I don't think you quite understand the problem... The cost isn't in literally freeing objects but in doing the mark/{sweep,copy}. So Cheney's collection is not

I don't think you quite understand the problem... The cost isn't in literally freeing objects but in doing the mark/{sweep,copy}. So Cheney's collection is not equivalent to decrementing the stack pointer. The only special things about the stack per se are a) arena[0] allocation and b) special ISA and OS support. When people say "stack allocation" the important points are (a) as well as c) static lifetime analysis. These are different concepts: Rust, for example, achieves (c) on the heap as well as the native stack. [0] I.e., three-pointer, although for the stack the OS manages at least one of them