Chapter 34. Configuring ethtool coalesce settings

Using interrupt coalescing, the system collects network packets and generates a single interrupt for multiple packets. This increases the amount of data sent to the kernel with one hardware interrupt, which reduces the interrupt load, and maximizes the throughput.

This section provides different options to set the ethtool coalesce settings.

34.1. Coalesce settings supported by NetworkManager

You can set the following ethtool coalesce settings using NetworkManager:

  • coalesce-adaptive-rx
  • coalesce-adaptive-tx
  • coalesce-pkt-rate-high
  • coalesce-pkt-rate-low
  • coalesce-rx-frames
  • coalesce-rx-frames-high
  • coalesce-rx-frames-irq
  • coalesce-rx-frames-low
  • coalesce-rx-usecs
  • coalesce-rx-usecs-high
  • coalesce-rx-usecs-irq
  • coalesce-rx-usecs-low
  • coalesce-sample-interval
  • coalesce-stats-block-usecs
  • coalesce-tx-frames
  • coalesce-tx-frames-high
  • coalesce-tx-frames-irq
  • coalesce-tx-frames-low
  • coalesce-tx-usecs
  • coalesce-tx-usecs-high
  • coalesce-tx-usecs-irq
  • coalesce-tx-usecs-low

34.2. Configuring ethtool coalesce settings using NetworkManager

This section describes how to set ethtool coalesce settings using NetworkManager, as well as how you remove the setting from a NetworkManager connection profile.

Procedure

  1. For example, to set the maximum number of received packets to delay to 128 in the enp1s0 connection profile, enter:

    # nmcli connection modify enp1s0 ethtool.coalesce-rx-frames 128
  2. To remove a coalesce setting, set the setting to ignore. For example, to remove the ethtool.coalesce-rx-frames setting, enter:

    # nmcli connection modify enp1s0 ethtool.coalesce-rx-frames ignore
  3. To reactivate the network profile:

    # nmcli connection up enp1s0

Verification steps

  1. Use the ethtool -c command to display the current offload features of a network device:

    # ethtool -c network_device

34.3. Using System Roles to configure ethtool coalesce settings

You can use the networking RHEL System Role to configure ethtool coalesce settings of a NetworkManager connection.

Important

When you run a play that uses the networking RHEL System Role, the System Role overrides an existing connection profile with the same name if the settings do not match the ones specified in the play. Therefore, always specify the whole configuration of the network connection profile in the play, even if, for example the IP configuration, already exists. Otherwise the role resets these values to their defaults.

Depending on whether it already exists, the procedure creates or updates the enp1s0 connection profile with the following settings:

  • A static IPv4 address - 198.51.100.20 with a /24 subnet mask
  • A static IPv6 address - 2001:db8:1::1 with a /64 subnet mask
  • An IPv4 default gateway - 198.51.100.254
  • An IPv6 default gateway - 2001:db8:1::fffe
  • An IPv4 DNS server - 198.51.100.200
  • An IPv6 DNS server - 2001:db8:1::ffbb
  • A DNS search domain - example.com
  • ethtool coalesce settings:

    • RX frames: 128
    • TX frames: 128

Prerequisites

  • The ansible-core and rhel-system-roles packages are installed on the control node.
  • If you use a different remote user than root when you run the playbook, this user has appropriate sudo permissions on the managed node.

Procedure

  1. If the host on which you want to execute the instructions in the playbook is not yet inventoried, add the IP or name of this host to the /etc/ansible/hosts Ansible inventory file:

    node.example.com
  2. Create the ~/configure-ethernet-device-with-ethtoolcoalesce-settings.yml playbook with the following content:

    ---
    - name: Configure an Ethernet connection with ethtool coalesce settings
      hosts: node.example.com
      become: true
      tasks:
      - include_role:
          name: linux-system-roles.network
    
        vars:
          network_connections:
            - name: enp1s0
              type: ethernet
              autoconnect: yes
              ip:
                address:
                  - 198.51.100.20/24
                  - 2001:db8:1::1/64
                gateway4: 198.51.100.254
                gateway6: 2001:db8:1::fffe
                dns:
                  - 198.51.100.200
                  - 2001:db8:1::ffbb
                dns_search:
                  - example.com
              ethtool:
                coalesce:
                  rx_frames: 128
                  tx_frames: 128
              state: up
  3. Run the playbook:

    • To connect as root user to the managed host, enter:

      # ansible-playbook -u root ~/configure-ethernet-device-with-ethtoolcoalesce-settings.yml
    • To connect as a user to the managed host, enter:

      # ansible-playbook -u user_name --ask-become-pass ~/configure-ethernet-device-with-ethtoolcoalesce-settings.yml

      The --ask-become-pass option makes sure that the ansible-playbook command prompts for the sudo password of the user defined in the -u user_name option.

    If you do not specify the -u user_name option, ansible-playbook connects to the managed host as the user that is currently logged in to the control node.

Additional resources

  • /usr/share/ansible/roles/rhel-system-roles.network/README.md
  • ansible-playbook(1) man page