Re: problems with "Shared Memory and Semaphores" section of docs

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Nathan Bossart <nathandbossart(at)gmail(dot)com>
Cc: "Imseih (AWS), Sami" <simseih(at)amazon(dot)com>, Justin Pryzby <pryzby(at)telsasoft(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: problems with "Shared Memory and Semaphores" section of docs
Date: 2024-05-17 17:09:55
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Nathan Bossart <nathandbossart(at)gmail(dot)com> writes:
> [ many, many problems in documented formulas ]

> At a bare minimum, we should probably fix the obvious problems, but I
> wonder if we could simplify this section a bit, too.

Yup. "The definition of insanity is doing the same thing over and
over and expecting different results." Time to give up on documenting
these things in such detail. Anybody who really wants to know can
look at the source code.

> If the exact values
> are important, maybe we could introduce more GUCs like
> shared_memory_size_in_huge_pages that can be consulted (instead of
> requiring users to break out their calculators).

I don't especially like shared_memory_size_in_huge_pages, and I don't
want to introduce more of those. GUCs are not the right way to expose
values that you can't actually set. (Yeah, I'm guilty of some of the
existing ones like that, but it's still not a good thing.) Maybe it's
time to introduce a system view for such things? It could be really
simple, with name and value, or we could try to steal some additional
ideas such as units from pg_settings.

regards, tom lane

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