Virtual Machine Device Queues

Boost network I/O to meet the demands of consolidated virtual workloads. Multiple virtual machines (VMs) introduce heavy traffic-management demands that servers must meet in order to ensure scalability and get the full value of virtualization.

Virtual Machine Device Queues (VMDQ), a component of Intel® Virtualization Technology (Intel® VT) for Connectivity (Intel® VT-c), optimizes the processing of VM data traffic to improve CPU utilization and bandwidth.

VMDQ Enhances Virtualized Traffic Management

As the number of VMs on a server increases, so does the amount and complexity of traffic. VMDQ manages the VMs' data traffic efficiently in order to reduce the I/O bottleneck in the system:

  • Throughput: Provides an alternative to VMM-based packet sorting, to ease throughput limitations
  • Scalability: Creates parallel data I/O paths in the network I/O silicon to avoid performance degradation as the number of VMs increases
  • Capacity: Liberates CPU cycles otherwise consumed by packet sorting, making them available to applications

These advances promise to increase server-consolidation ratios, adding to the cost savings associated with virtualization solutions.

Solutions for Virtualized I/O Challenges

VMDQ offloads the sorting burden from the VMM to the network controller, to accelerate network I/O throughput.

Together, these capabilities of VMDQ improve the robustness of network connectivity to provide better traffic management capabilities to the VM data traffic:

  • Hardware-based prioritization and queuing reduces the burden on the VMM by allocating individual VMs' data to respective hardware queues to improve overall efficiency.
  • Additional data queues make the data path to the network interface parallel rather than the traditional serial, per-packet model, allowing VMs to more efficiently share network ports.
  • Packet sorting by the network interface hardware for incoming data removes that burden from the VMM software, avoiding I/O processing bottlenecks.
  • Round-robin queue servicing by the network interface hardware improves transmit fairness and avoids head-of-line blocking among VMs, better enabling bandwidth efficiency and quality of service.

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