no immediate idea, but a quick test to help isolate which functionality
could be causing problems is to disable TSO on all four interfaces using
ethtool.
It could be that GSO is somehow playing into this as well, but I don't
know why (you could disable it with ethtool too).
It could be unrelated but I've noticed that TCP window size can grow much
larger now than it used to (especially talking to LRO enabled clients)
and this might cause some kind of an overflow in the TCP transmit
offloading hardware in the e1000 parts.
in your log I saw one tx timeout for each interface, one first one by itself
and then several more all within a few minutes, but then no more for
a really long time.
My first reaction is to ask you what test you're running, and ask you to
run the e1000_dump code (see google) to dump the tx descriptor rings at
the time of failure.
I can get you that code with updates if you're willing to test, but
it might take a couple of days.
Jesse--
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