Comment 8 for bug 1607961

Code block:

        # The CRUSH algorithm has a slight optimization for placement groups
        # with powers of 2 so find the nearest power of 2. If the nearest
        # power of 2 is more than 25% below the original value, the next
        # highest value is used. To do this, find the nearest power of 2 such
        # that 2^n <= num_pg, check to see if its within the 25% tolerance.
        exponent = math.floor(math.log(num_pg, 2))
        nearest = 2 ** exponent
        if (num_pg - nearest) > (num_pg * 0.25):
            # Choose the next highest power of 2 since the nearest is more
            # than 25% below the original value.
            return int(nearest * 2)
        else:
            return int(nearest)