Threads Vs Processes Generally

1) Why is thread creation less expensive than process creation?

2) What is the difference between a thread and a subprocess? How would this relate to the above quest开发者_开发问答ion?

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When a process is created it is allocated heap and stack memory. Threads on the other hand only get a stack and share the heap with the parent process. This means that even if you just consider memory allocation it is more "expensive" to create a process than a thread.

Subprocesses are simply processes that were created by another process. They are otherwise independent and get their own memory space. Here's an article that goes into some more detail.

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The answer to this question is probably very OS dependent but a general rule :

1. Threads of a process live in the same virtual memory space as their parent. So a thread creation is less expensive than a process creation because the underlying operating system doesn't need to create a full virtual memory space.

2. A subprocess is just another process spawned by a parent.