on 9.2-stable nfs/zfs and 10g hang

[Daniel Braniss]

On Jan 17, 2014, at 4:47 PM, Rick Macklem <rmacklem at uoguelph.ca> wrote:

> 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).
> 
BINGO! disabling tso did it. I’ll try reducing the packet size later.
some numbers:
there where some 7*10^6 files
doing it locally (the find + md5) took about 3hs,
via nfs at 1g took 11 hrs.
at 10g it took 4 hrs.

thanks!
	danny


> 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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