Periodic drops in throughput can be observed during checkpoints while running with an artificial workload and specific WiredTiger tuning parameters enabled.
I've attached diagnostic.tar.gz that shows this behavior. At around 2017-10-20T20:10:08.587Z the following command was executed:
After reaching steady state, we see the following:
Additionally, from perf, we can see that after making this parameter change, a single cpu core (12.5% of the total) is consistently fully utilized running eviction: