Horton

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

John Naylor <johncnaylorls@gmail.com>

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From: John Naylor <johncnaylorls@gmail.com>
To: Nathan Bossart <nathandbossart@gmail.com>
Cc: "Chiranmoy.Bhattacharya@fujitsu.com" <Chiranmoy.Bhattacharya@fujitsu.com>, "Devanga.Susmitha@fujitsu.com" <Devanga.Susmitha@fujitsu.com>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>, "Ragesh.Hajela@fujitsu.com" <Ragesh.Hajela@fujitsu.com>
Date: 2025-01-14T05:27:30Z
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. Optimize hex_encode() and hex_decode() using SIMD.

  2. Speed up hex_encode with bytewise lookup

Attachments

On Sat, Jan 11, 2025 at 3:46 AM Nathan Bossart <nathandbossart@gmail.com> wrote:
>
> I was able to get auto-vectorization to take effect on Apple clang 16 with
> the following addition to src/backend/utils/adt/Makefile:
>
>         encode.o: CFLAGS += ${CFLAGS_VECTORIZE} -mllvm -force-vector-width=8
>
> This gave the following results with your hex_encode_test() function:
>
>     buf  | HEAD  | patch | % diff
>   -------+-------+-------+--------
>       16 |    21 |    16 |   24
>       64 |    54 |    41 |   24
>      256 |   138 |   100 |   28
>     1024 |   441 |   300 |   32
>     4096 |  1671 |  1106 |   34
>    16384 |  6890 |  4570 |   34
>    65536 | 27393 | 18054 |   34

We can do about as well simply by changing the nibble lookup to a byte
lookup, which works on every compiler and architecture:

select hex_encode_test(1000000, 1024);
master:
Time: 1158.700 ms
v2:
Time:  777.443 ms

If we need to do much better than this, it seems better to send the
data to the client as binary, if possible.

-- 
John Naylor
Amazon Web Services