Process Concepts and Cpu Scheduling · Operating Systems · GATE CSE

Processes $P 1, P 2, P 3, P 4$ arrive in that order at times $0,1,2$, and 8 milliseconds respectively, and have execution times of $10,13,6$, and 9 milliseconds respectively. Shortest Remaining Time First (SRTF) algorithm is used as the CPU scheduling policy. Ignore context switching times.
Which ONE of the following correctly gives the average turnaround time of the four processes in milliseconds?

Suppose in a multiprogramming environment, the following C program segment is executed. A process goes into I/O queue whenever an I/O related operation is performed. Assume that there will always be a context switch whenever a process requests for an I/O, and also whenever the process returns from an I/O. The number of times the process will enter the ready queue during its lifetime (not counting the time the process enters the ready queue when it is run initially) is _________ . (Answer in integer)

int main( )
{
    int x = 0,i=0;
    scanf("%d", &x);
    for(i=0; i<20;i++)
    {
        x=x+20;
        printf("%d\n", x);
    }
    return 0;
}

Consider a process P running on a CPU. Which one or more of the following events will always trigger a context switch by the OS that results in process P moving to a non-running state (e.g., ready, blocked)?

Which of the following process state transitions is/are NOT possible?

Which one or more of the following need to be saved on a context switch from one thread (T1) of a process to another thread (T2) of the same process?

Which one or more of the following CPU scheduling algorithms can potentially cause starvation?

         #include < unistd.h >
            int main ()
            {
                  int i ;
                  for (i=0; i<10; i++)
                         if (i%2 == 0) fork ( ) ;
                  return 0 ;
            }

$$ * \,\,\,$$ Interrupt from $$CPU$$ temperature sensor (raises interrupt if $$CPU$$ temperature is too high)

$$ * \,\,\,$$ Interrupt from Mouse (raises interrupt if the mouse is moved or a button is pressed)

$$ * \,\,\,$$ Interrupt from keyboard (raises interrupt when a key is pressed or release)

$$ * \,\,\,$$ Interrupt from Hard Disk (raises interrupt when a disk read is completed)>/p>

Which one these will be handled at the HIGHEST priority?

Which of the following is TRUE?

Group-1
(P) Gang Scheduling
(Q) Rate Monotonic Scheduling
(R) Fair Share Scheduling

Group-2
(1) Guaranteed Scheduling
(2) Real-time Scheduling
(3) Thread Scheduling

Which one of the following statements is FALSE?

Which of the above statements are true?

A computer has two processors, $M_1$ and $M_2$. Four processes $P_1, P_2, P_3, P_4$ with CPU bursts of $20,16,25$, and 10 milliseconds, respectively, arrive at the same time and these are the only processes in the system. The scheduler uses non-preemptive priority scheduling, with priorities decided as follows:

$\bullet$ $M_1$ uses priority of execution for the processes as, $P_1>P_3>P_2>P_4$, i.e., $P_1$ and $P_4$ have highest and lowest priorities, respectively.

$\bullet$ $M_2$ uses priority of execution for the processes as, $P_2>P_3>P_4>P_1$, i.e., $P_2$ and $P_1$ have highest and lowest priorities, respectively.

A process $P_i$ is scheduled to a processor $M_k$, if the processor is free and no other process $P_j$ is waiting with higher priority. At any given point of time, a process can be allocated to any one of the free processors without violating the execution priority rules. Ignore the context switch time. What will be the average waiting time of the processes in milliseconds?

Consider a single processor system with four processes A, B, C, and D, represented as given below, where for each process the first value is its arrival time, and the second value is its CPU burst time.

A (0, 10), B (2, 6), C (4, 3), and D (6, 7).

Which one of the following options gives the average waiting times when preemptive Shortest Remaining Time First (SRTF) and Non-Preemptive Shortest Job First (NP-SJF) CPU scheduling algorithms are applied to the processes?

Consider four processes P, Q, R and S scheduled on a CPU as per round robin algorithm with a time quantum of 4 units. The processes arrive in the order P, Q, R, S, all at time t = 0. There is exactly one context switch from S to Q, exactly one context switch from R to Q, and exactly two context switches from Q to R. There is no context switch from S to P. Switching to a ready process after the termination of another process is also considered a context switch. Which one of the following is NOT possible as CPU burst time (in time units) of these processes?

The average turn around time of these processes is milliseconds.

The average waiting time (in milliseconds) of the processes is ________.

The processes $$A, B,$$ and $$C$$ are started at times $$0, 5$$ and $$10$$ milliseconds respectively, in a pure time sharing system (round robin scheduling) that uses a time slice of $$50$$ milliseconds. The time in milliseconds at which process $$C$$ would complete its first $${\rm I}/O$$ operation is __________.

Using the $$shortest$$ $$remaining$$ $$time$$ $$first$$ scheduling algorithm, the average process turnaround time (in $$msec$$) is _______.

The completion order of the $$3$$ processes under the policies $$FCFS$$ and $$RR2$$ (round robin scheduling with $$CPU$$ quantum of $$2$$ time units) are

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

Now consider the following statements:
$$1.\,\,\,$$ If a process makes a transition $$D,$$ it would result in another process making transition $$A$$ immediately.
$$2.\,\,\,$$ $$A$$ process $${P_2}$$ in blocked state can make transition $$E$$ while another process $${P_1}$$ is in running state.
$$3.\,\,\,$$ The $$OS$$ uses preemptive scheduling.
$$4.\,\,\,$$ The $$OS$$ uses non-preemptive scheduling. Which of the above statements are TRUE?

for (i = 0; i < n; i + +) fork ( ); 

What is the total waiting time for process $$P2?$$

if (fork() == 0)
{
   a = a + 5;
   printf("%d, %d \n", a, &a);
}
else
{
   a = a - 5;
   printf ("%d, %d \n", a, &a);
}

What is the average turnaround time for these processes with the preemptive shortest remaining processing time first $$(SRTF)$$ algorithm?

The jobs are assumed to have arrived at time $${0^ + }$$ and in the order $$p,q,r,s,t.$$ Calculate the departure time (completion time) for job $$p$$ if scheduling is round robin with time slice$$1.$$