Set custom Transmit Queue Length¶

The Transmit Queue Length (txqueuelen) is a TCP/IP stack network interface value that sets the number of packets allowed per kernel transmit queue of a network interface device.

By default, the txqueuelen value for TAP interfaces is set to 1000 in the MCP Build ID 2019.2.0 and to 10000 in the MCP 2019.2.3 maintenance update. You can also tune the txqueuelen value for TAP interfaces to optimize VM network performance under high load in certain scenarios.

To set a custom Transmit Queue Length value for TAP interfaces:

1. Log in to the Salt Master node.

2. Set the tap_custom_txqueuelen parameter for the OpenContrail or OVS compute nodes in one of the following files as required:

   • For the OpenContrail compute nodes, modify the cluster/<cluster_name>/opencontrail/networking/compute.yml file.
   • For the OVS compute nodes, modify the cluster/<cluster_name>/openstack/networking/compute.yml file.

   Example:

   linux:
     network:
       ...
       tap_custom_txqueuelen: 20000
   

3. Apply the change:

   salt '*' state.sls linux
   

4. Verify that the txqueuelen value has changed:

   1. Log in to the target node.
   2. Verify the output of the ifconfig <interface_name>. The txqueuelen value should equal the newly set value.