Just a related fact, traffic shaping requires timely access to the CPU, so latency is even more important than computational bandwidth, if a shaper fails to inject a packet into the underlaying layer in time, there is going to be a "(micro-)bubble" in the queue which will lead to less bandwidth efficiency and increased delay. My gut feeling is that it is this property that makes SQM/traffic-shapers quite sensitive to frequency-scaling/power-saving features, especially when it takes long to ramp the CPU back up again.