Re: define pg_structiszero(addr, s, r)

Bertrand Drouvot <bertranddrouvot.pg@gmail.com>

From: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
To: Ranier Vilela <ranier.vf@gmail.com>
Cc: Michael Paquier <michael@paquier.xyz>, David Rowley <dgrowleyml@gmail.com>, Peter Smith <smithpb2250@gmail.com>, Peter Eisentraut <peter@eisentraut.org>, Heikki Linnakangas <hlinnaka@iki.fi>, pgsql-hackers@lists.postgresql.org
Date: 2024-11-14T11:58:01Z
Lists: pgsql-hackers
Hi,

On Thu, Nov 14, 2024 at 08:22:23AM -0300, Ranier Vilela wrote:
> Em qui., 14 de nov. de 2024 às 07:09, Bertrand Drouvot <
> bertranddrouvot.pg@gmail.com> escreveu:
> 
> > Hi,
> >
> > On Thu, Nov 14, 2024 at 09:27:06AM +0900, Michael Paquier wrote:
> > > Makes sense to me to just do that, with a first < 8 loop, and a second
> > > for the 8~63 range.
> >
> > Thanks for looking at it!
> >
> > > There is also a "cant'" in the last size_t check.  Simple typo.
> >
> > Please find attached v12, with more comments and comments changes to
> > explain
> > the multiple cases (for safety) and phases (for efficiency).
> >
> Is it worth mentioning that pg_memory_is_all_zeros does not work correctly
> on 32-bit systems?
> 
> (63 < (size_t) * 8) /* 63 - 32*/

I think that the code is fully portable on 32-bit systems as it's using size_t
in all the places.

I agree that the comments are "64-bit" focused though, but I don't think that's
an issue (as I think it's already the case in multiple places in the core code).

Regards,

-- 
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com



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