| From: | Andres Freund <andres(at)anarazel(dot)de> |
|---|---|
| To: | John Naylor <john(dot)naylor(at)enterprisedb(dot)com> |
| Cc: | Hannu Krosing <hannuk(at)google(dot)com>, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>, Matthias van de Meent <boekewurm+postgres(at)gmail(dot)com>, Yura Sokolov <y(dot)sokolov(at)postgrespro(dot)ru>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: [PoC] Improve dead tuple storage for lazy vacuum |
| Date: | 2022-06-28 05:02:11 |
| Message-ID: | 20220628050211.c4rvrdy2qz2xnnek@alap3.anarazel.de |
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| Lists: | pgsql-hackers |
Hi,
On 2022-06-28 11:17:42 +0700, John Naylor wrote:
> On Mon, Jun 27, 2022 at 10:23 PM Hannu Krosing <hannuk(at)google(dot)com> wrote:
> >
> > > Another thought: for non-x86 platforms, the SIMD nodes degenerate to
> > > "simple loop", and looping over up to 32 elements is not great
> > > (although possibly okay). We could do binary search, but that has bad
> > > branch prediction.
> >
> > I am not sure that for relevant non-x86 platforms SIMD / vector
> > instructions would not be used (though it would be a good idea to
> > verify)
>
> By that logic, we can also dispense with intrinsics on x86 because the
> compiler will autovectorize there too (if I understand your claim
> correctly). I'm not quite convinced of that in this case.
Last time I checked (maybe a year ago?) none of the popular compilers could
autovectorize that code pattern.
Greetings,
Andres Freund
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