Bad interaction between 82599 hardware RSC and VLANs

[Andrew Boyer]

Hello Jack,
I'm seeing an issue on 82599 controllers.  When hardware RSC is used, large VLAN packets arrive without the VP bit set, even though the vtag in the descriptor is correct.  It totally kills the receive performance.  Turning off hardware RSC in the driver (falling back to software LRO) works fine, as does turning off LRO entirely.

I've worked around the problem for now by overriding the VP bit if ixgbe_rxeof() finds a valid vtag in the descriptor.

Have you seen this before?

It's not in the latest errata.  It almost seems to be the opposite of what Ryan reported in November 2010 ("82599 receiving packets with vlan tag=0 (vlan strip problem)?").

Thanks,
  Andrew

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Andrew Boyer	aboyer at averesystems.com