Em dom., 18 de jul. de 2021 às 21:23, Peter Smith <smithpb2...@gmail.com> escreveu:
> > > On Sun, Jul 18, 2021 at 11:09 PM Ranier Vilela <ranier...@gmail.com> > wrote: > >> ... >> > I did the patch, but to my surprise, the results weren't so good. >> Despite that claiming a tiny improvement in performance, I didn't expect >> any slowdown. >> I put a counter in pg_regress.c, summing the results of each test and did >> it three times for HEAD and for the patch. >> Some tests were better, but others were bad. >> Tests comments per example, show 180%, combocid 174%, dbize 165%, xmlmap >> 136%, lock 134%. >> >> ... ... >> >> So I'm posting the patch here, merely as an illustration of my findings. >> Perhaps someone with a better understanding of the process of translating >> C to asm can have an explanation. >> Is it worth it to change only where there has been improvement? >> >> > My guess is that your hypothetical performance improvement has been > completely swamped by the natural variations of each run. > > For example, > drop_if_exists 115 84 83 94 > 138 63 57 86 109,30% > > Those numbers are all over the place, so I doubt the results are really > saying anything at all about what is better/worse, because I think you have > zero chance to notice a couple of nanoseconds of improvement within the > noise when each run is varying from 57 to 138 ms. > > IMO the only conclusion you can draw from your results is that any > performance gain is too small to be observable. > Thanks Peter for your explanations. I can conclude then that the test results are not a reference for performance/regression. So the patch serves as a refactoring, without any further indication. regards, Ranier Vilela
