static int bucketMaxUs(int bucket) {
        return bucketMinUs(bucket + 1) - 1;
    }
@Test
    public void bucketMaxUs() {
        assertEquals(1, LatencyDistribution.bucketMaxUs(0));
        assertEquals(3, LatencyDistribution.bucketMaxUs(1));
        assertEquals(7, LatencyDistribution.bucketMaxUs(2));
        assertEquals(15, LatencyDistribution.bucketMaxUs(3));
        assertEquals(31, LatencyDistribution.bucketMaxUs(4));
        assertEquals(63, LatencyDistribution.bucketMaxUs(5));
    }