[Linux-cluster] Groupd semaphore limits

[Juan Ramon Martin Blanco]

Hi folks!

Is it anywhere documented how many semaphores groupd uses for each gfs
filesystem that is mounted? Is it anywhere documented what is the
maximum number of gfs filesystems that can be mounted on a cluster?
We have had an issue in our production server with gfs filesystems not
being mounted and groupd consuming 100% cpu. Stracing it we saw it
could not create any new semaphore (with semget). After increasing
limits (modifying sysctl kernel.sem variable), everything is working
fine.
The default limit on rhel 5.3 is 128 semaphore matrix (each matrix has
3 semaphores). Mounting a gfs filesystem seems to consume 6
semaphores, so a maximum of 64 can be mounted.

I hope it can help anybody facing this problem in the future. I would
be fine if you document it somewhere.

Greetings,
Juanra