dovz:~# cat /proc/filesystems
nodev   sysfs
nodev   rootfs
nodev   bdev
nodev   proc
nodev   cpuset
nodev   debugfs
nodev   sockfs
nodev   pipefs
nodev   futexfs
nodev   tmpfs
nodev   inotifyfs
nodev   eventpollfs
nodev   devpts
        cramfs
nodev   ramfs
nodev   mqueue
nodev   usbfs
        ext3
nodev   rpc_pipefs
nodev   nfsd
nodev   simfs
nodev   nfs
nodev   nfs4


dovz:~# lsmod |grep sim
simfs                   5068  2