memory use?

This is more of a question than a problem report.

I stumbled across this project when I remember my old Amiga's `nul:` (`null:`?) device, which also allowed to discard all file output from applications that would, say, create multiple files under a directory hierarchy based on a single input name pattern.

Except that to the best of my knowledge, those files all behaved like `/dev/null` in that they were always 0 bytes (IIRC you could list any random file "on" that `nul:` device and it would show as existing but empty).

I understand that this `nullfs` project maintains some amount of state - how much memory does/can that consume, and under what conditions is that memory released back to the system? Is there a mount option that disables the advanced features and makes the filesystem behave like `/dev/null`?