Automatically assign logical cores to vNICs such that dedicated logical cores manage the incoming traffic to and outgoing traffic from vNICs.

With the N-VDS switch configured in the enhanced datapath mode, if a single logical core is associated to a vNIC, then that logical core processes bidirectional traffic coming into or going out of a vNIC. When multiple logical cores are configured, the host automatically determines which logical core must process a vNIC's traffic.

Assign logical cores to vNICs based on one of these parameters.
  • vNIC-count: Host assumes transmission of incoming or outgoing traffic for a vNIC direction requires same amount of the CPU resource. Each logical core is assigned the same number of vNICs based on the available pool of logical cores. It is the default mode. The vNIC-count mode is reliable, but is not optimal for an asymmetric traffic.

  • CPU-usage: Host predicts the CPU usage to transmit incoming or outgoing traffic at each vNIC direction by using internal statistics. Based on the usage of CPU to transmit traffic, host changes the logical core assignments to balance load among logical cores. The CPU usage mode is more optimal than vNIC-count, but unreliable when traffic is not steady.

In CPU usage mode, if the traffic transmitted changes frequently, then the predicted CPU resources required and vNIC assignment might also change frequently. Too frequent assignment changes might cause packet drops.

If the traffic patterns are symmetric among vNICs, the vNIC-count option provides reliable behavior, which is less vulnerable to frequent changes. However, if the traffic patterns are asymmetric, vNIC-count might result in packet drops since it does not distinguish the traffic difference among vNICs.

In vNIC-count mode, it is recommended to configure an appropriate number of logical cores so that each logical core is assigned to the same number of vNICs. If the number vNIC associated to each logical core is different, CPU assignment is unfair and performance is not deterministic.

When a vNIC is connected or disconnected or when a logical core is added or removed, hosts automatically detect the changes and rebalance.

Procedure

  • ♦ To switch from one mode to another mode, run the following command. 
    set ens lcore-assignment-mode <host-switch-name> <ens-lc-mode>

    Where, <ens-lc-mode> can be set to the mode vNIC-count or cpu-usage.

    vNIC-count is vNIC/Direction count-based logical core assignment.

    cpu-usage is CPU usage-based logical core assignment.