NFS from virtualbox guest is much slower than NFS from another machine

[Yuri]

I have 6.5GB chromium debug build directory shared through NFS.
When I try building it on FreeBSD i386 guest running on the same host 
where NFS server is, it takes 11 sec of intense NFS before it begins to 
compile.
But when I try building the same directory from another FreeBSD i386 
machine on the 100Mb LAN, it begins to build after only 3 sec of intense 
NFS.

Same NFS operations take 11 sec from the local vbox guest and 3 sec from 
the remote host over 100Mb link.

This is very strange, local NFS should be blazing fast, and I see the 
opposite picture. For some reason local NFS is crippled.

Anybody can explain why is this happening?

9.0 STABLE
vbox-4.1.12

Yuri

PS I removed lockf operation from the Makefile since lockf fails over NFS