This script sets the CPU affinity for network interfaces and interface queues across all the CPUs in an efficient manner.
By default many drivers set their SMP affinity mask to either zero or all ones ("ff" -- length depends on the number of CPUs on the system). The former results in all queues and interfaces running on CPU ID 0, which can become a performance bottleneck due to insufficient computing power. The latter results in all queues and interfaces being scheduled on multiple CPUs, which can become a performance bottleneck due to increased CPU memory cache misses.
Some drivers create multiple queues each with its own IRQ, which then can each be assigned to its own CPU. Drivers appear to create as many queues as there are CPUs, unless the NIC hardware capabilities limit the total to a lower number.
Some drivers create separate transmit (TX) and receive (RX) queues. For optimal cache hits, the TX and RX sides of a given queue must be scheduled on the same CPU.
Even without multiple queues, a performance boost can be attained on multihomed hosts and when using bonded interfaces by assigning each NIC to a separate CPU.
Only queues matching the naming schemes implemented in the following drivers are assigned:
- e1000e
- igb
- sfc
- xen_netfront
Please send pull requests for additional naming schemes.
Signed releases can be downloaded from my software distribution server: