Michael Johnson 8b503d1eaf Add spec for SR-IOV in Octavia Amphora

This patch proposes a specification for adding SR-IOV VF port support to
Octavia Amphora load balancers.

Change-Id: I98961b162ae6811366bb036e6286f972908d785b

2023-12-05 15:50:16 +00:00

8.1 KiB

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Support SR-IOV network ports in Octavia

The maximum performance of Octavia Amphora based load balancers is often limited by the Software Defined Networking (SDN) used in the OpenStack deployment. There are users that want very high connection rates and high bandwidth through their load balancers.

This specification describes how we can add Single Root I/O Virtualization (SR-IOV) support to Octavia Amphora load balancers.

Problem description

Users would like to use SR-IOV VFs for the VIP and member ports on their Amphora based load balancers for improved maximum performance and reduced latency. Initial testing showed a 9% increase in bandwidth and a 70% drop in latency through the load balancer when using SR-IOV.
Users are overflowing tap interfaces with bursty "thundering herd" traffic such that packets are unable to make it into the Amphora instance.

Proposed change

Since Octavia hot plugs the network interfaces into the Amphora instances, the first work will be documenting how to configure nova to properly place the Amphorae on hosts with the required hardware and networks. There is some existing documentation for this in the nova guide, but we should summarize it with a focus on Amphora.

This documentation will include how to configure host aggregates, the compute flavor, and the Octavia flavor to properly schedule the Amphora instances.

In general, the SR-IOV ports will be handled the same as ports are with the AAP driver, including registering the VIP as an AAP address even though this is technically not required for SR-IOV ports, it will make sure the address is allocated in neutron. Only the base VRRP ports will allocate an SR-IOV VF as the AAP port will be "unbound" with a vnic_type of "normal".

The create load balancer flow creation will be enhanced to create the base VRRP port using an SR-IOV VF if the Octavia flavor has SRIOV_VIP set to true. If placement/nova scheduling fail to find an appropriate host or the SR-IOV VF port fails to plug into the Amphora, additional logging may be required, but the normal revert flows should continue to handle the error situation and mark the load balancer in provisioning status ERROR.

The building of the listener create and update flows will need to be updated to include extra tasks to configure nftables inside the Amphora to replace the functionality of the neutron security groups lost when using SR-IOV ports.

The Amphora agent will need to be enhanced for a new "security group" endpoint and to configure the Amphora nftables. The nftables rules will be added as stateless rules, meaning conntrack will not be enabled. The load balancing engines are already managing state for the flows, so there is no reason to also have state management in the firewall.

I am proposing we only support nftables inside the Amphora as most distributions are moving away from iptables towards nftables.

Alternatives

There are two obvious alternatives:

Do nothing and continue to rely on SDN performance.
Use provider networks to remove some of the overhead of the SDN.

It is not clear that SDN performance can improve to a level that would meet the needs of Octavia Amphora load balancers and provider networks still have some overhead and limitations depending on how they are implemented (tap interfaces, etc.)

Data model impact

The load balancer and member objects will be expanded to include the vnic type for the ports.

REST API impact

The Octavia API will be expanded to include the vnic type used for the VIP and member ports. The field with either be "normal" for OVS/OVN ports or "direct" for SR-IOV ports. This field with use the same terminology as neutron uses.

The Amphora API will need to be expanded to have a security group endpoint. This endpoint will accept POST calls that contain the: allowed_cidrs, protocol, and port information required to configure the appropriate nftable rules.

When this endpoint is called, the amphora agent will flush the current tables and build up a fresh table. There will be chains for the VIP, VRRP, and member ports. This will be implemented using the python nftables bindings.

Security impact

Neutron security groups do not work on SR-IOV ports, so the amphora agent will need to manage nftables for the SR-IOV ports.

There is no current use case where Octavia would need TRUST mode VFs, so this specification does not include any discussion of enabling TRUST on VFs used by the Octavia amphora driver. The amphora will treat TRUST VFs as if they were not TRUST enabled.

Notifications impact

None

Other end user impact

End users will need to select the appropriate Octavia flavor at load balancer creation time. They will also need to specify the proper network that matches the network(s) defined in the compute and Octavia flavors.

Performance Impact

This proposal is specifically about improving data plane performance.

I would expect little change to the provisioning time, or possibly a faster provisioning time, when using SR-IOV ports as it should require fewer API calls to Neutron.

Other deployer impact

If deployers want SR-IOV interface support at deployment time, they will need to configure the required compute host aggregates, compute flavors, and octavia flavor supporting the SR-IOV enabled hosts and networks.

We also recommend that the FDB L2 agent be enabled, when needed, so that virtual ports on the same compute host can communicate with the SR-IOV ports.

The Amphora images will now require the nftables and python3-nftables packages.

Developer impact

There should be minimal developer impact as it is enhancing existing flows.

Implementation

Assignee(s)

Primary assignee:: johnsom

Work Items

Document the required host aggregates, compute flavor, and Octavia flavor.
Update the load balancer "create" flow creation to use the SR-IOV tasks when creating the VRRP base ports.
Update the load balancer data model to store the port vnic type.
Expand the load balancer API to include the vnic type used for the VIP.
Update the listener create/update flows to add the extra tasks to configure the nftables inside the Amphora.
Add a security group endpoint to the Amphora agent to allow configuring and updating the nftables inside the Amphora.
Add any necessary logging and error handling should nova fail to attach SR-IOV ports.
Add the required unit and functional tests for the new code.
Add the required tempest tests to cover the usage scenarios (pending igb driver support in the PTI platforms)

Dependencies

None

Testing

Currently this feature cannot fully be tested in the OpenDev gates as it will require an SR-IOV capable nic in the test system.

There will be unit and function test coverage.

Recently qemu has added a virtual device, the "igb" device, that is capable of emulating an SR-IOV device. Versions of qemu and the associated libraries that include this new device are not yet shipping in any distribution supported by OpenStack.

When the "igb" device becomes available, we should be able to run scenario tests with SR-IOV VIP and member ports.

Performance testing will be out of scope because the OpenDev testing environment does not contain SR-IOV capable NICs and is not setup for data plane performance testing.

Documentation Impact

An administrative document will need to be created that describes the process required to setup a compute and octavia flavor for SR-IOV devices.

8.1 KiB Raw Blame History