From top:
  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
14305 root      25   0 19388 4084  440 S 98.8  0.2   2899:01 rpc.mountd

MACHINE:~# cat /var/lib/nfs/rmtab|wc -l
250
MACHINE:~# cat /proc/net/rpc/nfsd|grep th
th 128 56883259 133294.866 60524.726 31542.261 5319.962 16142.680 11929.108 10629.967 10181.528 5611.520 109782.458

MACHINE:~# cat /etc/default/nfs-kernel-server
# Number of servers to start up
RPCNFSDCOUNT=128

# Runtime priority of server (see nice(1))
RPCNFSDPRIORITY=0

# Options for rpc.mountd.
# If you have a port-based firewall, you might want to set up
# a fixed port here using the --port option. For more information,
# see rpc.mountd(8) or http://wiki.debian.org/?SecuringNFS
RPCMOUNTDOPTS=