Terrible NFS performance under 9.2-RELEASE?

[Christian Weisgerber]

Rick Macklem <rmacklem at uoguelph.ca> wrote:

> I have a "hunch" that might explain why 64K NFS reads/writes perform
> poorly for some network environments.
> A 64K NFS read reply/write request consists of a list of 34 mbufs when
> passed to TCP via sosend() and a total data length of around 65680bytes.
> Looking at a couple of drivers (virtio and ixgbe), they seem to expect
> no more than 32-33 mbufs in a list for a 65535 byte TSO xmit. I think
> (I don't have anything that does TSO to confirm this) that NFS will pass
> a list that is longer (34 plus a TCP/IP header).

This may or may not be the same problem:

When I switched my desktop box from FreeBSD 7 to 9, NFS read
performance from my media server (running OpenBSD) became extremely
poor.  I couldn't even stream a movie any longer.  Disabling TSO
on the nfe(4) interface had no effect.  My workaround was to switch
from a TCP mount to a UDP one.  The problem has persisted to FreeBSD 10.

I can now report that switching to [rw]size=32768 with a TCP mount
also works fine.

-- 
Christian "naddy" Weisgerber                          naddy at mips.inka.de