Port rx queues that have not been statically assigned to PMDs are currently assigned based on periodically sampled load measurements.
The assignment is performed at specific instances – port addition, port deletion, upon reassignment request via CLI etc.
It is quite possible that the traffic pattern may change after the assignment. This could lead to unbalanced load distribution among the PMDs, resulting in lower throughput.
The proposed solution is to have each PMD measure the processing load for each of its associated queues (based on processing and total cycles) every 10 seconds. If the aggregated PMD load exceeds a configured threshold for 6 consecutive intervals and if there are receive packet drops at the NIC the PMD considers itself to be overloaded.
If any PMD considers itself to be overloaded, a dry-run of the PMD assignment algorithm is performed by OVS main thread. The dry-run does NOT change the existing queue to PMD assignments.
If the resultant mapping of dry-run indicates an improved distribution of the load the actual reassignment will be performed.
The automatic rebalancing will be disabled by default and has to be enabled via configuration option. Load thresholds, improvement factor etc will also be configurable
