Re: Quantify small changes to predicate evaluation

On Tue, Jun 17, 2014 at 5:23 PM, Dennis Butterstein <soullinuxer(at)web(dot)de> wrote:
> I tried the proposed tweaks and
> see some differences regarding the measurements.
> Unfortunately the variance between the runs seems to remain high.

Using these techniques I managed to get standard deviation below 1.5%
in my read-only tests (and most below 1%). Not all workloads may be
able to achieve that, but your should be able to do better than your
results.

Maybe your cooling is not sufficient? It seems your 2nd run is always
slower than the first one, maybe the CPU is doing thermal throttling?
Lowering the max frequency might be something to try to resolve that,
like "cpupower frequency-set --max 2GHz"

How do you run your benchmark, are you using pgbench? Single threaded?
Is the client locked to the same CPU core?

Regards,
Marti