Question

operating systems

5) Why is a mode switch between threads cheaper than a mode switch between processes? (0.5 points) 6) List 2 advantages and 2 disadvantages of ULT's vs KLTS. (0.5 points) 7) List 4 thread operations associated with a change is thread state (0.5 points) 8) List 3 categories of Process Control Block Elements (0.5 points) 9) What is the difference between traditional and modern UNIX thread support? (0.5 points)

Answer 1

5)

This is because the mapped memory will be the same as threads share the same memory space whereas processes memory spaces are protected from each other.

6)

User level threads:

Advantages:

• User-level threads does not require modification to operating systems.
• Each thread is represented simply by a PC, registers, stack and a small control block, all stored in the user process address space.

Disadvantages:

• There is a lack of coordination between threads and operating system kernel.
• User-level threads requires non-blocking systems call i.e., a multithreaded kernel.

Kernel Level threads:

Advantages:

• Because kernel has full knowledge of all threads, Scheduler may decide to give more time to a process having large number of threads than process having small number of threads.
• Kernel-level threads are especially good for applications that frequently block.

Disadvantages:

• The kernel-level threads are slow and inefficient.
• It require a full thread control block (TCB) for each thread to maintain information about threads. As a result there is significant overhead and increased in kernel complexity.

7)

• Spawn
• Block
• Unblock
• Finish

8)

• Naming the process
• State of the process
• Resources allocated to the process

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