Bug 1291352

+++ This bug was initially created as a clone of Bug #1153440 +++

Cloned from launchpad blueprint https://blueprints.launchpad.net/nova/+spec/libvirt-virtio-net-multiqueue.

Description:

Add supoort to enable the virtio-net multiqueue feature for guest
    instances.
    
    With virtio-net multiqueue enabled network performance can be scaled
    accross number of vCPUs, by transfering the packets through multiple virtqueue
    pairs at a time.
    
    Libvirt driver will set the number of queues equal to the number of guest VCPUs
    
    To control this feature, the following should be set in the flavour extra specs:
    
    hw:vif_multiqueue_enabled=true|disabled
    
    This setting can be overriden by the image metadata property if the feature
    is enabled in the extra specs:
    
    hw_vif_mutliqueue_enabled=true|false


Specification URL (additional information):

None

--- Additional comment from Vladik Romanovsky on 2015-09-08 12:41:53 EDT ---

The steps to enable the functionality differs from the original proposal.

Currently, the feature can only be enable or disabled for all vNICs of an instance.

A new parameter has been added to the image properties, for the users
to control the virtio-net multiqueue feature, to be able to enable or disable it.

    hw_vif_multiqueue_enabled=true|false  (default false)

The number of queues will match the number of vCPUs, defined for the instance.	

NOTE: Virtio-net multiqueue should be enabled in the guest OS manually, using	ethtool. For example:

    ethtool -L <NIC> combined #num_of_queues