Small % of rx_discards growing on one interface

Issue

• It was observed that one interface is receiving a low number of discards, why is this occurring since we have
  already done the following:

1 . Increased the ring buffer to maximum
2 . Running irqbalance
3 . Disabled c-states

10:31:03.787536651+03:00 rx_ucast_packets: 132730143 rx_discards: 5295
10:31:43.144604383+03:00 rx_ucast_packets: 132761736 rx_discards: 5443
11:16:44.211871658+03:00 rx_ucast_packets: 135041128 rx_discards: 5443
11:17:23.983925718+03:00 rx_ucast_packets: 135074009 rx_discards: 5821
12:41:18.931342954+03:00 rx_ucast_packets: 139549402 rx_discards: 5821
12:41:58.385202743+03:00 rx_ucast_packets: 139585819 rx_discards: 6179
13:21:52.603005196+03:00 rx_ucast_packets: 141767087 rx_discards: 6179
13:22:32.402725931+03:00 rx_ucast_packets: 141804691 rx_discards: 6282
14:06:52.091550829+03:00 rx_ucast_packets: 144272528 rx_discards: 6282
14:07:31.497319653+03:00 rx_ucast_packets: 144309451 rx_discards: 6355
14:26:43.065228493+03:00 rx_ucast_packets: 145370348 rx_discards: 6355
14:27:23.266186366+03:00 rx_ucast_packets: 145407872 rx_discards: 6488

It was noted that the following errors were being received in /var/log/messages

> dmar: DRHD: handling fault status reg 2 
> dmar: DMAR:[DMA Write] Request device [02:00.1] fault addr 791dc000 
> DMAR:[fault reason 05] PTE Write access is not set 
> dmar: DMAR:[DMA Write] Request device [02:00.1] fault addr 791dc000 
> DMAR:[fault reason 05] PTE Write access is not set 
> dmar: DMAR:[DMA Write] Request device [02:00.1] fault addr 791dc000 
> DMAR:[fault reason 05] PTE Write access is not set