sysv semaphores

[Damian Wiest]

On Tue, Nov 14, 2006 at 03:22:33PM +0000, Robin Becker wrote:
> I'm trying to test a python extension (POSH) that uses semaphores. When 
> testing I get a run time error that indicates it requires too many 
> semaphores. Is it possible to adjust the allowed number of semaphores 
> without rebuilding the kernel?
> 
> What are the costs of having semaphores ie are they memory/cpu intensive?
> -- 
> Robin Becker

You'll want to use either sysctl(8) to change the settings dynamically, or
use /etc/sysctl.conf to modify the settings permanently.  I'm not sure if
there's a benefit to rolling a new kernel versus using sysctl.conf, or if
things even work that way anymore.

# sysctl -a | grep seminfo

kern.seminfo.semmni=10    # number of semaphore identifiers
kern.seminfo.semmns=60    # number of semaphores in system
kern.seminfo.semmnu=30    # number of undo structures in system
kern.seminfo.semmsl=60    # max number of semaphores per id
kern.seminfo.semopm=100   # max number of operations per semop call
kern.seminfo.semume=10    # max number of undo entries per process
kern.seminfo.semusz=100   # size in bytes of undo structure
kern.seminfo.semvmx=32767 # semaphore maximum value
kern.seminfo.semaem=16384 # adjust on exit max value

Those comments are from /usr/include/sys/sem.h

-Damian