Some NFS file transfers fail and hang automounting

From Linux NFS

Symptoms

• Given a file "foo" of 50Mb on a remote machine "remote".
  • This command will never finish

    <localmachine $> cp /remote_mount_point/foo bar 

  • bar will have a size less than foo.
  • automounting of the local machine is hung.

• The following message will show up in /var/log/messages

kernel: Callback slot table overflowed

If foo is lesser than 10Mb, the problem does'nt occur. After several tries with the source of 50Mb, the different sizes of the target file "bar" are random.

This incident occurs with: sunrpc.tcp_slot_table_entries = 16

but after tunning this parameter, all is fine with: sunrpc.tcp_slot_table_entries = 32