Comment 41 for bug 1006446

It seems that issue is easy to reproduce: I just did it using just two VirtualBox VMs wit the following steps:

1. Install Ubuntu 12.04.1 Server x64 with default settings (also default settings of Virtual box)
2. Update all packages (apt-get update, apt-get dist-upgrade)
3. Clone VM - rename one to server, the other to client and set bridged network interfaces, add DHCP assigned ip addresses to /etc/hosts
4. install nfs-kernel-server package on server
5. create directory /export and add following line to /etc/exports:
/export client(rw,no_root_squash,async,subtree_check)
6. export with "exportfs -a"
7. install nfs-common package on client
8. mount nfs share: sudo mount -t nfs server:/export /mnt
9. write a file: sudo dd if=/dev/zero of=/mnt/t1 bs=1M count=10000
10. check load on server with 'top': 40% distributed over 4 threads

I hope this helps. I can make the VMs available if somebody is interested.

Unless this is fixed or a workaround is found, I will have to downgrade my servers again :-(