Re: [PoC] Improve dead tuple storage for lazy vacuum

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
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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.


Andres Freund

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