8.9. Accelerated RFS

Accelerated RFS boosts the speed of RFS by adding hardware assistance. Like RFS, packets are forwarded based on the location of the application consuming the packet. Unlike traditional RFS, however, packets are sent directly to a CPU that is local to the thread consuming the data: either the CPU that is executing the application, or a CPU local to that CPU in the cache hierarchy.
Accelerated RFS is only available if the following conditions are met:
  • Accelerated RFS must be supported by the network interface card. Accelerated RFS is supported by cards that export the ndo_rx_flow_steer() netdevice function.
  • ntuple filtering must be enabled.
Once these conditions are met, CPU to queue mapping is deduced automatically based on traditional RFS configuration. That is, CPU to queue mapping is deduced based on the IRQ affinities configured by the driver for each receive queue. Refer to Section 8.8, “Receive Flow Steering (RFS)” for details on configuring traditional RFS.
Red Hat recommends using accelerated RFS wherever using RFS is appropriate and the network interface card supports hardware acceleration.