[chrchang523]

Incidentally, you can choose to bump in both directions. It's more complicated (you need to keep track of which end you allocated each data structure on), but in exchange, the allocator becomes sufficient for many more use cases.

Given a choice, the OP implies that you should position small-but-numerous allocations next to the top, and larger infrequent allocations next to the bottom.

[dev_dwarf]

This sounds like it would make the alloc logic much more complicated and branch-y, defeating the purpose of bumping down anyway, unless your implying some compile-time way to do this.

[chrchang523]

No, the idea is that you manually make some allocations downward from the top and some allocations upward from the bottom. The bumping code is as simple as in the unidirectional case.

The tricky part is choosing in a way that puts you noticeably ahead of the unidirectional allocator re: what problems you can solve, without putting excessive mental load on yourself. I've found a pattern of "long-lived allocations on one end, short-lived allocations on the other" to work well here (which, yes, doesn't always coincide with the numerous vs. infrequent axis mentioned in my previous comment).