Question

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 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

Answer 1

Both statements P and Q are true. P refers to Belady's anomaly, which appears in some paging algorithms like FIFO, and Q appropriately notes that not all programs have locality of reference. However, Q is not the cause of P.

Step-by-step explanation:

The question pertains to the behavior of a virtual memory system that is using a First In First Out (FIFO) page replacement policy. Regarding the statements given:

• P: This is known as Belady's anomaly, where under certain circumstances, increasing the number of page frames can lead to an increase in the page fault rate. This is counterintuitive but true for certain page replacement algorithms like FIFO.
• Q: This statement is true as well. Locality of reference implies that a program will tend to access a relatively small set of pages repeatedly over a short period of time. However, not all programs exhibit this behavior. Some might access a wide range of different pages sporadically, leading to poor cache efficiency and an increased page fault rate.

Therefore, the correct answer would be: Both P and Q are true, but Q is not the reason for P.

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