Chapter 10. Tuning the device driver and NIC

Procedure

1. Identify the driver:

   # ethtool -i enp0s31f6
   driver: e1000e
   version: ...
   firmware-version: ...
   ...

   Note that certain features can require a specific driver and firmware version.

2. Display the available parameters of the kernel module:

   # modinfo -p e1000e
   ...
   SmartPowerDownEnable:Enable PHY smart power down (array of int)
   parm:RxIntDelay:Receive Interrupt Delay (array of int)

   For further details on the parameters, see the kernel module’s documentation. For modules in RHEL, see the documentation in the /usr/share/doc/kernel-doc-<version>/Documentation/networking/device_drivers/ directory that is provided by the kernel-doc package.

3. Create the /etc/modprobe.d/nic-parameters.conf file and specify the parameters for the module:

   options <module_name> <parameter1>=<value> <parameter2>=<value>

   For example, to enable the port power saving mechanism and set the generation of receive interrupts to 4 units, enter:

   options e1000e SmartPowerDownEnable=1 RxIntDelay=4

4. Unload the module:

   # modprobe -r e1000e

   Warning

   Unloading a module that an active network interface uses immediately terminates the connection and you can lock yourself out of the server.

5. Load the module:

   # modprobe e1000e

6. Reactivate the network connections:

   # nmcli connection up <profile_name>

Verification

1. Display the kernel messages:

   # dmesg
   ...
   [35309.225765] e1000e 0000:00:1f.6: Transmit Interrupt Delay set to 16
   [35309.225769] e1000e 0000:00:1f.6: PHY Smart Power Down Enabled
   ...

   Note that not all modules log parameter settings to the kernel ring buffer.

2. Certain kernel modules create files for each module parameter in the /sys/module/<driver>/parameters/ directory. Each of these files contain the current value of this parameter. You can display these files to verify a setting:

   # cat /sys/module/<driver_name>/parameters/<parameter_name>