By default many Linux network interface card drivers set their SMP affinity mask to either all zeroes or all ones (“ff” — the length of the mask 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. (more…)