Horton

Re: Popcount optimization using AVX512

David Rowley <dgrowleyml@gmail.com>

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From: David Rowley <dgrowleyml@gmail.com>
To: Nathan Bossart <nathandbossart@gmail.com>
Cc: Ants Aasma <ants.aasma@cybertec.at>, Alvaro Herrera <alvherre@alvh.no-ip.org>, "Amonson, Paul D" <paul.d.amonson@intel.com>, Tom Lane <tgl@sss.pgh.pa.us>, Andres Freund <andres@anarazel.de>, "Shankaran, Akash" <akash.shankaran@intel.com>, Noah Misch <noah@leadboat.com>, Matthias van de Meent <boekewurm+postgres@gmail.com>, "pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>
Date: 2024-04-04T03:28:58Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Fix __attribute__((target(...))) usage.

  2. Use __attribute__((target(...))) for AVX-512 support.

  3. Fix code for probing availability of AVX-512.

  4. Optimize visibilitymap_count() with AVX-512 instructions.

  5. Optimize pg_popcount() with AVX-512 instructions.

  6. Inline pg_popcount() for small buffers.

  7. Avoid function call overhead of pg_popcount() in syslogger.c.

  8. Refactor code for setting pg_popcount* function pointers.

  9. Inline pg_popcount{32,64} into pg_popcount().

  10. Remove MSVC scripts

  11. Use ARMv8 CRC instructions where available.

  12. Use Intel SSE 4.2 CRC instructions where available.

On Thu, 4 Apr 2024 at 11:50, Nathan Bossart <nathandbossart@gmail.com> wrote:
> If we can verify this approach won't cause segfaults and can stomach the
> regression between 8 and 16 bytes, I'd happily pivot to this approach so
> that we can avoid the function call dance that I have in v25.
>
> Thoughts?

If we're worried about regressions with some narrow range of byte
values, wouldn't it make more sense to compare that to cc4826dd5~1 at
the latest rather than to some version that's already probably faster
than PG16?

David