Daniel Arbuckle's Mastering Python

Multithreading is not good for servers

There are ways to write a server that would use only a single stream of execution, but if we have a way of writing servers that would probably introduce fewer bugs, why not? The problem is resource overhead.

Every process running on a computer uses up memory and CPU time, of course; however, in addition to the memory and CPU time, the process needs to run its code as well. The operating system also needs to expend some resources to manage the process. As it happens, the time spent on switching between processes is significant.

Memory overhead is enough; it becomes a limiting factor for how many clients a multiprocess server can handle simultaneously; other internal operating system resources may be even ...