FIFO scheduling results in the shortest possible average response time if the jobs happen to arrive in the ready queue with the shortest completion times first (or, as a special case, if all jobs have the same completion time).
Round robin scheduling behaves identically to FIFO if the job lengths are no longer than the length of the time slice.
Round robin scheduling behaves identically to FIFO if the job lengths are no longer than the length of the time slice. Round robin scheduling performs poorly compared to FIFO if the job lengths are all the same, and much greater than the time slice length. $\text{S2}$ is false. The dispatcher is only responsible for switching threads; the scheduler determines the thread priorities, based on the system’s scheduling algorithms.
$\text{The Dispatcher:}$
Once the CPU scheduler selects a process for execution, it is the job of the dispatcher to start the selected process. Starting this process involves three steps:
- Switching context
- Switching to user mode
- Jumping to the proper location in the program to start or resume execution
The latency introduced by the dispatch is called the dispatch latency. Obviously, this should be as small as possible -- but is most critical in real-time system, those systems that must meet deadlines associated with real world events.
