OPERATING SYSTEMS 2

Which of the following scheduling algorithms is non-preemptive? (GATE CS 2002) 

• Round Robin 
  

• First-In First-Out 
  

• Multilevel Queue Scheduling 
  

• Multilevel Queue Scheduling with Feedback 

consider the 3 processes, P1, P2 and P3 shown in the table

The completion order of the 3 processes under the policies FCFS and RRS (round robin scheduling with CPU quantum of 2 time units) are

• FCFS: P1, P2, P3 RR2: P1, P2, P3

• FCFS: P1, P3, P2 RR2: P1, P3, P2

• FCFS: P1, P2, P3 RR2: P1, P3, P2

• FCFS: P1, P3, P2 RR2: P1, P2, P3

Consider the following table of arrival time and burst time for three processes P0, P1 and P2.

The pre-emptive shortest job first scheduling algorithm is used. Scheduling is carried out only at arrival or completion of processes. What is the average waiting time for the three processes?

• 5.0 ms

• 4.33 ms

• 6.33 ms

• 7.33 ms

Which of the following statements are true? (GATE CS 2010)
I. Shortest remaining time first scheduling may cause starvation
II. Preemptive scheduling may cause starvation
III. Round robin is better than FCFS in terms of response time

• I only

• I and III only

• II and III only

• I, II and III

1) In the following process state transition diagram for a uniprocessor system, assume that there are always some processes in the ready state: Now consider the following statements:

I. If a process makes a transition D, it would result in another process making transition A immediately.
II. A process P2 in blocked state can make transition E while another process P1 is in running state.
III. The OS uses preemptive scheduling.
IV. The OS uses non-preemptive scheduling.

Which of the above statements are TRUE?

• I and II

• I and III

• II and III

• II and IV

An operating system uses Shortest Remaining Time first (SRT) process scheduling algorithm. Consider the arrival times and execution times for the following processes: 

What is the total waiting time for process P2?

• 5

• 15

• 40

• 55

Consider three CPU-intensive processes, which require 10, 20 and 30 time units and arrive at times 0, 2 and 6, respectively. How many context switches are needed if the operating system implements a shortest remaining time first scheduling algorithm? Do not count the context switches at time zero and at the end.

• 1

• 2

• 3

• 4

Consider three processes, all arriving at time zero, with total execution time of 10, 20 and 30 units, respectively. Each process spends the first 20% of execution time doing I/O, the next 70% of time doing computation, and the last 10% of time doing I/O again. The operating system uses a shortest remaining compute time first scheduling algorithm and schedules a new process either when the running process gets blocked on I/O or when the running process finishes its compute burst. Assume that all I/O operations can be overlapped as much as possible. For what percentage of time does the CPU remain idle?

• 0%

• 10.6%

• 30.0%

• 89.4%

Consider the following statements about process state transitions for a system using preemptive scheduling.
I. A running process can move to ready state.
II. A ready process can move to ready state.
III. A blocked process can move to running state.
IV. A blocked process can move to ready state.

• I, II AND III ONLY

• II AND III ONLY

• I, II AND IV ONLY

• I, II, III AND IV ONLY

The following C program is executed on a Unix/Linux system:
The total number of child processes created is _____.

We know, n - fork statements will create 2ⁿ - 1 childs.

• 25

• 31

• 33

• 42