NFS lockups with VMware esxi client

[David Ehrmann]

I have NFS sharing a ZFS pool that VMware esxi stores files on.  When 
put under stress (an OS installation, but not Linux compilation), the 
NFS server locks, spiking to 100% CPU usage.  Not even kill -KILL can 
stop the process, so rebooting is required.

  PID USERNAME    THR PRI NICE   SIZE    RES STATE   C   TIME   WCPU COMMAND
  885 root          4  44    0  5804K   988K CPU2    0 239:39 100.00% nfsd

Other people have run into this problem, but I never found a solution.  
I'm running 8.1-PRERELEASE on amd64, but I think others have seen the 
problem on 8.1-RELEASE.

zpool status reports that the pool is healthy, so that's not it.  My 
only two ideas are hosting on something other than ZFS and trying to 
reproduce it with a lot of big, random NFS requests.  Any other ideas?