hw_vif_mutliqueue_enabled is not the right spelling. Change-Id: I0fe4734888b734ac5962a530e2429d94aa4594d1 Closes-bug: #1767267
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Open vSwitch with DPDK datapath
This page serves as a guide for how to use the OVS with DPDK datapath functionality available in the Networking service as of the Mitaka release.
The basics
Open vSwitch (OVS) provides support for a Data Plane Development Kit
(DPDK) datapath since OVS 2.2, and a DPDK-backed vhost-user
virtual interface since OVS 2.4. The DPDK datapath provides lower
latency and higher performance than the standard kernel OVS datapath,
while DPDK-backed vhost-user
interfaces can connect guests
to this datapath. For more information on DPDK, refer to the DPDK website.
OVS with DPDK, or OVS-DPDK, can be used to provide high-performance networking between instances on OpenStack compute nodes.
Prerequisites
Using DPDK in OVS requires the following minimum software versions:
- OVS 2.4
- DPDK 2.0
- QEMU 2.1.0
- libvirt 1.2.13
Support of vhost-user
multiqueue that enables use of
multiqueue with virtio-net
and igb_uio
is
available if the following newer versions are used:
- OVS 2.5
- DPDK 2.2
- QEMU 2.5
- libvirt 1.2.17
In both cases, install and configure Open vSwitch with DPDK support
for each node. For more information, see the OVS-DPDK
installation guide (select an appropriate OVS version in the Branch
drop-down
menu).
/contributor/internals/ovs_vhostuser
for configuration
of neutron OVS agent.
In case you wish to configure multiqueue, see the OVS configuration chapter on vhost-user in QEMU documentation.
The technical background of multiqueue is explained in the corresponding blueprint.
Additionally, OpenStack supports vhost-user
reconnect
feature starting from the Ocata release, as implementation of fix for bug 1604924.
Starting from OpenStack Ocata release this feature is used without any
configuration necessary in case the following minimum software versions
are used:
- OVS 2.6
- DPDK 16.07
- QEMU 2.7
The support of this feature is not yet present in ML2 OVN and ODL mechanism drivers.
Using vhost-user interfaces
Once OVS and neutron are correctly configured with DPDK support,
vhost-user
interfaces are completely transparent to the
guest (except in case of multiqueue configuration described below).
However, guests must request huge pages. This can be done through
flavors. For example:
$ openstack flavor set m1.large --property hw:mem_page_size=large
For more information about the syntax for
hw:mem_page_size
, refer to the Flavors
guide.
Note
vhost-user
requires file descriptor-backed shared
memory. Currently, the only way to request this is by requesting large
pages. This is why instances spawned on hosts with OVS-DPDK must request
large pages. The aggregate flavor affinity filter can be used to
associate flavors with large page support to hosts with OVS-DPDK
support.
Create and add vhost-user
network interfaces to
instances in the same fashion as conventional interfaces. These
interfaces can use the kernel virtio-net
driver or a
DPDK-compatible driver in the guest
$ openstack server create --nic net-id=$net_id ... testserver
Using vhost-user multiqueue
To use this feature, the following should be set in the flavor extra specs (flavor keys):
$ openstack flavor set $m1.large --property hw:vif_multiqueue_enabled=true
This setting can be overridden by the image metadata property if the feature is enabled in the extra specs:
$ openstack image set --property hw_vif_multiqueue_enabled=true IMAGE_NAME
Support of virtio-net
multiqueue needs to be present in
kernel of guest VM and is available starting from Linux kernel 3.8.
Check pre-set maximum for number of combined channels in channel configuration. Configuration of OVS and flavor done successfully should result in maximum being more than '1'):
$ ethtool -l INTERFACE_NAME
To increase number of current combined channels run following command in guest VM:
$ ethtool -L INTERFACE_NAME combined QUEUES_NR
The number of queues should typically match the number of vCPUs defined for the instance. In newer kernel versions this is configured automatically.
Known limitations
- This feature is only supported when using the libvirt compute driver, and the KVM/QEMU hypervisor.
- Huge pages are required for each instance running on hosts with OVS-DPDK. If huge pages are not present in the guest, the interface will appear but will not function.
- Expect performance degradation of services using tap devices: these devices do not support DPDK. Example services include DVR, FWaaS, or LBaaS.