on 9.2-stable nfs/zfs and 10g hang

[Rick Macklem]

Daniel Braniss wrote:
> hi all,
> 
> All was going ok till I decided to connect this host via a 10g nic
> and very soon it started
> to hang. Running multiple make buildworlds from other hosts connected
> via 10g and
> using both src and obj on the server via tcp/nfs did ok. but running
> 	find … -exec md5 {} + (the find finds over 6M files)
> from another host (at 10g) will hang it very quickly.
> 
> If I wait a while (can’t be more specific) it sometimes recovers -
> but my users are not very
> patient :-)
> 
This suggests that an RPC request/reply gets dropped in a way that TCP
doesn't recover. Eventually (after up to about 15min, I think?) the TCP
connection will be shut down and a new TCP connection started, with a
retry of outstanding RPCs.

> I will soon try the same experiment using the old 1G nic, but in the
> meantime, if someone
> could shed some light would be very helpful
> 
> I’m attaching core.txt, but if it doesn’t make it, it’s also
> available at:
> 	ftp://ftp.cs.huji.ac.il/users/danny/freebsd/core.txt.16
> 
You might try disabling TSO on the net interface. There are been issues
with TSO for segments around 64K in the past (or use rsize=32768,wsize=32768
options on the client mount, to avoid RPCs over about 32K in size).

Beyond that, capturing a packet trace for the case that hangs easily and
looking at what goes on near the end of it in wireshark might give you
a hint about what is going on.

rick

> thanks,
> 	danny
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