I want to count the time elapsed between two events in nanoseconds. To do that, I can use System.nanoTime() as mentioned here. The problem is that the two events are happening in different threads.
Since nanoTime() doesn't return an absolute timestamp but instead can only be used to calculate time differences, I'd like to know if the values I get on the two different threads are consistent with the physical time elapsed between the two events.
It's supposed to be, but due to buggy kernels or hardware, the answer can be no, at least in some environments.
来源：https://stackoverflow.com/questions/2688099/is-system-nanotime-consistent-across-threads