nfsd and CPU/performance problem

[Marko Lerota]

My nfs server is chewing to much CPU even when nobody writes 
to nfs partition. The clients are RHES4. I don't know much about 
nfs but I followed the steps in handbook. Look:

last pid: 43588;  load averages:  0.46,  0.77,  0.81
28 processes:  1 running, 27 sleeping
CPU states:  0.0% user,  0.0% nice,  2.4% system,  0.2% interrupt, 97.4% idle
Mem: 9520K Active, 204M Inact, 142M Wired, 12K Cache, 112M Buf, 1648M Free
Swap: 4071M Total, 4071M Free

  PID USERNAME   THR PRI NICE   SIZE    RES STATE  C   TIME   WCPU COMMAND
  429 root         1   4    0  1204K   820K -      0 581:42 13.48% nfsd
  430 root         1   4    0  1204K   820K -      0  10:37  0.00% nfsd

Here is the config 
rc.conf
#######################
rpcbind_enable="YES"
portmap_enable="YES"
nfs_server_enable="YES"
nfs_server_flags="-u -t -n 4 -h 10.3.11.43"
mountd_flags="-r"
nfs_client_enable="YES"
#######################

/etc/exports
###########################################
/nfs   -alldirs      10.3.12.71 10.3.12.72
###########################################
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