public long reset() {
    long save = lastResetTime;
    lastResetTime = timeService.getTime();
    return lastResetTime - save;
  }
Compute and return the time in nanoseconds since the last reset or construction of this timer,
and reset the timer to the current {@link #getTime}.

@return time in nanoseconds since construction or last reset.
geode-core/src/main/java/org/apache/geode/internal/NanoTimer.java