Anthony Atkielski wrote:
Exactly ... but that's the magic of the variable address scheme. You only
have to allocate disparate chunks in a fixed address scheme because the size
of each chunk is limited by the length of an address field. But if the
address field is variable, you can make any chunk as big as you want. If
you have addresses of 4739124xx initially (Metropolis only had a few
machines at first), and you run out of addresses after 473912498, you just
make 473912499 point to "more addresses for Metropolis," and start
allocating, say 4739124990001 through 4739124999998 (you always leave at
least one slot empty so that it can point to "more addresses").
Seems like that's very inefficient. You're building a tree. You make the
tree deeper in places where you have more nodes.
Even with forward-looking allocations, the tree is going to lopside
toward a linear organization, and need to be rebalanced.
(e.g., renumbered).
No matter how conservative they are, the finite length of the address field
will eventually cause problems, and much sooner than anyone thinks.
And variable length addrs. will cause problems eventually too, but it'll
be harder to explain why.
Joe