SplitRX mode

SplitRx mode, a new feature in ESXi 5.0, uses multiple physical CPUs to process network packets received in a single network queue. This feature can significantly improve network performance for certain workloads.

Workloads like: ?

• Multiple virtual machines on one ESXi host all receiving multicast traffic from the same source. (SplitRx mode will typically improve throughput and CPU efficiency for these workloads.) ?
• Traffic via the vNetwork Appliance (DVFilter) API between two virtual machines on the same ESXi host. (SplitRx mode will typically improve throughput and maximum packet rates for these workloads.)

This feature, which is supported only for VMXNET3 virtual network adapters, is individually configured for each virtual NIC using the ethernetX.emuRxMode variable in each virtual machine’s .vmx file (where X is replaced with the network adapter’s ID).

The possible values for this variable are: ? ethernetX.emuRxMode = “0″
This value disables splitRx mode for ethernetX. ?

ethernetX.emuRxMode = “1″
This value enables splitRx mode for ethernetX.

To change this variable through the vSphere Client:

1 Select the virtual machine you wish to change, then click Edit virtual machine settings.
2 Under the Options tab, select General, then click Configuration Parameters.
3 Look for ethernetX.emuRxMode (where X is the number of the desired NIC). If the variable isn’t present, click Add Row and enter it as a new variable.
4 Click on the value to be changed and configure it as you wish. The change will not take effect until the virtual machine has been restarted.

Thanks to VMware, Information is from the white paper provided by VMware.