TSO and FreeBSD vs Linux

[David Wolfskill]

On Wed, Sep 04, 2013 at 03:03:12PM -0700, Adrian Chadd wrote:
> Hiya,
> 
> David - can you put together a minimal test case that others can reproduce?
> I have a bunch of gige intel NICs that I can try this with when I'm back in
> the office.
> ...

On NFS client machine (w/ Intel NICs):
* Ensure that net.inet.tcp.tso=1.
* Create or gain access to a regular file, size > 2^21 bytes.
* In my case, "ifconfig em0" showed both TSO4 & VLAN_HWTSO.  I have not
  experimented to determine whether either or both of those is required
  -- and in my case, the machine is my desktop here at work: I would
  prefer to avoid breaking it. :-}
* Mount a writable file system with adequate free space via NFS.
* Write the file (e.g., via cp(1)).

If that fails to re-create the problem, perhaps you'll need to have
another NIC and run IPFW & natd.  Something similar to the stock
"simple" configuration (/etc/rc.firewall) should do.

During the write, I would run "tcpdump -s 0 -w /tmp/cp.bpf host $NFS_server",
then look at the captured traffic later.  I used wireshark; it pointed
out the retransmissions.

Peace,
david
-- 
David H. Wolfskill				david at catwhisker.org
Taliban: Evil cowards with guns afraid of truth from a 14-year old girl.

See http://www.catwhisker.org/~david/publickey.gpg for my public key.
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