Re: Speed up Clog Access by increasing CLOG buffers

On Thu, Mar 24, 2016 at 8:08 AM, Amit Kapila <amit.kapila16@gmail.com> wrote:
>
> On Thu, Mar 24, 2016 at 5:40 AM, Andres Freund <andres@anarazel.de> wrote:
> >
> > Have you, in your evaluation of the performance of this patch, done
> > profiles over time? I.e. whether the performance benefits are the
> > immediately, or only after a significant amount of test time? Comparing
> > TPS over time, for both patched/unpatched looks relevant.
> >
>
> I have mainly done it with half-hour read-write tests. What do you want to observe via smaller tests, sometimes it gives inconsistent data for read-write tests?
>

I have done some tests on both intel and power m/c (configuration of which are mentioned at end-of-mail) to see the results at different time-intervals and it is always showing greater than 50% improvement in power m/c at 128 client-count and greater than 29% improvement in Intel m/c at 88 client-count.

Client-count - 128

Time (minutes)	Base	Patch	%
5	42479	65655	54.55
10	41876	66050	57.72
20	38099	65200	71.13
30	37838	61908	63.61

 

>
> >
> > Even after changing to scale 500, the performance benefits on this,
> > older 2 socket, machine were minor; even though contention on the
> > ClogControlLock was the second most severe (after ProcArrayLock).
> >
>
> I have tried this patch on mainly 8 socket machine with 300 & 1000 scale factor.  I am hoping that you have tried this test on unlogged tables and by the way at what client count, you have seen these results.
>

Do you think in your tests, we don't see increase in performance in your tests because of m/c difference (sockets/cpu cores) or client-count?