Re: [PATCH] Hex-coding optimizations using SVE on ARM.

Chiranmoy.Bhattacharya@fujitsu.com <chiranmoy.bhattacharya@fujitsu.com>

From: "Chiranmoy.Bhattacharya@fujitsu.com" <Chiranmoy.Bhattacharya@fujitsu.com>

To: Nathan Bossart <nathandbossart@gmail.com>

Cc: John Naylor <johncnaylorls@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, David Rowley <dgrowleyml@gmail.com>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>, "Devanga.Susmitha@fujitsu.com" <Devanga.Susmitha@fujitsu.com>, "Ragesh.Hajela@fujitsu.com" <Ragesh.Hajela@fujitsu.com>

Date: 2025-09-11T10:43:56Z

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 →

Optimize hex_encode() and hex_decode() using SIMD.
- ec8719ccbfcd 19 (unreleased) landed
Speed up hex_encode with bytewise lookup
- e24d77080b36 18.0 landed

> Thanks.  I noticed that this stuff is simple enough that we can use
> port/simd.h (with a few added functions).  This is especially nice because
> it takes care of x86, too.  The performance gains look similar to what you
> reported for v6:

This looks good, much cleaner.
One possible improvement would be to use a vectorized table lookup instead of compare and add. I compared v6 and v7 Neon versions, and v6 is always faster.
I’m not sure if SSE2 has a table lookup similar to Neon.

arm - m7g.4xlarge
  buf  | v6-Neon| v7-Neon| % diff
-------+--------+--------+--------
    64 |   6.16 |   8.57 |  28.07
   128 |  11.37 |  15.77 |  27.87
   256 |  18.54 |  30.28 |  38.77
   512 |  33.98 |  62.15 |  45.33
  1024 |  64.46 | 117.55 |  45.16
  2048 | 124.28 | 254.86 |  51.24
  4096 | 243.47 | 509.23 |  52.19
  8192 | 487.34 | 953.81 |  48.91

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Chiranmoy