Mode switch among threads

Question

Tell reasons why a Mode switch among threads may be cheaper than a Mode switch among processes?

Answer 1

1. Reason – the control blocks for processes are bigger than for threads (store more state information), therefore the amount of information to move throughout the thread switching is less than for process context switching

2. Reason – the main reason is that the memory management is simpler for threads than for processes. Threads share their memory so throughout mode switching, memory information ought not to be exchanged/changed, pages & page tables do not have to be switched, etc. It makes the thread context switch much cheaper than for processes. In particular case of processes the memory pieces (pages) require to be exchanged, etc.