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base repository: postgresql-cfbot/postgresql
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  • 3 commits
  • 11 files changed
  • 4 contributors

Commits on Apr 3, 2025

  1. Improve CRC32C performance on recent x86_64 platforms 

    The previous implementation of CRC32C on x86 relied on the native
CRC32 instruction from the SSE 4.2 extension, which operates on
up to 8 bytes at a time. We can get a substantial speedup by using
carryless multiplication on SIMD registers, processing 64 bytes per
loop iteration. Shorter inputs fall back to ordinary CRC instructions.

The VPCLMULQDQ instruction on 512-bit registers has been available
on Intel hardware since 2019 and AMD since 2022. There is an older
variant for 128-bit registers, but at least on Zen 2 it performs worse
than normal CRC instructions for short inputs. (Thanks to David Rowley
for testing on that platform.)

We must now do a runtime check, even for builds that target SSE
4.2. This doesn't matter in practice for WAL (arguably the most
critical case), because since commit af0c248 the final computation
with the 20-byte WAL header is inlined and unrolled. Compared with
two direct function calls, testing showed equal or slightly faster
performance in performing an indirect function call on several dozen
bytes followed by inlined instructions on constant input of 20 bytes.

The MIT-licensed implementation was generated with the "generate"
program from

https://github.com/corsix/fast-crc32/

Based on: "Fast CRC Computation for Generic Polynomials Using PCLMULQDQ
Instruction" V. Gopal, E. Ozturk, et al., 2009

Co-authored-by: Raghuveer Devulapalli <[email protected]>
Co-authored-by: Paul Amonson <[email protected]>
Reviewed-by: Nathan Bossart <[email protected]>
Reviewed-by: Andres Freund <[email protected]> (earlier version)
Tested-by: Raghuveer Devulapalli <[email protected]>
Tested-by: Matthew Sterrett <[email protected]> (earlier version)
Discussion: https://postgr.es/m/BL1PR11MB530401FA7E9B1CA432CF9DC3DC192@BL1PR11MB5304.namprd11.prod.outlook.com
Discussion: https://postgr.es/m/PH8PR11MB82869FF741DFA4E9A029FF13FBF72@PH8PR11MB8286.namprd11.prod.outlook.com
    @j-naylor @r-devulap
    3 people authored and Commitfest Bot committed Apr 3, 2025
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  2. Add debug for CI XXX not for commit

    @j-naylor
    j-naylor authored and Commitfest Bot committed Apr 3, 2025
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  3. [CF 5545] v16 - Improve CRC32C performance with AVX-512, take 2 

    This branch was automatically generated by a robot using patches from an
email thread registered at:

https://commitfest.postgresql.org/patch/5545

The branch will be overwritten each time a new patch version is posted to
the thread, and also periodically to check for bitrot caused by changes
on the master branch.

Patch(es): https://www.postgresql.org/message-id/CANWCAZZ_+65KW3qUks2y15142zLYLfx0JK-wWWCJziDkR971Eg@mail.gmail.com
Author(s): Raghuveer Devulapalli
    Commitfest Bot committed Apr 3, 2025
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