Horton

Re: define pg_structiszero(addr, s, r)

David Rowley <dgrowleyml@gmail.com>

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From: David Rowley <dgrowleyml@gmail.com>
To: Peter Eisentraut <peter@eisentraut.org>
Cc: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>, Ranier Vilela <ranier.vf@gmail.com>, Michael Paquier <michael@paquier.xyz>, Peter Smith <smithpb2250@gmail.com>, Heikki Linnakangas <hlinnaka@iki.fi>, pgsql-hackers@lists.postgresql.org
Date: 2024-11-06T19:05:10Z
Lists: pgsql-hackers 
On Thu, 7 Nov 2024 at 07:34, Peter Eisentraut <peter@eisentraut.org> wrote:
> Speaking of which, couldn't you just use
>
>      pg_popcount(ptr, len) == 0

That might be quite good for small lengths or for use cases where the
memory is always or almost always zero. The problem is there's no
early exit when you find the first non-zero which means, for larger
lengths, reading much more memory. That'll both take longer and
possibly evict cache lines which might be useful to have in the near
future.

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