On the other hand if we're speaking historically then it was probably using a lot more than a hundredth of a percent of the address space. Or a billionth of the address space, depending on how we're counting.

It doesn't need to be free, but your address space use should be able to go a handful of bits above your physical memory without problems.

Even fully allocating all the page entries, with no large pages, on an architecture with 4KB pages, would only take 8MB to track a 4GB allocation.