Horton

RE: Popcount optimization using AVX512

Amonson, Paul D <paul.d.amonson@intel.com>

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From: "Amonson, Paul D" <paul.d.amonson@intel.com>
To: "Amonson, Paul D" <paul.d.amonson@intel.com>, Nathan Bossart <nathandbossart@gmail.com>
Cc: Andres Freund <andres@anarazel.de>, Alvaro Herrera <alvherre@alvh.no-ip.org>, "Shankaran, Akash" <akash.shankaran@intel.com>, Noah Misch <noah@leadboat.com>, Tom Lane <tgl@sss.pgh.pa.us>, "Matthias van de Meent" <boekewurm+postgres@gmail.com>, "pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>
Date: 2024-03-15T17:43:39Z
Lists: pgsql-hackers

Commits

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  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.

> -----Original Message-----
> From: Amonson, Paul D <paul.d.amonson@intel.com>
> Sent: Friday, March 15, 2024 8:31 AM
> To: Nathan Bossart <nathandbossart@gmail.com>
...
> When I tested the code outside postgres in a micro benchmark I got 200-
> 300% improvements. Your results are interesting, as it implies more than
> 300% improvement. Let me do some research on the benchmark you
> referenced. However, in all cases it seems that there is no regression so should
> we move forward on merging while I run some more local tests?

When running quick test with small buffers (1 to 32K) I see up to about a 740% improvement. This was using my stand-alone micro benchmark outside of PG. My original 200-300% numbers were averaged including sizes up to 512MB which seems to not run as well on large buffers.  I will try the referenced micro benchmark on Monday. None of my benchmark testing used the command line "time" command. For Postgres is set "\timing" before the run and for the stand-alone benchmark is took timestamps in the code. In all cases I used -O2 for optimization.

Thanks,
Paul