Horton

Re: define pg_structiszero(addr, s, r)

David Rowley <dgrowleyml@gmail.com>

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From: David Rowley <dgrowleyml@gmail.com>
To: Michael Paquier <michael@paquier.xyz>
Cc: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>, Peter Smith <smithpb2250@gmail.com>, Peter Eisentraut <peter@eisentraut.org>, Heikki Linnakangas <hlinnaka@iki.fi>, pgsql-hackers@lists.postgresql.org
Date: 2024-11-01T07:27:45Z
Lists: pgsql-hackers 
On Fri, 1 Nov 2024 at 20:14, Michael Paquier <michael@paquier.xyz> wrote:
> 2) On HEAD at 49d6c7d8daba:
> .LVL299:
>    .loc 1 131 16 is_stmt 0 discriminator 1 view .LVU524
>    cmpq    $8192, %rbx
>    je      .L419
>
> 3) With the patch sent at [1]:
> .LVL306:
>    .loc 3 201 23 is_stmt 1 discriminator 1 view .LVU545
>    cmpq    $8192, %rbx
>    jne     .L417
>
> So it does not matter one way or another for 2) or 3), does it?

The patch in [1] will fix the bug. But I'm still concerned about the
performance implications of moving to byte-at-a-time processing. There
are about 8 times more instructions being expected to do the same
work.

David

> [1]: https://www.postgresql.org/message-id/ZyR02ofHiWG1HmLI@paquier.xyz

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