Concurrency and Multithreading

Question

I\'m not very experienced with subjects such as Concurrency and Multithreading. In fact, in most of my web-development career I had never needed to touch these subjects.

Answer 1

Regarding your question of why fork() instead of threading: when you use separate processes, you get automatic separation of address spaces. In multithreaded programs, it is very common for threads to communicate using their (naturally) shared memory. This is very efficient, but it is also hard to get all the synchronization between threads right, and this is why some languages are better at multithreading than others: they provide better abstractions to handle the common cases of communication between threads.

With separate processes, you don't have these problems to the same extent. Typically, you set up communication between processes to follow some form of message-passing pattern, which is easier to get right. (Well, you can use shared memory between processes too, but that's not as common as message passing.) On Unix systems fork() has typically been very cheap, so traditional design of concurrent programs in Unix uses processes, and pipes to communicate between them, but on systems where process creation is an expensive operation, threads are often regarded as the better approach.