The Linux kernel doesn’t consider routing to be a separate process, so it can eat lots of CPU capacity and still be at a load average of 0.

Load averages are calculated as the number of running and uninterruptible processes, sampled every 5 seconds, and then displayed as an exponentially decaying average, optionally per core (or SMT “core”). A process actively computing stuff is counted the same as a process that has an outstanding I/O request, which can be a source of excitement.

The act of routing packets (as opposed to working on a routing protocol exchange) is handled by the kernel, so it does not have a countable process identifier, so it does not count for load averages.

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