I'm not sure this is a bug or feature. First, I've been away for a few weeks being on vacation and other stuff. My client liked my findings on DPDK well enough that I have been loaned a dual-cpu system (2 Xeon E5-2690 @ 2.9 GHz) and two 82599 cards. This is so I can eliminate the PCIe bus contention and to test the Numa capabilities.
So I am now seeing (almost) line rate (~14.32 Mpps) between the two cards. But it is not quite line rate (14.88 Mpps), so I have started playing around with the TX/RX threshold parameters. Reading the datasheet for the 82599, section 7.2.3.5.1 seems to indicate that the write threshold (TXDCTL[n].WTHRESH) should (could?) set this value to obtain more efficient use of the PCIe bus and memory. However, testpmd fails because the TX rs threshold (set to 0 by testpmd) is defaulting to 32 inside the ixgbe pmd code, which then fails because I have set the TX write threshold to 16. And I cannot force the TX rs threshold < 0 via the command line. Personally I think this is a bug, but maybe it's a feature :-) but is there a reason to force use of the rs threshold over the write threshold? Thanks, Patrick
