nfs stalls and speed issues

[Antoine Jacoutot <ajacoutot_(_at_)_lphp_(_dot_)_org>]

Hi...

I know the question about NFS tunning comes regularly on the mailing 
lists, but once again, I'll try to get some help from NFS gurus.
While I don't care about huge NFS speed, I was wondering if there was a 
known problem in NFS from an OpenBSD client to an OpenBSD server.
Indeed, when transfering large files the speed is stuck between 700kb 
and 1mb/sec (obsd --> obsd) and the transfer often stalls for about 10 
seconds then restarts.
If using Linux, or FreeBSD as NFS client and OpenBSD as a server, the 
speed jumps to 5 to 6 Mb/sec, which is what I would love to get on my 
OpenBSD client.

Config:
OpenBSD is version 3.5 and the network is 100Mb full-duplex.
The NFS mounts options are: "rw,nodev,nosuid,-3,-U,-b,-i,-r8192,-w8192"
The sysctl vfs.nfs.iothreads is set to "4" on the client.
I also tried TCP mounts ; starting rpc.lockd ; change read and write sizes.
I disabled all pf rules.
Networks cards are: "3Com 3c905C 100Base-TX" (driver xl).

Note that transfers from OpenBSD client to Linux/FreeBSD servers are 
fast, only transfers from OpenBSD-->OpenBSD have issues.

Thanks in advance for any hints regarding this issue.
Regards,

Antoine