[adrusi]

I don't know if live reload is widely used or not, but the other features of erlang allow you to create systems that see decades of uptime. But without code hot swapping your uptime is limited by how often you ship new code. Typically a distributed application will be made of independent programs on various machines that you can upgrade and spawn and kill at your leisure. In erlang your entire distributed application is kind of like just one program, and what was an executable in the traditional model is now a module, so in order to match the capabilities of a traditional system, you need to be able to upgrade modules without killing everything.

---

There are a number of other dynamically typed languages that have fast implementations. Javascript has a few; Common Lisp, Self, Julia, to name some others. They'll never be as fast as C, certainly not when comparing highly optimized programs, but they're fast. It looks like most dynamically typed languages can be made to run 10x slower than C. Compare that to CPython and HiPE which are more like 100x slower.

I don't think code reloading would hurt JIT performance too much. The prerequisites for runtime specialization of procedures basically accomodate eveything hot swapping would need. I also think the way people use Erlang's type system is probably more ammenable to conservative type inference than the existing fast dynamic languages, and that's one of the more important metrics.