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

On Fri, May 17, 2024 at 01:09:55PM -0400, Tom Lane wrote:
> Nathan Bossart <nathandbossart@gmail.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.

Cool.  I'll at least fix the back-branches as-is, but I'll see about
revamping this stuff for v18.

>> 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.

The advantage of the GUC is that its value could be seen before trying to
actually start the server.  I don't dispute that it's not the right way to
surface this information, though.

-- 
Nathan Bossart
Amazon Web Services: https://aws.amazon.com