Re: [PATCH] Use optimized single-datum tuplesort in ExecSort

Em qua., 14 de jul. de 2021 às 22:22, David Rowley <dgrowleyml(at)gmail(dot)com>
escreveu:

> On Thu, 15 Jul 2021 at 12:30, Ranier Vilela <ranier(dot)vf(at)gmail(dot)com> wrote:
> >
> > Em qua., 14 de jul. de 2021 às 21:21, David Rowley <dgrowleyml(at)gmail(dot)com>
> escreveu:
> >> But, in v8 there is no additional branch, so no branch to mispredict.
> >> I don't really see how your explanation fits.
> >
> > In v8 the branch occurs at :
> > + if (ExecGetResultType(outerPlanState(sortstate))->natts == 1)
>
> You do know that branch is in a function that's only executed once
> during executor initialization, right?
>
The branch prediction should work better.
I have no idea why it works worse.

I redid all tests:
notebook 8GB RAM 256GB SSD
ubuntu 64 bits (20.04)
clang-12
powerhigh (charger on)
none configuration (all defaults)

HEAD v6 v7b v8 v6
vs head
v7b vs v6 v8 vs v7b
Test1 576,868013 940,947236 1090,253859 1016,0443 163,11% 115,87% 93,19%
Test2 184,748363 177,6254 177,346229 178,230258 96,14% 99,84% 100,50%
Test3 410,030055 541,889704 605,843924 534,946166 132,16% 111,80% 88,30%
Test4 153,331752 147,98418 148,010894 147,771155 96,51% 100,02% 99,84%
Test5 268,97555 301,979647 316,928492 300,94932 112,27% 104,95% 94,96%
Test6 234,910125 259,71483 269,851427 260,567637 110,56% 103,90% 96,56%
Test7 142,704153 136,09163 136,802695 136,935709 95,37% 100,52% 100,10%
Test8 498,634855 763,482151 867,350046 804,833884 153,11% 113,60% 92,79%

The values are high here, because now, the tests are made with full power
of cpu to all patchs!
I think that more testing is needed with v7b and v8.

Anyway, two functions (ExecSortTuple and ExecSortDatum) are almost equal,
maybe not a good idea.

file results attached.

regards,
Ranier Vilela