2. Consider the following set of processes, each with its arrival time, burst time, and priority: Arrival Time Burst Time Priority 0 6 IIII 1 4 2 8 3 Process P1 P2 P3 P4 2 3 1 2 4 Apply the Multilevel Queue scheduling algorithm with two queues, one for high-priority processes (P1 and P2) and one for low-priority processes (P3 and P4), and a time quantum of for the high-priority queue and 5 for the low-priority queue. Calculate the average waiting time and turnaround time for each queue, as well as the overall average waiting time and turnaroun time.

2. Consider the following set of processes, each with its arrival time, burst time, and priority: Arrival Time Burst Time Priority 0 6 IIII 1 4 2 8 3 Process P1 P2 P3 P4 2 3 1 2 4 Apply the Multilevel Queue scheduling algorithm with two queues, one for high-priority processes (P1 and P2) and one for low-priority processes (P3 and P4), and a time quantum of for the high-priority queue and 5 for the low-priority queue. Calculate the average waiting time and turnaround time for each queue, as well as the overall average waiting time and turnaroun time.

Database System Concepts

7th Edition

ISBN:9780078022159

Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Chapter1: Introduction

Section: Chapter Questions

Problem 1PE

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Subject: Operating Systems
In Round Robin scheduling, when three processes have to enter the ready-queue at the same instant, if one process (A) has just finished 1/o, the other (B) has been pre-empted from CPU due to expiration of its time quantum and the third (C) has just started, which one will be inserted last (i.e. with lowest priority)? O The process that has just finished I/O. O One of the three will be randomly selected. O The process that has been pre-empted from CPU due to expiration of its time quantum. O The process that has just started.
2 Recall the various deadlock detection and prevention algorithms we've discussed in class and consider the following snapshot of a system with five processes (P10, P11, P12, P13, P14) and four resources (R1, R2, R3, R4). R1, R2, R3, and R4 have a total of 11, 13, 7, and 9 resources, respectively. There are no current outstanding queued unsatisfied requests. Table 1: Allocation Table 2: Max R3 R4 PID R.1 R2 R3 R4 PID R1 10 4 11 3 12 1 215 2 1 3 10 13 0 5 0 14 1 3012 4 11 12 012 1 13 1 14 231323 75524 R2 5 5 432300 36373 8 Is the system currently in a safe or unsafe state? If safe, provide the process execution order. If unsafe explain your answer.
8. Consider one disk with 400 cylinders, numbered 0 to 399. Assume the current position of head is at cylinder 130. The request queue is given as follows: 150, 40, 350, 100, 280 For each of the disk-scheduling algorithms given below, show (by plotting in the graphs below) the current position of head based on the disk arm movement to satisfy the above requests, and count the total distance (in cylinders) of the disk arm movement. a. First Come First Served (FCFS) 0 40 100 1.30 150 Total distance (disk am movement) = b. Shortest Seek Time First (SSTF) 40 100 130 150 0 Total distance (disk arm movement) = c. LOOK - in the direction of increasing track number 0 40 100 130 150 Total distance (disk arm movement) = 280 280 280 350 350 350 399 399 399
If you are working with scheduling policies, you are requested to investigate the variation of round robin in which a process that has used its full time quantum is returned to the end of the READY queue, while one that has used half of its time quantum is returned to the middle of the queue and one that has used one-fourth of its time quantum goes to a place one-fourth of the distance away from the beginning of the queue. 5.1 Explain the advantages and disadvantages of this scheduling policy. 5.2 Identify the user group that would find this most advantageous. 5.3 Describe the unique threats to a data centre posed by disgruntled employees. Describe how you would identify such people, if possible, and how you would protect your system from these threats. 5.4 What are the parameters that affect the efficiency of the round robin?
Suppose that the following processes arrive for execution at the times indicated. Each process has the shown priorities and will run for the amount of time listed (all times are in ms) Process Arrival Time Burst Time Priority Queue P1 15 3 P2 20 3 P3 20 20 P4 25 10 2 P5 30 5 2 P6 35 15 1 To schedule the execution of these process, a preemptive multi-level queue scheduler is designed to apply the following policy at each decision instant (namely whenever a new process arrives and whenever a burst completes execution): • Serve the process at the highest priority queue first • If two processes are in the same queue: . If they have different remaining time, follow the SRTF policy o If they have same remining time, follow a RR policy (slice time = 2 ms) Given the above: 1. Show the scheduling order of the bursts using a Gantt chart.
correct answer is 13. Can you explain by sperately please?
Question 1 Two processes need to acquire 3 mutexes in order to access a particular shared queue. The mutexes are numerically ordered. Process 1 acquires the mutexes in 1, 2, 3 order and Process 2 acquires them in 3, 2, 1 order. If a process tries to acquire a mutex held by the other process, a conflict is detected, both processes release their mutexes, wait for some (random) time, and try again. Does the proposed scheme guarantee the processes can always successfully access the shared queue? Yes, but at the cost of efficiency Yes, no livelock is possible because the mutexes are numerically ordered No, starvation is possible No, priority inversion is possible
Concurrent Processes / Monitors select which is true options: a CV (condition variable) queues in a monitor store suspended processes waiting on the corresponding condition. b The "Signal and Wait" approach (Hoare semantics) leads to more efficient implementation and reduces the number of context switches. c Two or more processes can be active in the same monitor simultaneously. d When the "Signal and Continue"-approach (Mesa semantics) is applied, the signaling process P continues executing. e The monitor-based solution to the Dining-Philosophers problem discussed in class is restricted to 5 philosophers.