More on NFS and Dtrace.

Mike also asked how to figure out what static trace points exist, of course dtrace
will tell us (and make a jolly good pot of tea as well :) )

root@zmaxdp : dtrace -m sdt:nfs* -l
   ID   PROVIDER            MODULE                          FUNCTION NAME
29166        sdt               nfs                validate_idmapping nfs4-acl-nobody
29167        sdt               nfs                    errs_to_action nfs4-expired
29168        sdt               nfs                         nfs4renew nfs4-renew-end
29169        sdt               nfs                         nfs4renew nfs4-renew-start
29170        sdt               nfs                      nfs4_rfscall nfs4-rfscall_debug
29171        sdt               nfs                 nfs_idmap_str_gid nfs4-str-gid
29172        sdt               nfs                 nfs_idmap_str_uid nfs4-str-uid

The other portion of the question of how we figure out what data is
collected at these points is (unfortunately) a little harder to find out
and for now we'll need to refer to the source code.