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Consider a virtual page reference string 1, 2, 3, 2, 4, 2, 5, 2, 3, 4. Suppose LRU page replacement algorithm is implemented with 3 page frames in main memory. Then the number of page faults are ______

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UGC NET Computer Science (Paper 2) July 2018 Paper
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  1. 5
  2. 7
  3. 9
  4. 10

Answer (Detailed Solution Below)

Option 2 : 7
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Detailed Solution

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Concept:

LRU (Least recently used) page replacement algorithm is based on the assumption that the page that has been used in the last few instructions will be referenced in the next few instructions. It replaces the page that has not been referenced for the longest time.

Explanation:

Reference string: 1, 2, 3, 2, 4, 2, 5, 2, 3, 4

Number of frames = 3

 

1

2

2

2

2

 

2

3

4

5

3

 

3

4

5

3

4

Page fault

3

1

1

1

1

 

Here, total page faults = 3 + 1 + 1 + 1 + 1 = 7

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More Page Replacement Policy Questions

Q1.Given as 4 GB (= 4.3 × 109 bytes) of virtual space and typical page size of 4 KB and each page table entry is 5 bytes. How many virtual pages would this imply ? What is the size of whole page table ? 
Q2.Consider the following statements: S1: LRU page replacement algorithm suffers from the belady's anomaly S2: Shortest remaining time first scheduling may cause starvations S3: Stack is shared by all threads in a process 
Q3.Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R. A virtual memory system uses first-in first-out page replacement policy and allocates a fixed number of frames to a process Assertion A: Increasing number of page frames allocated to a process sometimes increases the page fault rate. Reason R: Some programs do not exhibit locality of reference. In the light of the above statements, choose the correct answer from the options given below. 
Q4.Consider the following reference string of pages made by a processor : 4, 7, 5, 7, 6, 7, 10, 4, 8, 5, 8, 6, 8, 11, 4, 9, 5, 9, 6, 9, 12, 4, 7, 5, 7 Assume that the number of page frames allocated in the main memory is four. What is the number of page faults generated using Least Recently Used (LRU) replacement technique?
Q5.For the following page reference string 4, 3, 2, 1, 4, 3, 5, 4, 3, 2, 1, 5. the number of page faults that occur in Least Recently Used (LRU) page replacement algorithm with frame size 3 is
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Q9.A process refers to 5 pages, A, B, C, D, E in the order: A, B, C, D, A, B, E, A, B, C, D, E. If the page replacement algorithm is FIFO, the number of page transfers with an empty internal store of 3 frames is 7. If the number of page frames is increased to 4, then the number of page transfers :

More Virtual Memory Questions

Q1.Given as 4 GB (= 4.3 × 109 bytes) of virtual space and typical page size of 4 KB and each page table entry is 5 bytes. How many virtual pages would this imply ? What is the size of whole page table ? 
Q2.Consider the following statements: S1: LRU page replacement algorithm suffers from the belady's anomaly S2: Shortest remaining time first scheduling may cause starvations S3: Stack is shared by all threads in a process 
Q3.Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R. A virtual memory system uses first-in first-out page replacement policy and allocates a fixed number of frames to a process Assertion A: Increasing number of page frames allocated to a process sometimes increases the page fault rate. Reason R: Some programs do not exhibit locality of reference. In the light of the above statements, choose the correct answer from the options given below. 
Q4.Consider the following reference string of pages made by a processor : 4, 7, 5, 7, 6, 7, 10, 4, 8, 5, 8, 6, 8, 11, 4, 9, 5, 9, 6, 9, 12, 4, 7, 5, 7 Assume that the number of page frames allocated in the main memory is four. What is the number of page faults generated using Least Recently Used (LRU) replacement technique?
Q5.For the following page reference string 4, 3, 2, 1, 4, 3, 5, 4, 3, 2, 1, 5. the number of page faults that occur in Least Recently Used (LRU) page replacement algorithm with frame size 3 is
Q6.When a page fault occurs before an executing instruction is complete :
Q7.The aim of creating page replacement algorithms is to :
Q8.A FIFO replacement algorithm associates with each page the ______.
Q9.A process refers to 5 pages, A, B, C, D, E in the order: A, B, C, D, A, B, E, A, B, C, D, E. If the page replacement algorithm is FIFO, the number of page transfers with an empty internal store of 3 frames is 7. If the number of page frames is increased to 4, then the number of page transfers :
Q10.Thrashing

More Operating Systems Questions

Q1._________ command is used to duplicate the entire disk in DOS.
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Q5.Command interpreter is also known as ______. 
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Q10.Match List-I with List-II List I List II A. LRU I. A page is written to secondary memory only when it has been selected for replacement B. Demand cleaning II. A page that has not been referenced for the longest time is replaced C. Long term scheduling III. The decision to add to the number of processes that are partially or fully in main memory D. Medium term scheduling  IV. The decision to add to the pool of processes to be executed Choose the correct answer from the options given below :
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