Logical Domains 1.2 Administration Guide

Using NIU Hybrid I/O

The virtual I/O framework implements a hybrid I/O model for improved functionality and performance. The hybrid I/O model combines direct and virtualized I/O to allow flexible deployment of I/O resources to virtual machines. It is particularly useful when direct I/O does not provide full capability for the virtual machine, or direct I/O is not persistently or consistently available to the virtual machine. This could be because of resource availability or virtual machine migration. The hybrid I/O architecture is well-suited to the Network Interface Unit (NIU), a network I/O interface integrated on chip, on Sun UltraSPARC T2–based platforms. This allows the dynamic assignment of Direct Memory Access (DMA) resources to virtual networking devices and, thereby, provides consistent performance to applications in the domain.

NIU hybrid I/O is available for Sun UltraSPARC T2–based platforms. This feature is enabled by an optional hybrid mode that provides for a virtual network (vnet) device where the DMA hardware resources are loaned to a vnet device in a guest domain for improved performance. In the hybrid mode, a vnet device in a guest domain can send and receive unicast traffic from an external network directly into the guest domain using the DMA hardware resources. The broadcast traffic and unicast traffic to the other guest domains in the same system continue to be sent using the virtual I/O communication mechanism.

Figure 7–6 Hybrid Virtual Networking

Diagram shows hybrid virtual networking as described in the text.

The hybrid mode applies only for the vnet devices that are associated with a virtual switch (vsw) configured to use an NIU network device. As the shareable DMA hardware resources are limited, up to only three vnet devices per vsw can have DMA hardware resources assigned at a given time. If more than three vnet devices have the hybrid mode enabled, the assignment is done on a first-come, first-served basis. As there are two NIU network devices in a system, there can be a total of six vnet devices on two different virtual switches with DMA hardware resources assigned.

Following are points you need to be aware of when using this feature:

ProcedureConfigure a Virtual Switch With an NIU Network Device

  1. For example, do the following to configure a virtual switch with a NIU network device.

    1. For example, determine an NIU network device.

      # grep nxge /etc/path_to_inst
      "/niu@80/network@0" 0 "nxge"
      "/niu@80/network@1" 1 "nxge"
    2. For example, configure a virtual switch.

      # ldm add-vsw net-dev=nxge0 primary-vsw0 primary

ProcedureEnable Hybrid Mode

  1. For example, enable a hybrid mode for a vnet device while it is being created.

    # ldm add-vnet mode=hybrid vnet01 primary-vsw0 ldom01

ProcedureDisable Hybrid Mode

  1. For example, disable hybrid mode for a vnet device.

    # ldm set-vnet mode= vnet01 ldom01