presto-main/src/main/java/io/prestosql/execution/StageStateMachine.java/StageStateMachine/recordGetSplitTime
class StageStateMachine:    public void recordGetSplitTime(long startNanos)
    {
        long elapsedNanos = System.nanoTime() - startNanos;
        getSplitDistribution.add(elapsedNanos);
        scheduledStats.getGetSplitTime().add(elapsedNanos, NANOSECONDS);
    }