Does anyone know what this service might be ...
runsvdir is the master process responsible for all supervised services, of which there are many in SME server. You should expect to see a single instance of it running always.
http://smarden.org/runit/runsvdir.8.html... and if it indicates a problem?
What you see under 'Command' are error messages from the 'runsv' processes that 'runsvdir' starts. You show multiple runsv processes unable to lock a file - that's likely because you are trying to start 'runsv' where one is already running. The error messages certainly indicate a problem - perhaps you, or someone/something, killed the original runsvdir process.
I suggest that you reboot the system. If you see any error messages in the runsvdir process table entry after reboot, then open a bug report.
If you see any more kernel panics, open a bug report.