Re: define pg_structiszero(addr, s, r)

On Fri, 1 Nov 2024 at 20:49, Michael Paquier <michael(at)paquier(dot)xyz> wrote:
>
> On Fri, Nov 01, 2024 at 07:44:22AM +0000, Bertrand Drouvot wrote:
> > Worth to add a comment as to why pg_memory_is_all_zeros() should not
> > be used here?
>
> I would not add one in bufpage.c, documenting that where
> pg_memory_is_all_zeros() is defined may be more adapted.

The thought of having to write a comment to warn people not to use it
for performance-critical things makes me think it might be better just
to write a more optimal version of the function so we don't need to
warn people. I looked around at the callers of the function I saw the
following numbers of bytes being used for the length: 8192 (the one in
question), 88, 32 and 112.

I don't know how performance-critical the final three of those are,
but I imagine all apart from the 32-byte one might be better with a
non-inlined and more optimised version of the function. The problem
with inlining the optimised version is that it's more code to inline.

I've attached what I thought a more optimal version might look like in
case anyone thinks making it better is a good idea.

David