Chapter 30. Configuring ethtool settings in NetworkManager connection profiles NetworkManager can configure certain network driver and hardware settings persistently. Compared to using the ethtool utility to manage these settings, this has the benefit of not losing the settings after a reboot. You can set the following ethtool settings in NetworkManager connection profiles: Offload features Network interface controllers can use the TCP offload engine (TOE) to offload processing certain operations to the network controller. This improves the network throughput. Interrupt coalesce settings By 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. Ring buffers These buffers store incoming and outgoing network packets. You can increase the ring buffer sizes to reduce a high packet drop rate. Channel settings A network interface manages its associated number of channels along with hardware settings and network drivers. All devices associated with a network interface communicate with each other through interrupt requests (IRQ). Each device queue holds pending IRQ and communicates with each other over a data line known as channel. Types of queues are associated with specific channel types. These channel types include: rx for receiving queues tx for transmit queues other for link interrupts or single root input/output virtualization (SR-IOV) coordination combined for hardware capacity-based multipurpose channels 30.1. Configuring an ethtool offload feature by using nmcli You can use NetworkManager to enable and disable ethtool offload features in a connection profile. Procedure For example, to enable the RX offload feature and disable TX offload in the enp1s0 connection profile, enter: This command explicitly enables RX offload and disables TX offload. To remove the setting of an offload feature that you previously enabled or disabled, set the feature's parameter to a null value. For example, to remove the configuration for TX offload, enter: Reactivate the network profile: Verification Use the ethtool -k command to display the current offload features of a network device: Additional resources nm-settings-nmcli(5) man page on your system 30.2. Configuring an ethtool offload feature by using the network RHEL system role Network interface controllers can use the TCP offload engine (TOE) to offload processing certain operations to the network controller. This improves the network throughput. You configure offload features in the connection profile of the network interface. By using Ansible and the network RHEL system role, you can automate this process and remotely configure connection profiles on the hosts defined in a playbook. Warning You cannot use the network RHEL system role to update only specific values in an existing connection profile. The role ensures that a connection profile exactly matches the settings in a playbook. If a connection profile with the same name already exists, the role applies the settings from the playbook and resets all other settings in the profile to their defaults. To prevent resetting values, always specify the whole configuration of the network connection profile in the playbook, including the settings that you do not want to change. Prerequisites You have prepared the control node and the managed nodes You are logged in to the control node as a user who can run playbooks on the managed nodes. The account you use to connect to the managed nodes has sudo permissions on them. Procedure Create a playbook file, for example ~/playbook.yml , with the following content: --- - name: Configure the network hosts: managed-node-01.example.com tasks: - name: Ethernet connection profile with dynamic IP address settings and offload features ansible.builtin.include_role: name: rhel-system-roles.network vars: network_connections: - name: enp1s0 type: ethernet autoconnect: yes ip: dhcp4: yes auto6: yes ethtool: features: gro: no gso: yes tx_sctp_segmentation: no state: up The settings specified in the example playbook include the following: gro: no Disables Generic receive offload (GRO). gso: yes Enables Generic segmentation offload (GSO). tx_sctp_segmentation: no Disables TX stream control transmission protocol (SCTP) segmentation. For details about all variables used in the playbook, see the /usr/share/ansible/roles/rhel-system-roles.network/README.md file on the control node. Validate the playbook syntax: Note that this command only validates the syntax and does not protect against a wrong but valid configuration. Run the playbook: Verification Query the Ansible facts of the managed node and verify the offload settings: Additional resources /usr/share/ansible/roles/rhel-system-roles.network/README.md file /usr/share/doc/rhel-system-roles/network/ directory 30.3. Configuring an ethtool coalesce settings by using nmcli You can use NetworkManager to set ethtool coalesce settings in connection profiles. Procedure For example, to set the maximum number of received packets to delay to 128 in the enp1s0 connection profile, enter: To remove a coalesce setting, set it to a null value. For example, to remove the ethtool.coalesce-rx-frames setting, enter: To reactivate the network profile: Verification Use the ethtool -c command to display the current offload features of a network device: Additional resources nm-settings-nmcli(5) man page on your system 30.4. Configuring an ethtool coalesce settings by using the network RHEL system role By 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. You configure coalesce settings in the connection profile of the network interface. By using Ansible and the network RHEL role, you can automate this process and remotely configure connection profiles on the hosts defined in a playbook. Warning You cannot use the network RHEL system role to update only specific values in an existing connection profile. The role ensures that a connection profile exactly matches the settings in a playbook. If a connection profile with the same name already exists, the role applies the settings from the playbook and resets all other settings in the profile to their defaults. To prevent resetting values, always specify the whole configuration of the network connection profile in the playbook, including the settings that you do not want to change. Prerequisites You have prepared the control node and the managed nodes You are logged in to the control node as a user who can run playbooks on the managed nodes. The account you use to connect to the managed nodes has sudo permissions on them. Procedure Create a playbook file, for example ~/playbook.yml , with the following content: --- - name: Configure the network hosts: managed-node-01.example.com tasks: - name: Ethernet connection profile with dynamic IP address settings and coalesce settings ansible.builtin.include_role: name: rhel-system-roles.network vars: network_connections: - name: enp1s0 type: ethernet autoconnect: yes ip: dhcp4: yes auto6: yes ethtool: coalesce: rx_frames: 128 tx_frames: 128 state: up The settings specified in the example playbook include the following: rx_frames: <value> Sets the number of RX frames. gso: <value> Sets the number of TX frames. For details about all variables used in the playbook, see the /usr/share/ansible/roles/rhel-system-roles.network/README.md file on the control node. Validate the playbook syntax: Note that this command only validates the syntax and does not protect against a wrong but valid configuration. Run the playbook: Verification Display the current offload features of the network device: Additional resources /usr/share/ansible/roles/rhel-system-roles.network/README.md file /usr/share/doc/rhel-system-roles/network/ directory 30.5. Increasing the ring buffer size to reduce a high packet drop rate by using nmcli Increase the size of an Ethernet device's ring buffers if the packet drop rate causes applications to report a loss of data, timeouts, or other issues. Receive ring buffers are shared between the device driver and network interface controller (NIC). The card assigns a transmit (TX) and receive (RX) ring buffer. As the name implies, the ring buffer is a circular buffer where an overflow overwrites existing data. There are two ways to move data from the NIC to the kernel, hardware interrupts and software interrupts, also called SoftIRQs. The kernel uses the RX ring buffer to store incoming packets until the device driver can process them. The device driver drains the RX ring, typically by using SoftIRQs, which puts the incoming packets into a kernel data structure called an sk_buff or skb to begin its journey through the kernel and up to the application that owns the relevant socket. The kernel uses the TX ring buffer to hold outgoing packets which should be sent to the network. These ring buffers reside at the bottom of the stack and are a crucial point at which packet drop can occur, which in turn will adversely affect network performance. Procedure Display the packet drop statistics of the interface: 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. Display the maximum ring buffer sizes: 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 steps. Identify the NetworkManager connection profile that uses the interface: Update the connection profile, and increase the ring buffers: To increase the RX ring buffer, enter: To increase the TX ring buffer, enter: Reload the NetworkManager connection: Important Depending on the driver your NIC uses, changing in the ring buffer can shortly interrupt the network connection. Additional resources ifconfig and ip commands report packet drops (Red Hat Knowledgebase) Should I be concerned about a 0.05% packet drop rate? (Red Hat Knowledgebase) ethtool(8) man page on your system 30.6. Increasing the ring buffer size to reduce a high packet drop rate by using the network RHEL system role Increase the size of an Ethernet device's ring buffers if the packet drop rate causes applications to report a loss of data, timeouts, or other issues. Ring buffers are circular buffers where an overflow overwrites existing data. The network card assigns a transmit (TX) and receive (RX) ring buffer. Receive ring buffers are shared between the device driver and the network interface controller (NIC). Data can move from NIC to the kernel through either hardware interrupts or software interrupts, also called SoftIRQs. The kernel uses the RX ring buffer to store incoming packets until the device driver can process them. The device driver drains the RX ring, typically by using SoftIRQs, which puts the incoming packets into a kernel data structure called an sk_buff or skb to begin its journey through the kernel and up to the application that owns the relevant socket. The kernel uses the TX ring buffer to hold outgoing packets which should be sent to the network. These ring buffers reside at the bottom of the stack and are a crucial point at which packet drop can occur, which in turn will adversely affect network performance. You configure ring buffer settings in the NetworkManager connection profiles. By using Ansible and the network RHEL system role, you can automate this process and remotely configure connection profiles on the hosts defined in a playbook. Warning You cannot use the network RHEL system role to update only specific values in an existing connection profile. The role ensures that a connection profile exactly matches the settings in a playbook. If a connection profile with the same name already exists, the role applies the settings from the playbook and resets all other settings in the profile to their defaults. To prevent resetting values, always specify the whole configuration of the network connection profile in the playbook, including the settings that you do not want to change. Prerequisites You have prepared the control node and the managed nodes You are logged in to the control node as a user who can run playbooks on the managed nodes. The account you use to connect to the managed nodes has sudo permissions on them. You know the maximum ring buffer sizes that the device supports. Procedure Create a playbook file, for example ~/playbook.yml , with the following content: --- - name: Configure the network hosts: managed-node-01.example.com tasks: - name: Ethernet connection profile with dynamic IP address setting and increased ring buffer sizes ansible.builtin.include_role: name: rhel-system-roles.network vars: network_connections: - name: enp1s0 type: ethernet autoconnect: yes ip: dhcp4: yes auto6: yes ethtool: ring: rx: 4096 tx: 4096 state: up The settings specified in the example playbook include the following: rx: <value> Sets the maximum number of received ring buffer entries. tx: <value> Sets the maximum number of transmitted ring buffer entries. For details about all variables used in the playbook, see the /usr/share/ansible/roles/rhel-system-roles.network/README.md file on the control node. Validate the playbook syntax: Note that this command only validates the syntax and does not protect against a wrong but valid configuration. Run the playbook: Verification Display the maximum ring buffer sizes: Additional resources /usr/share/ansible/roles/rhel-system-roles.network/README.md file /usr/share/doc/rhel-system-roles/network/ directory 30.7. Configuring an ethtool channels settings by using nmcli By using NetworkManager, you can manage network devices and connections. The ethtool utility manages the link speed and related settings of a network interface card. ethtool handles IRQ based communication with associated devices to manage related channels settings in connection profiles. Procedure Display the channels associated with a network device: Update the channel settings of a network interface: Reactivate the network profile: Verification Check the updated channel settings associated with the network device: Additional resources nmcli(5) man page on your system

Commands:
nmcli con modify enp1s0 ethtool.feature-rx on ethtool.feature-tx off
nmcli con modify enp1s0 ethtool.feature-tx ""
nmcli connection up enp1s0
ethtool -k network_device
--- - name: Configure the network hosts: managed-node-01.example.com tasks: - name: Ethernet connection profile with dynamic IP address settings and offload features ansible.builtin.include_role: name: rhel-system-roles.network vars: network_connections: - name: enp1s0 type: ethernet autoconnect: yes ip: dhcp4: yes auto6: yes ethtool: features: gro: no gso: yes tx_sctp_segmentation: no state: up
ansible-playbook --syntax-check ~/playbook.yml
ansible-playbook ~/playbook.yml
ansible managed-node-01.example.com -m ansible.builtin.setup "ansible_enp1s0": { "active": true, "device": "enp1s0", "features": { "rx_gro_hw": "off, "tx_gso_list": "on, "tx_sctp_segmentation": "off", }
nmcli connection modify enp1s0 ethtool.coalesce-rx-frames 128
nmcli connection modify enp1s0 ethtool.coalesce-rx-frames ""
nmcli connection up enp1s0
ethtool -c network_device
--- - name: Configure the network hosts: managed-node-01.example.com tasks: - name: Ethernet connection profile with dynamic IP address settings and coalesce settings ansible.builtin.include_role: name: rhel-system-roles.network vars: network_connections: - name: enp1s0 type: ethernet autoconnect: yes ip: dhcp4: yes auto6: yes ethtool: coalesce: rx_frames: 128 tx_frames: 128 state: up
ansible-playbook --syntax-check ~/playbook.yml
ansible-playbook ~/playbook.yml
ansible managed-node-01.example.com -m command -a 'ethtool -c enp1s0' managed-node-01.example.com | CHANGED | rc=0 >> rx-frames: 128 tx-frames: 128
ethtool -S enp1s0 rx_queue_0_drops: 97326 rx_queue_1_drops: 63783
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
nmcli connection show NAME UUID TYPE DEVICE Example-Connection a5eb6490-cc20-3668-81f8-0314a27f3f75 ethernet enp1s0
nmcli connection modify Example-Connection ethtool.ring-rx 4096
nmcli connection modify Example-Connection ethtool.ring-tx 4096
nmcli connection up Example-Connection
--- - name: Configure the network hosts: managed-node-01.example.com tasks: - name: Ethernet connection profile with dynamic IP address setting and increased ring buffer sizes ansible.builtin.include_role: name: rhel-system-roles.network vars: network_connections: - name: enp1s0 type: ethernet autoconnect: yes ip: dhcp4: yes auto6: yes ethtool: ring: rx: 4096 tx: 4096 state: up
ansible-playbook --syntax-check ~/playbook.yml
ansible-playbook ~/playbook.yml
ansible managed-node-01.example.com -m command -a 'ethtool -g enp1s0' managed-node-01.example.com | CHANGED | rc=0 >> Current hardware settings: RX: 4096 RX Mini: 0 RX Jumbo: 0 TX: 4096
ethtool --show-channels enp1s0 Channel parameters for enp1s0 : Pre-set maximums: RX: 4 TX: 3 Other: 10 Combined: 63 Current hardware settings: RX: 1 TX: 1 Other: 1 Combined: 1
nmcli connection modify enp1s0 ethtool.channels-rx 4 ethtool.channels-tx 3 ethtools.channels-other 9 ethtool.channels-combined 50
nmcli connection up enp1s0
ethtool --show-channels enp1s0 Channel parameters for enp1s0 : Pre-set maximums: RX: 4 TX: 3 Other: 10 Combined: 63 Current hardware settings: RX: 4 TX: 3 Other: 9 Combined: 50