Why are threads called lightweight processes?

Question

A thread is \"lightweight\" because most of the overhead has already been accomplished through the creation of its process.

I found this in one of the tutorials.

Answer 1

Process creation is "expensive", because it has to set up a complete new virtual memory space for the process with it's own address space. "expensive" means takes a lot of CPU time.

Threads don't need to do this, just change a few pointers around, so it's much "cheaper" than creating a process. The reason threads don't need this is because they run in the address space, and virtual memory of the parent process.

Every process must have at least one thread. So if you think about it, creating a process means creating the process AND creating a thread. Obviously, creating only a thread will take less time and work by the computer.

In addition, threads are "lightweight" because threads can interact without the need of inter-process communication. Switching between threads is "cheaper" than switching between processes (again, just moving some pointers around). And inter-process communication requires more expensive communication than threads.