In order to determine which statements regarding CPU scheduling are correct, we need to examine each statement individually in the context of operating systems and CPU scheduling concepts.
Turnaround time includes waiting time. Turnaround time is the total time taken for a particular process from submission to completion. It is calculated as the sum of the actual executing time, the waiting time in the ready queue, and any additional delays. Mathematically, Turnaround\ Time = Completion\ Time - Arrival\ Time. This clearly includes the waiting time, so this statement is correct.
The goal is to only maximize CPU utilization and minimize throughput.
This statement is partially incorrect. The goals of CPU scheduling include maximizing CPU utilization, minimizing waiting time, turnaround time, response time, and maximizing throughput. Throughput should be maximized, and not minimized as stated. Therefore, this statement is incorrect.
Round-robin policy can be used even when the CPU time required by each of the processes is not known a priori.
The Round-robin scheduling algorithm is designed to equally distribute CPU time among processes in a cyclic manner. It is essentially time-sharing and does not require prior knowledge of the CPU burst times of processes. This makes the statement correct.
Implementing preemptive scheduling needs hardware support.
Preemptive scheduling allows a process to be interrupted and moved to the ready queue without its completion. This requires support from hardware timers and the ability to handle such interrupts to manage the switching between processes. Thus, this statement is correct.
Conclusively, the statements that are correct are:
Turnaround time includes waiting time.
Round-robin policy can be used even when the CPU time required by each of the processes is not known a priori.