Horton

Re: OpenBSD versus semaphores

Mikael Kjellström <mikael.kjellstrom@mksoft.nu>

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From: Mikael Kjellström <mikael.kjellstrom@mksoft.nu>
To: Tom Lane <tgl@sss.pgh.pa.us>, pgsql-hackers@lists.postgresql.org
Cc: mikael.kjellstrom@gmail.com
Date: 2019-01-08T07:46:35Z
Lists: pgsql-hackers 
On 2019-01-08 07:14, Tom Lane wrote:
> I've been toying with OpenBSD lately, and soon noticed a seriously
> annoying problem for running Postgres on it: by default, its limits
> for SysV semaphores are only SEMMNS=60, SEMMNI=10.  Not only does that
> greatly constrain the number of connections for a single installation,
> it means that our TAP tests fail because you can't start two postmasters
> concurrently (cf [1]).
> 
> Raising the annoyance factor considerably, AFAICT the only way to
> increase these settings is to build your own custom kernel.

You don't need to build your custom kernel to change those settings.

Just add:

kern.seminfo.semmni=20

to /etc/sysctl.conf and reboot

/Mikael

Commits

  1. Doc: update our docs about kernel IPC parameters on *BSD.

  2. Pad semaphores to avoid false sharing.