At least some hardware provides the timestamp for you. Ideally if that's carried along with the packet, it measures the load on the whole system, so when you start dropping packets it's not just a function of network congestion but running out of cpu.
This would be a plus for a userspace router implementation, as presently in linux we timestamp on entry to the exit queue, not on all the overheads of routing lookup, and other processing from the read from the rx ring.
This would be a plus for a userspace router implementation, as presently in linux we timestamp on entry to the exit queue, not on all the overheads of routing lookup, and other processing from the read from the rx ring.