Re: Move PinBuffer and UnpinBuffer to atomics

On Sun, Apr 17, 2016 at 7:32 PM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
wrote:

> On Thu, Apr 14, 2016 at 8:05 AM, Andres Freund <andres(at)anarazel(dot)de> wrote:
> >
> > On 2016-04-14 07:59:07 +0530, Amit Kapila wrote:
> > > What you want to see by prewarming?
> >
> > Prewarming appears to greatly reduce the per-run variance on that
> > machine, making it a lot easier to get meaningful results.
> >
>
> I think you are referring the tests done by Robert on power-8 m/c, but the
> performance results I have reported were on intel x86. In last two days, I
> have spent quite some effort to do the performance testing of this patch
> with pre-warming by using the same query [1] as used by Robert in his
> tests. The tests are done such that first it start server, pre-warms the
> relations, ran read-only test, stop server, again repeat this for next test.
>

What did you include into single run: test of single version (HEAD or
Patch) or test of both of them?

> I have observed that the variance in run-to-run performance still occurs
> especially at higher client count (128). Below are results for 128 client
> count both when the tests ran first with patch and then with HEAD and vice
> versa.
>
> Test-1
> ----------
> client count - 128 (basically -c 128 -j 128)
>
> first tests ran with patch and then with HEAD
>
> Patch_ver/Runs HEAD (commit -70715e6a) Patch
> Run-1 156748 174640
> Run-2 151352 150115
> Run-3 177940 165269
>
>
> Test-2
> ----------
> client count - 128 (basically -c 128 -j 128)
>
> first tests ran with HEAD and then with patch
>
> Patch_ver/Runs HEAD (commit -70715e6a) Patch
> Run-1 173063 151282
> Run-2 173187 140676
> Run-3 177046 166726
>
> I think this patch (padding pgxact) certainly is beneficial as reported
> above thread. At very high client count some variation in performance is
> observed with and without patch, but I feel in general it is a win.
>

So, what hardware did you use for these tests: power-8 or x86? How long was
single run?
Per-run variation seems quite high. It also seems that it depends on which
version runs first. But that could be a coincidence.

------
Alexander Korotkov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company