vge traffic problem

[David Ehrmann]

Pyun YongHyeon wrote:
> It seems iperf on FreeBSD was broken. It incorrectly generates
> huge-packet with IP length 0 so other host disconnected the
> TCP connection. Not sure it could be related with threading though.
> Use netperf instead, it would be more reliable than iperf.
>   
I saw a lot of warnings when I opened the cap file in Wireshark about 
the length in the IP header being wrong.  I'll start looking into netperf

> It's normal see some dropped frames under high network load. And
> you can't compare gigabit controller to fast ethernet controller.
>   
Very true, and that's why I tried a lower load.  I was a little 
surprised to see it choking at just 1 Mb/s (that's bits, not bytes), though.
> I have exact the same revision of the hardware and I don't have
> encountered your issue here. Instead of measuring performance
> number with broken iperf, check whether you still get
> "Connection reset by peer" message with csup(1) when you use vge(4)
> interface. If you still see the message, please send me tcpdump
> capture in private.
>   
csup is still working.

I actually think I *might* have the problem solved.  Switching the mount 
from UDP (why it was the default for NFS in this Linux distro, I don't 
know) to TCP seems to have fixed it.  My guess is that some sort of race 
condition occurred or there's a bug in someone's NFS flow control 
mechanism.  A 10x CPU and network performance difference must be more 
than is usually tested.  I hope.

I'll keep testing NFS over TCP and see if it fixed my problem.