Chapter 10. Tuning the device driver and NIC

Procedure

1. Identify the driver:

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

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   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)

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   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>

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   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

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4. Unload the module:

   # modprobe -r e1000e

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   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

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6. Reactivate the network connections:

   # nmcli connection up <profile_name>

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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
   ...

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   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>

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