Comment by pocksuppet
9 hours ago
Languages have affordances. At the extreme ends are PHP, and Java or Go. PHP runs a separate logical process on every request which can't share resources with any other request. Almost everyone using Go is writing a long-running server process because that's how the libraries are designed. Almost everyone using Java is writing a long-running process or a module for one, because Java startup times are obscene. Java also has a very convenient synchronization primitive.
Multi-threaded processes are used because that's the most efficient model, hardware wise. Tasks can maximally share resources. It's not to do with library design or startup time.
The hardware doesn't know anything about processes. The most efficient model, hardware-wise, is to disable virtual memory and never do a context switch, but we don't see anyone programming like that, except for the crazy SDN folks who are doing software packet forwarding at hundred-gigabit rates.