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Multiqueue Virtio Interfaces in Virtual Machines

Contrail 3.2 adds support for multiqueue for the DPDK-based vrouter.

Contrail 3.1 supports multiqueue virtio interfaces for Ubuntu kernel-based router, only.

Multiqueue Virtio Overview

OpenStack Liberty supports the ability to create VMs with multiple queues on their virtio interfaces. Virtio is a Linux platform for I/O virtualization, providing a common set of I/O virtualization drivers. Multiqueue virtio is an approach that enables the processing of packet sending and receiving to be scaled to the number of available virtual CPUs (vCPUs) of a guest, through the use of multiple queues.

Requirements and Setup for Multiqueue Virtio Interfaces

To use multiqueue virtio interfaces, ensure your system meets the following requirements:

  • The OpenStack version must be Liberty or greater.

  • The maximum number of queues in the VM interface is set to the same value as the number of vCPUs in the guest.

  • The VM image metadata property is set to enable multiple queues inside the VM.

Setting Virtual Machine Metadata for Multiple Queues

Use the following command on the OpenStack node to enable multiple queues on a VM:

After the VM is spawned, use the following command on the virtio interface in the guest to enable multiple queues inside the VM:

ethtool –L <interface_name> combined <#queues>

Packets will now be forwarded on all queues in the VM to and from the vRouter running on the host.


Multiple queues in the VM are only supported with the kernel mode vRouter in Contrail 3.1.

Contrail 3.2 adds support for multiple queues with the DPDK-based vrouter, using OpenStack Mitaka. The DPDK vrouter has the same setup requirements as the kernel mode vrouter. However, in the ethtool –L setup command, the number of queues cannot be higher than the number of CPU cores assigned to vrouter in the testbed file.