On Mon, Oct 04, 2004 at 02:42:43PM -0400, Greg Stark wrote:
> Mark Wong <markw@osdl.org> writes:
>
> > Links to results are here:
> > 7.5devel - http://www.osdl.org/projects/dbt2dev/results/dev4-010/128/
> > 8.0beta3 - http://www.osdl.org/projects/dbt2dev/results/dev4-010/180/
>
> Are those cyclic spikes an artifact of the load of the tests? Or are they
> artifacts of the postgres checkpoint process?
>
> If they're an artifact of the test is it possible to randomize the number
> iterations and time each connection does before issuing the slower queries? Or
> somehow avoid generating these spikes?
>
> If they're an artifact of the checkpoint process I wonder if there are
> parameters that can be tweaked to smooth it out more. Some of those
> transactions/second drops are quite dramatic. It seems like you're averaging
> 200 txn/s normally but having it drop down to less than half that
> periodically.
>
In the past, they have been artifacts of the checkpoint process. They
do smooth out as I increase the checkpoint segments and the timeout.
Although I know that doesn't exactly exclude other explanations.
There are 5000 emulated clients connected through 100 database connections
for both of those tests, attempting 1 of 5 different transactions. I hope
that's random enough. :)
When I run a less intense workload, everything smooths out a bit more too
but it doesn't stress the system nearly as much.
Mark