| From: | Jeff Davis <pgsql(at)j-davis(dot)com> |
|---|---|
| To: | James Hunter <james(dot)hunter(dot)pg(at)gmail(dot)com> |
| Cc: | David Rowley <dgrowleyml(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Matthias van de Meent <boekewurm+postgres(at)gmail(dot)com>, PostgreSQL Developers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: Make tuple deformation faster |
| Date: | 2025-03-05 20:15:57 |
| Message-ID: | 542d28c7d22d392005076c85f6e5d6a38205997e.camel@j-davis.com |
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| Lists: | pgsql-hackers |
On Wed, 2025-03-05 at 11:33 -0800, James Hunter wrote:
> For a bitfield, however, the CPU has to read from or write to the
> byte
> that contains the bit, but then it also has to mask out the *other*
> bits in that bitfield. This is a data dependency, so it stalls the
> CPU
> pipeline.
Here the bits aren't changing, so we're only talking about mask-and-
test, right? My intuition is that wouldn't cause much of a problem.
Regards,
Jeff Davis
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