Why does the JVM show more latency for the same block of code after a busy spin pause?

Question

The code below demonstrates the problem unequivocally, which is:

The exact same block of code becomes slower after a busy spin pause.

Answer 1

You can probably not rely on the precision of any timer for the accuracy you seem to want, https://docs.oracle.com/javase/8/docs/api/java/lang/System.html#nanoTime-- states that

This method provides nanosecond precision, but not necessarily nanosecond resolution (that is, how frequently the value changes) - no guarantees are made except that the resolution is at least as good as that of currentTimeMillis().