On 2019-04-09 10:12:56 -0700, Paul Ramsey wrote:
>
> > On Apr 9, 2019, at 10:09 AM, Andrey Borodin <x4...@yandex-team.ru> wrote:
> >
> > He advised me to use algorithm that splits copied regions into smaller
> > non-overlapping subregions with exponentially increasing size.
> >
> > while (off <= len)
> > {
> > memcpy(dp, dp - off, off);
> > len -= off;
> > dp += off;
> > off *= 2;
> > }
> > memcpy(dp, dp - off, len);
> >
> > On original Paul's test without patch of this thread this optimization gave
> > about x2.5 speedup.
> > I've composed more detailed tests[0] and tested against current master. Now
> > it only gives 20%-25% of decompression speedup, but I think it is still
> > useful.
>
> Wow, well beyond slicing, just being able to decompress 25% faster is a win
> for pretty much any TOAST use case. I guess the $100 question is:
> portability? The whole reason for the old-skool code that’s there now was
> concerns about memcpy’ing overlapping addresses and Bad Things happening.
Just use memmove? It's usually as fast these days.
