| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com> |
| Cc: | David Rowley <dgrowleyml(at)gmail(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Robert Haas <robertmhaas(at)gmail(dot)com>, Yura Sokolov <y(dot)sokolov(at)postgrespro(dot)ru>, PostgreSQL Developers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: Reducing the chunk header sizes on all memory context types |
| Date: | 2022-08-30 14:17:34 |
| Message-ID: | 3613565.1661869054@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
I wrote:
> So maybe we should revisit the question. It'd be worth collecting some
> stats about how much extra space would be needed if we force there
> to be room for a sentinel.
Actually, after ingesting more caffeine, the problem with this for aset.c
is that the only way to add space for a sentinel that didn't fit already
is to double the space allocation. That's a little daunting, especially
remembering how many places deliberately allocate power-of-2-sized
arrays.
You could imagine deciding that the space classifications are not
power-of-2 but power-of-2-plus-one, or something like that. But that
would be very invasive to the logic, and I doubt it's a good idea.
regards, tom lane
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