Absolutely right! Both Rust and Vale have their respective overheads. Fast mode is as fast as even C++, and strictly safer than e.g. the C++ + ASan approach, b

Absolutely right! Both Rust and Vale have their respective overheads. Fast mode is as fast as even C++, and strictly safer than e.g. the C++ + ASan approach, but Resilient Mode is where the speed+safety story gets interesting. I didn't have much opportunity to go into it in the article (it was already going on 15 pages, hah!) but there are some other aspects to Vale which should drastically cut down on reference-counting overhead: * Immutable region borrowing: we guarantee an entire is immutable, so all references into it are temporary and zero-cost, verified by the region borrow checker) * Bump-calling: a pure function can make its own new region which uses a bump-allocator for all allocations, and at the end we copy out the return value. * As mentioned, optimized ref-counting; we hope to reuse Lobster's algorithm, which removes 95% of ref counts. * Non-atomic ref-counting, because of the region isolation (like Rust's Rc, as opposed to its Arc), which is faster and more optimizable. I would of course agree that fast mode isn't for every use case; I would use it for a game or WASM, but not for a production server, where priorities are different. We think that the above four optimizations will give Resilient Mode speed on par with Rust and C++. Benchmarking will show us how close we can get!