Network interrupts, RSS, and kernel-bypass trade-offs

Receive Side Scaling — Parallelism for NICs

A single NIC has multiple RX queues — typically 4, 8, 16, or more depending on the model. Receive Side Scaling (RSS) is the mechanism that distributes incoming packets across these queues. The NIC hashes the packet flow tuple (typically 5-tuple: src/dst IP, src/dst port, protocol) and uses the hash to select an RX queue. Each queue is serviced by a different CPU core, enabling parallel packet processing. Without RSS, all incoming packets would go to one queue and one core would be the bottleneck. With RSS configured correctly across N queues and N cores, the NIC scales nearly linearly up to…