Horton

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

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: "Imseih (AWS), Sami" <simseih@amazon.com>
Cc: Nathan Bossart <nathandbossart@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, Justin Pryzby <pryzby@telsasoft.com>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2024-05-17T19:28:20Z
Lists: pgsql-hackers 
Hi,

On 2024-05-17 18:30:08 +0000, Imseih (AWS), Sami wrote:
> > The advantage of the GUC is that its value could be seen before trying to
> > actually start the server.
>
> Only if they have a sample in postgresql.conf file, right?
> A GUC like shared_memory_size_in_huge_pages will not be.

You can query gucs with -C. E.g.

postgres -D pgdev-dev -c shared_buffers=16MB -C shared_memory_size_in_huge_pages
13
postgres -D pgdev-dev -c shared_buffers=16MB -c huge_page_size=1GB -C shared_memory_size_in_huge_pages
1

Which is very useful to be able to actually configure that number of huge
pages. I don't think a system view or such would not help here.

Greetings,

Andres Freund

Commits

  1. Introduce num_os_semaphores GUC.

  2. Fix documentation for POSIX semaphores.

  3. Fix documentation for System V semaphores.