1. reason – the control blocks for processes are larger

than for threads (hold more state information), so the

amount of information to move during the thread switching

is less than for process context switching

2. reason – the major reason is that the memory management

is much simpler for threads than for processes. Threads

share their memory so during mode switching, memory

information does not have to be exchanged/changed, pages

and page tables do not have to be switched, etc. This makes

the thread context switch much cheaper than for processes.

In case of processes the memory pieces (pages) need to be

exchanged, etc. (Will talk about the details in few weeks).

3. reason – threads do not have to worry about accounting,

etc, so do not have to fill out all the information about

accounting and other process specific information in their

thread control block, so keeping the thread control block

consistent is much faster

4. reason – threads share files, so when mode switch

happens in threads, these information stay the same and

threads do not have to worry about it (similar to

accounting information) and that makes the mode switch much

faster.