Re: postgresql 18 and shm

[Rob Whitlock <rwhitlock22%gmail.com@localhost>]

> On Jul 15, 2026, at 9:42 AM, Greg Troxel <gdt%lexort.com@localhost> wrote:
> 
> Marc Baudoin <babafou%babafou.eu.org@localhost> writes:
> 
>> Greg Troxel <gdt%lexort.com@localhost> écrit :
>>> 
>>> What is kern.posix.semmax?  For me, it's 128, netbsd
>>> 9/10/11. i386/earmv7hf-el/amd64/aarch64.
>> 
>> 128 also (NetBSD default value).
> 
> I went to read the upstream docs, and they are quite comprehensive.
> 
> https://www.postgresql.org/docs/18/kernel-resources.html#SYSVIPC
> 
> It says that POSIX semaphores are not used on NetBSD; pgsql uses sysv,
> as makes sense from the commentary so far.
> 
>>>  Is this a change  in resource usage by pgsql18 for the same configured
>>>  connection limit, is it a change in the default connection limit, or
>>>  is it something else?
>> 
>> I would say something else.  Maybe related to the new
>> asynchronous I/O system in PostgreSQL 18.
> 
> It seems they changed the scheme by which they group semaphores into
> sets.
> 
> Having found that, I now think:
> 
>  1) Upstream documents this pretty well, but the error message doesn't
>     really point to it.
> 
>     It could make sense for the rc.d script, if limits are low to print
>     a "see $URL".  upstream is already addressing this, so we shouldn't
>     also.

Would it be possible to point to local documentation instead/as well?
I do not like this trend towards solely Internet-based documentation.
It turns Internet access into a requirement.