Good questions.

> To replicate erlang, is easier if used the Actor model? Or can be done with CSP?

There is overlap between then two. CSP is _usually_ synchronous and Actor model is asyncronous. CSP is focused on channels. As in you send messages to a channel and the other side receives them. Channel has an identity. In Erlang you send a message to a process (its main concurrency context). A process has a process ID used to identify it. Like say you have an address at your house and and I send a letter to you.

Goroutines don't have identity. You can't easily send a message to a goroutine. Kill a goroutine, see if it died to start another one and so on.

> Also, what is need to made a soft realtime language/runtime?

Quite simply you need one part of the system to not block other parts from making progress (returning a result). Imagine your serve a page to one user but because some other user is sent some input that take a long time to process, the first user doesn't get a response, he has to wait.

Or say you have some data structures and a common heap between concurrency contexts. A garbage collector might have to stop all goroutines in order to check if it can collect any garbage. So that introduces a pause. Java Azul JVM the only VM with shared that that has concurrent and pauseles garbage collector. It is very impressive, look it up how it works. In Erlang it is easy. Processes heaps are private to each process so they can be collected independently without getting in the way.

> Java Azul JVM

Oh I agree 100% here, I had a Java version of a project that went from 15k qps to 60k qps just by switching to the Azul JVM.

That said I still ended up crushing that with Nginx/LuaJIT and I didn't need a proprietary JVM that wouldn't work on some systems because of kernel modules it needed to install etc.

"Channel has an identity". In wikipedia (https://en.wikipedia.org/wiki/Communicating_sequential_proce...) say "CSP processes are anonymous", but don't tell about the channels. So, how can a channel have a identity? Why is usefull? If the channel is a type declaration, why I need something else? This is something that actor have (PID, because you send "emails") that I don't see why is necesary in CSP

> In Erlang it is easy. Processes heaps are private to each process so they can be collected independently without getting in the way.

But that comes at the expense of throughput, and it doesn't help with shared state (ETS)