Horton

Re: add AVX2 support to simd.h

John Naylor <johncnaylorls@gmail.com>

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From: John Naylor <johncnaylorls@gmail.com>
To: Nathan Bossart <nathandbossart@gmail.com>
Cc: Ants Aasma <ants@cybertec.at>, pgsql-hackers@postgresql.org
Date: 2024-03-17T02:47:33Z
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. Improve style of pg_lfind32().

  2. Fix compiler warning for pg_lfind32().

  3. Micro-optimize pg_lfind32().

  4. Introduce helper SIMD functions for small byte arrays

  5. Optimize xid/subxid searches in XidInMVCCSnapshot().

On Sat, Mar 16, 2024 at 2:40 AM Nathan Bossart <nathandbossart@gmail.com> wrote:
>
> On Fri, Mar 15, 2024 at 12:41:49PM -0500, Nathan Bossart wrote:
> > I've also attached the results of running this benchmark on my machine at
> > HEAD, after applying 0001, and after applying both 0001 and 0002.  0001
> > appears to work pretty well.  When there is a small "tail," it regresses a
> > small amount, but overall, it seems to improve more cases than it harms.
> > 0002 does regress searches on smaller arrays quite a bit, since it
> > postpones the SIMD optimizations until the arrays are longer.  It might be
> > possible to mitigate by using 2 registers when the "tail" is long enough,
> > but I have yet to try that.
>
> The attached 0003 is a sketch of what such mitigation might look like.  It
> appears to help with the regressions nicely.  I omitted the benchmarking
> patch in v3 to appease cfbot.

I haven't looked at the patches, but the graphs look good.