For the process usage: we need to measure over a certain period of time,
then we can use the results. To avoid blocking, this does:
- after log is started, initialze the load counters, then one second later
add the results to the log
- after disarming: continue logging for one more second, then add the process
load to the log and stop logging.
- to avoid a delay, 'logger stop' will stop immediately and not log
postflight process usage.
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