Possible transmit/stats problem in igb driver.

[Sreekanth Rupavatharam]

I am seeing a strange issue with transmit with igb driver and wanted to check with you if this issue is already noted. I didn’t find anything particularly matching in Bugzilla. There is a test I am running where a iXIa is sending arps at about 500/sec for 10 seconds. This test works fine if the incoming packet size is 64 bytes, but if the packets are larger than 64 bytes, then I see that the counter in dev.igb.1.queue0.tx_packets shows the correct value(about 5000), but dev.igb.1.mac_stats.total_pkts_txd doesn’t reflect that.


Before
dev.igb.1.queue0.tx_packets: 24907933
dev.igb.1.mac_stats.total_pkts_txd: 16647169

After
dev.igb.1.queue0.tx_packets: 24913324
dev.igb.1.mac_stats.total_pkts_txd: 16647545                                    |


queue0.tx_packets difference = 24913324 – 24907933 = 5391
mac_stats.total_pkts_txd difference = 16647545 – 16647169 = 376

I do not see any errors in the stats(I can post the complete stats if you wish) nor do I see pause frames being received. Is there an explanation as to why the packets are dispatched to the hardware but are not transmitted on to the wire?