> 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.
P.
