Re: [HACKERS] Atomics for heap_parallelscan_nextpage()

Andres Freund <andres@anarazel.de> writes:
> Don't think we require BUFFERALIGN - MAXALIGN ought to be
> sufficient.

Uh, see my other message just now.

> The use of BUFFERALIGN presumably is to space out things
> into different cachelines, but that doesn't really seem to be important
> with this.  Then we can just avoid defining the new macro...

I was feeling a bit uncomfortable with the BUFFERALIGN_DOWN() for a
different reason: if the caller has specified the exact amount of space it
needs, having shm_toc_create discard some could lead to an unexpected
failure.  I wonder whether maybe shm_toc_create should just error out if
the number it's handed isn't aligned already.

>> +    return BUFFERALIGN(
>> +        add_size(offsetof(shm_toc, toc_entry),
>> +                 add_size(mul_size(e->number_of_keys, sizeof(shm_toc_entry)),
>> +                          e->space_for_chunks)));

> I think splitting this into separate statements would be better.

+1, it was too complicated already.
        regards, tom lane