15.5. Increasing the ring buffer size to reduce a high packet drop rate by using nmcli

Procedure

1. Display the packet drop statistics of the interface:

   # ethtool -S enp1s0
       ...
       rx_queue_0_drops: 97326
       rx_queue_1_drops: 63783
       ...

   Note that the output of the command depends on the network card and the driver.

   High values in discard or drop counters indicate that the available buffer fills up faster than the kernel can process the packets. Increasing the ring buffers can help to avoid such loss.

2. Display the maximum ring buffer sizes:

   # ethtool -g enp1s0
    Ring parameters for enp1s0:
    Pre-set maximums:
    RX:             4096
    RX Mini:        0
    RX Jumbo:       16320
    TX:             4096
    Current hardware settings:
    RX:             255
    RX Mini:        0
    RX Jumbo:       0
    TX:             255

   If the values in the Pre-set maximums section are higher than in the Current hardware settings section, you can change the settings in the next steps.

3. Identify the NetworkManager connection profile that uses the interface:

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

4. Update the connection profile, and increase the ring buffers:

   • To increase the RX ring buffer, enter:

     # nmcli connection modify Example-Connection ethtool.ring-rx 4096

   • To increase the TX ring buffer, enter:

     # nmcli connection modify Example-Connection ethtool.ring-tx 4096

5. Reload the NetworkManager connection:

   # nmcli connection up Example-Connection

   重要

   Depending on the driver your NIC uses, changing in the ring buffer can shortly interrupt the network connection.