Operating systems 5) Why is a mode switch between threads cheaper than a mode switch between...

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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