presto-main/src/main/java/io/prestosql/operator/OperationTimer.java/OperationTimer/recordOperationComplete
class OperationTimer:    void recordOperationComplete(OperationTiming operationTiming)
    {
        requireNonNull(operationTiming, "operationTiming is null");
        checkState(!finished, "timer is finished");

        long intervalCpuEnd = trackOperationCpuTime ? currentThreadCpuTime() : 0;
        long intervalWallEnd = System.nanoTime();

        long operationWallNanos = nanosBetween(intervalWallStart, intervalWallEnd);
        long operationCpuNanos = trackOperationCpuTime ? nanosBetween(intervalCpuStart, intervalCpuEnd) : 0;
        operationTiming.record(operationWallNanos, operationCpuNanos);

        intervalWallStart = intervalWallEnd;
        intervalCpuStart = intervalCpuEnd;
    }