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OS : 2007 GATE Questions

Questions : 5

QID : 282GATE-2007, 1M

Group 1 contains some CPU scheduling algorithms and Group 2 contains some applications. Match entries in Group 1 to entries in Group 2.

Group I                                       Group II
(P) Gang Scheduling                    (1) Guaranteed Scheduling
(Q) Rate Monotonic Scheduling     (2) Real-time Scheduling
(R) Fair Share Scheduling             (3) Thread Scheduling

A) P - 3 Q - 2 R - 1
B) P - 1 Q - 2 R - 3
C) P - 2 Q - 3 R - 1
D) P - 1 Q - 3 R - 2
Ans : Option A
Solution :
QID : 283GATE-2007, 1M

Consider the following statements about user level threads and kernel level threads. Which one of the following statements is FALSE?

A) Context switch time is longer for kernel level threads than for user level threads.
B) User level threads do not need any hardware support.
C) Related kernel level threads can be scheduled on different processors in a multi-processor system.
D) Blocking one kernel level thread blocks all related threads.
Ans : Option D
Solution :
Kernel level threads are independent of each other. Its the user level threads where if one thread gets blocked the others are also blocked for the same process in case of one to one or many to one model.
QID : 284GATE-2007, 2M

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

Process   Execution time   Arrival time
P1            20                    0
P2            25                   15
P3            10                   30
P4            15                   45

What is the total waiting time for process P2?

A) 5
B) 15
C) 40
D) 55
Ans : Option B
Solution :
QID : 286GATE-2007, 2M

A single processor system has three resource types X, Y and Z, which are shared by three processes. There are 5 units of each resource type. Consider the following scenario, where the column alloc denotes the number of units of each resource type allocated to each process, and the column request denotes the number of units of each resource type requested by a process in order to complete execution. Which of these processes will finish LAST?

         alloc      request
       X  Y  Z     X  Y   Z
P0   1  2  1     1   0   3
P1   2  0  1     0   1   2
P2   2  2  1     1   2   0

A) P0
B) P1
C) P2
D) None of the above, since the system is in a deadlock
Ans : Option C
Solution :
Available resources are (0, 1, 2) respectively.

P1 can take these resources and execute.
After P1 finishes, availability will be (2, 1, 3)

Now P0 's request can be satisfied, so it will execute and finish
and finally the P2's request can be satisfied.

So safe sequence is P1, P0, P2
QID : 285GATE-2007, 2M

A virtual memory system uses First In First Out (FIFO) page replacement policy and allocates a fixed number of frames to a process. Consider the following statements:

P: Increasing the number of page frames allocated to a process sometimes increases the page fault rate.
Q: Some programs do not exhibit locality of reference.

Which one of the following is TRUE?

A) Both P and Q are true, and Q is the reason for P
B) Both P and Q are true, but Q is not the reason for P
C) P is false, but Q is true
D) Both P and Q are false
Ans : Option B
Solution :

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