Re: define pg_structiszero(addr, s, r)

David Rowley <dgrowleyml@gmail.com>

From: David Rowley <dgrowleyml@gmail.com>
To: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Cc: Michael Paquier <michael@paquier.xyz>, Ranier Vilela <ranier.vf@gmail.com>, Peter Smith <smithpb2250@gmail.com>, Peter Eisentraut <peter@eisentraut.org>, Heikki Linnakangas <hlinnaka@iki.fi>, pgsql-hackers@lists.postgresql.org
Date: 2024-11-06T19:10:17Z
Lists: pgsql-hackers
On Thu, 7 Nov 2024 at 00:40, Bertrand Drouvot
<bertranddrouvot.pg@gmail.com> wrote:
> Do you mean add:
>
> "
> for (; p < aligned_end; p += sizeof(size_t))
> {
>    if (*(size_t *)p != 0)
>        return false;
> }
> "
>
> just before the last loop?
>
> If so, I did a few tests and did not see any major improvements. So, I thought
> it's simpler to not add more code in this inline function in v7 shared up-thread.

Did you try with a size where there's a decent remainder, say 124
bytes? FWIW, one of the cases has 112 bytes, and I think that is
aligned memory meaning we'll do the first 64 in the SIMD loop and have
to do 48 bytes in the byte-at-a-time loop. If you had the loop Michael
mentioned, that would instead be 6 loops of size_t-at-a-time.

David



Commits

  1. Use pg_memory_is_all_zeros() in PageIsVerifiedExtended()

  2. Optimize pg_memory_is_all_zeros() in memutils.h

  3. Remove use of pg_memory_is_all_zeros() in bufpage.c

  4. Add pg_memory_is_all_zeros() in memutils.h