1.4. Increasing the transmit queue length of a NIC to reduce the number of transmit errors

Procedure

1. Display the current transmit queue length:

   # ip -s link show enp1s0
   2: enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000
   ...

   In this example, the transmit queue length (qlen) of the enp1s0 interface is 1000.

2. Monitor the dropped packets counter of a network interface’s software transmit queue:

   # tc -s qdisc show dev enp1s0
   qdisc fq_codel 0: root refcnt 2 limit 10240p flows 1024 quantum 1514 target 5ms interval 100ms memory_limit 32Mb ecn drop_batch 64
    Sent 16889923 bytes 426862765 pkt (dropped 191980, overlimits 0 requeues 2)
   ...

3. If you encounter a high or increasing transmit error count, set a higher transmit queue length:

   1. Identify the NetworkManager connection profile that uses this interface:

      # nmcli connection show
      NAME                UUID                                  TYPE      DEVICE
      Example-Connection  a5eb6490-cc20-3668-81f8-0314a27f3f75  ethernet  enp1s0

   2. Update the connection profile, and increase the transmit queue length:

      # nmcli connection modify Example-Connection link.tx-queue-length 2000

      Set the queue length to double of the current value.

   3. Apply the changes:

      # nmcli connection up Example-Connection

Verification

1. Display the transmit queue length:

   # ip -s link show enp1s0
   2: enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 2000
   ...

2. Monitor the dropped packets counter:

   # tc -s qdisc show dev enp1s0

   If the dropped counter still increases, double the transmit queue length again. Repeat this process until the counter no longer increases.