Hacker News Reader

I think more importantly it is reference counting across threads, meaning mutexes and breaking memory barrier with large performance penalty.

I believe you're discussing 'Arc'. 'Rc' is not thread safe.

then this is not "closest to GC languages", since GC langs usually provide memory management with respect to concurrency.

It's probably slower, but unlike normal GCed languages, it's not actually anywhere close to everything.

Many garbage collectors (e.g. CPython’s) will use reference counting as part of the process. If a reference count hits zero, the object can be destructed, prolonging the time between mark-and-sweep passes.

The performance difference, though, is mainly in switching over to a compiled language in the first place.