Hi everyone.  I'd like to add request duration to our HTTP access log, and found the "record-request-start-time" setting in the documentation.

The documentation says "This has a small but measurable performance impact."  But is that really true?  From what I can see in the code, all it's doing is calling System.nanoTime().

Chasing this led me to a lot of Google searching on nanoTime() itself, and its performance.  There's a lot of out-dated information out there, especially with regard to Linux.  From what I can see in the Java source, it's using clock_gettime(CLOCK_MONOTONIC), and various sources say this is plenty fast: