Operating Systems 173323 (3 cu)

Exercise 5

Group 1: November 12, at 16-18 pm (T/B181)
Group 2: November 12, at 10-12 am (T/B180)

CPU scheduling

  1. Consider the following set of processes, with the arrival times and the length of the CPU-burst times given in milliseconds, and the priorities given so that smaller priority number means a higher priority. 

         Process    Arrival time   Burst time     Priority
     -------    ------------   ----------     --------
        P1           0             10            3
        P2           2              1            1
        P3           3              2            3
        P4           4              1            4
        P5           6              5            2

    Draw a Gantt chart illustrating the execution of these processes using a preemptive priority scheduling. (Use FCFS for equal priority processes)

    Calculate a waiting time and a turnaround time for each process, and an average waiting time and an average turnaround time for the scheduling.

  2. Consider the following set of processes, with the length of the CPU-burst time given in milliseconds. 

         Process    Burst time
     -------    ----------
        P1          10
        P2           1
        P3           2
        P4           1
        P5           5

    The processes are assumed to have arrived in the order P1,P2,P3,P4,P5, all at time 0.

    Draw a Gantt chart illustrating the execution of these processes using RR (time quantum = 1 ms) scheduling.

    Calculate a waiting time and a turnaround time for each process, and an average waiting time and an average turnaround time for the scheduling.

  3. Consider the following set of processes, with the arrival times and the length of the CPU-burst times given in milliseconds. 

         Process    Arrival time   Burst time
     -------    ------------   ----------
        P1          0              10
        P2          2               1
        P3          3               2
        P4          4               1
        P5          6               5
    Draw a Gantt chart illustrating the execution of these processes using RR (time quantum = 3 ms) scheduling.

    Calculate a waiting time and a turnaround time for each process, and an average waiting time and an average turnaround time for a scheduling.

  4. Consider the following set of processes, with the arrival times and the length of the CPU-burst times given in milliseconds. 
         Process    Arrival time   Burst time
     -------    ------------   ----------
        P1          0              17
        P2         12              25
        P3         28               8
        P4         36              32
        P5         46              18

    Draw a Gantt chart illustrating the execution of these processes using a Multilevel Feedback Queue Scheduling. Use the same structure of the model as in the lectures: (queue 0: time quantum 8), (queue 1: time quantum 16), (queue 2: FCFS). Queues 0 and 1 are served as FCFS with time quantums 8 and 16, respectively.

  5. Consider the Multilevel Feedback Queue Scheduling in the previous task (task number 4).