I pretty much followed these instructions, but one extra step was required.

The problem that I was having was that the system kept running out of file descriptors and becoming unusable. After a little digging around with fstat and such, it was apparent that gam_server from Gamin was the culprit, using some 3700 file descriptors. From a bit of web browsing, I saw that this is somewhat common on BSD, because BSDs don’t have inotify like Linux, so Gamin uses kqueue but this requires opening files and using file descriptors. This is described in the Gamin Wikipedia page.

My solution was to increase the number of file descriptors by adding to /boot/loader.conf:

kern.maxfiles="25000"

This was enough file descriptors to placate gam_server:

[marca@freebsd9-0 ~/src]$ fstat | grep gam_server | wc -l
    6435