Investigate CPU load

[DavidVorick]

Running the test at full speed results in the CPU being under continuous load. This library is supposed to be permanently I/O bound, we'll have to figure out what is burning all the cpu cycles.

[ChrisSchinnerl]

It seems like most of the cpu load comes from calling Blake2b. No test or benchmark maxes out the CPU load except for TestSilo which continuously generates random numbers within 250 threads.