RE: Popcount optimization using AVX512 - Mailing list pgsql-hackers

From Amonson, Paul D
Subject RE: Popcount optimization using AVX512
Date
Msg-id BL1PR11MB53042473B7B53B96E43648A7DC292@BL1PR11MB5304.namprd11.prod.outlook.com
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In response to Re: Popcount optimization using AVX512  (Nathan Bossart <nathandbossart@gmail.com>)
Responses Re: Popcount optimization using AVX512
List pgsql-hackers
> -----Original Message-----
> From: Nathan Bossart <nathandbossart@gmail.com>
> Sent: Monday, March 11, 2024 6:35 PM
> To: Amonson, Paul D <paul.d.amonson@intel.com>

> Thanks.  There's no need to wait to post the AVX portion.  I recommend using
> "git format-patch" to construct the patch set for the lists.

After exploring git format-patch command I think I understand what you need. Attached.

> > What exactly do you suggest here? I am happy to always call either
> > pg_popcount32() or pg_popcount64() with the understanding that it may
> > not be optimal, but I do need to know which to use.
>
> I'm recommending that we don't change any of the code in the pg_popcount()
> function (which is renamed to pg_popcount_slow() in your v6 patch).  If
> pointers are 8 or more bytes, we'll try to process the buffer in 64-bit chunks.
> Else, we'll try to process it in 32-bit chunks.  Any remaining bytes will be
> processed one-by-one.

Ok, we are on the same page now. :)  It is already fixed that way in the refactor patch #1.

As for new performance numbers: I just ran a full suite like I did earlier in the process. My latest results an
equivalentto a pgbench scale factor 10 DB with the target column having varying column widths and appropriate random
dataare 1.2% improvement with a 2.2% Margin of Error at a 98% confidence level. Still seeing improvement and no
regressions.

As stated in the previous separate chain I updated the code removing the extra "extern" keywords.

Thanks,
Paul


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