote:
> > What's the config? Version? What activity does pidstat -d -l indicate?
> > How much WAL was generated?
> 
> I know the specifics matter but I was also trying to avoid dumping too
> much into the email.
> 
> The shared buffers is set to 16384 (128MB). Otherwise it's a default
> config (For 9.4 and before I set checkpoint_segments to 32 as well).

Well, with 128MB I don't find that a very surprising result. You're
going to push data out to disk constantly. Given the averaged random
access pattern of pgbench that's not really something that interesting.


> Never seen pidstat before but pidstat -d looks like it prints very
> similar output to the iostat output I was gathering already. There's
> nothing else running on the machine.

The question is which backends are doing the IO.


Greetings,

Andres Freund