Note sure if I fully grasped your quesiton but here it goes. Light threads and stackfull coroutines require stack allocation. That is their cost and it is unbe

Note sure if I fully grasped your quesiton but here it goes. Light threads and stackfull coroutines require stack allocation. That is their cost and it is unbearable for system-level language priding itself in zero-cost abstractions. Eg. AFAIK, it's the main reason that is making Go calling C code slow. Also, (again AFAIK) Rust stackless coroutines and futures compile down to state machines, so I don't understand the "lexical closure overhead". There's nothing forcing futures to be "running on a single-core cpu" in Rust, since Rust can reason about thread-safety. Personally, after couple of months of using JS at dayjob, I very dislike JS (as I thought I would), but I love coroutines/yield. I think they will be glorious in Rust: they will allow writting reasonably nice code with an amazing performance.