I.4 Ring Buffer and txqueuelen Configuration (KVM)

To enable ring buffer configuration, use the KVM flavor and glance image. This increases the network throughout the VM.

1. Ensure that the ring buffer sizes and txqueuelen are set to max on all the ethernet devices on the host machine.
   1. Before setting ring buffer value for VMs, verify the pre-set maximum value on the hostmachine of RX and TX for all the interfaces using the following command:

      ethtool -g <interface-name>

      For example:

      /sbin/ethtool -g eth0
      /sbin/ethtool -g eth1
      /sbin/ethtool -g eth2
      /sbin/ethtool -g eth3
      Sample output of above command:
      ethtool -g eth0
      Ring parameters for eth0:
      Pre-set maximum:
      RX: 4096
      RX Mini: n/a
      RX Jumbo: n/a
      TX: 4096
      Current hardware settings:
      RX: 2080
      RX Mini: n/a
      RX Jumbo: n/a
      TX: 2080

   2. Create 30_ring_buff file by performing the following commands:

      [root@DSR-X9KVM-1 dispatcher.d]# cd /etc/NetworkManager/dispatcher.d/

      [root@DSR-X9KVM-1 dispatcher.d]# vim 30_ring_buff
      #!/bin/bash
      /sbin/ethtool -G ens1f0 rx 4078 tx 4078
      /sbin/ethtool -G ens1f1 rx 4078 tx 4078
      /sbin/ethtool -G ens1f2 rx 4078 tx 4078
      /sbin/ethtool -G ens1f3 rx 4078 tx 4078
      ifconfig ens1f0 txqueuelen 120000
      ifconfig ens1f1 txqueuelen 120000
      ifconfig ens1f2 txqueuelen 120000
      ifconfig ens1f3 txqueuelen 120000
      

      Note:

      The above content is an example file, which will change according to host parameters.
   3. Change the permission by performing the following command:

      [root@DSR-X9KVM-1 dispatcher.d]# chmod +x 30_ring_buff

   4. Use the pre-set maximum of RX and TX for each interface. Then, add the below script to file 30_ring_buff.

      /sbin/ethtool -G <interface-name> rx <RX-Preset Maximum> tx <TX-Preset
      Maximum>
      For example:
      #!/bin/bash
      /sbin/ethtool -G eth0 rx 4078 tx 4096
      /sbin/ethtool -G eth1 rx 4078 tx 4096
      /sbin/ethtool -G eth2 rx 4078 tx 4096
      /sbin/ethtool -G eth3 rx 4078 tx 4096

      Note:

      The above example files will change according to host parameters.
2. Restart all ethernet adapter eth0, eth1, eth2, and eth3 by performing the following command:

   systemctl restart NetworkManager

3. Verify that the ring buffer sizes are set to max on all the ethernet devices on the host machine by performing the following command:

   # ethtool -g <ethernet adapter>

   Verify the same for eth0, eth1, eth2, and eth3.

4. Run the following command to verify txqueue length for the ethernet adapter to a high value on the host machine that is added on all interfaces.

   # ifconfig <ethernet adapter>

   Note:

   These commands were tested on OL7.7 and OL8.9 KVM host machine and might vary for different versions.