Operating Systems Question Bank with Answers 01

List the advantages of user level threads in operating systems

Question:

List the advantages of user-level threads.

Answer:

Following are the advantages of user level threads;

• The most obvious advantage of this technique is that a user-level threads package can be implemented on an Operating System that does not support threads. Some implementations of Java have user-level threads because the underlying OS doesn’t.

• User-level threads do not require modification to operating systems.

• Simple Representation: Each thread is represented simply by a PC, registers, stack and a small control block, all stored in the user process address space.

• Simple Management:  This simply means that creating a thread, switching between threads and synchronization between threads can all be done without intervention of the kernel (No switch into kernel mode and this saves time). No system call is required to create. Just a normal library procedure call can do.

• Control can be application specific. Sometimes the OS doesn’t give the type of control an application needs. e.g. precise priority levels, changing scheduling decisions according to state changes

• Fast and Efficient:  Thread switching is not much more expensive than a procedure call.

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