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Questions and Answers
What replacement strategy was indicated as optimal in the final table?
What replacement strategy was indicated as optimal in the final table?
- First In First Out
- Least Recently Used
- Optimal (correct)
- Random Replacement
In the given context, which page has the highest frequency of access in the stream?
In the given context, which page has the highest frequency of access in the stream?
- d
- b
- c
- a (correct)
Which frame is least accessed in the page stream when using the Least Recently Used (LRU) strategy?
Which frame is least accessed in the page stream when using the Least Recently Used (LRU) strategy?
- c
- f (correct)
- e
- a
How many times does the page 'c' result in a fault in the optimal strategy?
How many times does the page 'c' result in a fault in the optimal strategy?
What is the first page to cause a fault in the provided page stream?
What is the first page to cause a fault in the provided page stream?
In the Clock replacement algorithm, how is a frame identified as a candidate for replacement?
In the Clock replacement algorithm, how is a frame identified as a candidate for replacement?
What is the main purpose of cleaning policies in memory management?
What is the main purpose of cleaning policies in memory management?
What distinguishes demand cleaning from pre-cleaning in memory management?
What distinguishes demand cleaning from pre-cleaning in memory management?
What is the initial setting of the use bit for an incoming page in the Clock algorithm?
What is the initial setting of the use bit for an incoming page in the Clock algorithm?
In the FIFO replacement policy, how is page order primarily determined?
In the FIFO replacement policy, how is page order primarily determined?
What is the primary goal of the LRU page replacement algorithm?
What is the primary goal of the LRU page replacement algorithm?
In a scenario with three initially empty frames, which page would be replaced first when a new page needs to be loaded in LRU?
In a scenario with three initially empty frames, which page would be replaced first when a new page needs to be loaded in LRU?
How does LRU compare to FIFO with respect to page faults?
How does LRU compare to FIFO with respect to page faults?
Which of the following statements about LRU is correct?
Which of the following statements about LRU is correct?
What assumption is made regarding the number of frames when implementing LRU based on the provided content?
What assumption is made regarding the number of frames when implementing LRU based on the provided content?
Which page replacement algorithm would likely incur the most faults in the given scenario?
Which page replacement algorithm would likely incur the most faults in the given scenario?
In the context of memory management, what does 'page fault' refer to?
In the context of memory management, what does 'page fault' refer to?
In a FIFO page replacement algorithm with 3 frames, which page is replaced first when a page fault occurs?
In a FIFO page replacement algorithm with 3 frames, which page is replaced first when a page fault occurs?
How many page faults occur in the FIFO algorithm with 3 frames for the page stream A; B; C; D; A; B; E?
How many page faults occur in the FIFO algorithm with 3 frames for the page stream A; B; C; D; A; B; E?
What is the total number of transfers made when using 4 frames in the FIFO page replacement algorithm?
What is the total number of transfers made when using 4 frames in the FIFO page replacement algorithm?
In the context of the given page stream with 4 frames, which page remained in memory the longest before being replaced?
In the context of the given page stream with 4 frames, which page remained in memory the longest before being replaced?
When using 3 frames, which of the following pages is replaced last in the FIFO algorithm before repeating the cycle?
When using 3 frames, which of the following pages is replaced last in the FIFO algorithm before repeating the cycle?
What is a major characteristic of the FIFO page replacement policy?
What is a major characteristic of the FIFO page replacement policy?
What is the maximum number of distinct pages that can be held in memory at once when using 3 frames?
What is the maximum number of distinct pages that can be held in memory at once when using 3 frames?
Which page would remain in memory the longest in the FIFO algorithm with 4 frames for the provided page stream?
Which page would remain in memory the longest in the FIFO algorithm with 4 frames for the provided page stream?
What does the Least Recently Used (LRU) replacement policy do?
What does the Least Recently Used (LRU) replacement policy do?
Which replacement algorithm treats page frames as a circular buffer?
Which replacement algorithm treats page frames as a circular buffer?
In the Clock replacement algorithm, what is the purpose of the use bit?
In the Clock replacement algorithm, what is the purpose of the use bit?
What happens when a page with a use bit of 1 is encountered in the Clock algorithm?
What happens when a page with a use bit of 1 is encountered in the Clock algorithm?
Which of the following statements about the Optimal Replacement algorithm is true?
Which of the following statements about the Optimal Replacement algorithm is true?
What is one drawback of the First-In-First-Out (FIFO) algorithm?
What is one drawback of the First-In-First-Out (FIFO) algorithm?
What is a potential issue encountered with the LRU replacement policy?
What is a potential issue encountered with the LRU replacement policy?
Which algorithm is noted for performing relatively poorly despite being simple to implement?
Which algorithm is noted for performing relatively poorly despite being simple to implement?
What occurs if all frames in the Clock replacement algorithm have a use bit of 1?
What occurs if all frames in the Clock replacement algorithm have a use bit of 1?
Which of the following best describes a benefit of using the Clock replacement algorithm?
Which of the following best describes a benefit of using the Clock replacement algorithm?
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Study Notes
Replacement Policy Algorithms
- Optimal Algorithm replaces page that is least likely to be referenced in the near future, it has the best performance.
- Least Recently Used (LRU) Algorithm replaces the page in memory that has not been referenced for the longest time, it's based on the principle of locality.
- First-In-First-Out (FIFO) Algorithm is the simplest to implement but performs relatively poorly.
- Clock Algorithm requires an additional bit associated with each frame, called the use bit.
- Initial Value of Use bit: 1, when the page is first loaded.
- Subsequent Use Bit: 1, when the page is referenced.
- Value when Page is Replaced: Pointer is moved to the next frame.
- Scan for Replacement Page: OS looks for a page with use bit = 0 and the page with the use bit = 1 is reset to 0.
- If All Use Bits = 1: The pointer cycles through the buffer, sets all use bits to 0, and replaces the page in the original position.
- The Clock Algorithm is considered a compromise between simplicity and performance.
Cleaning Policy
- Cleaning Policy determines when a modified page should be written out to secondary memory.
- Two alternatives to cleaning:
- Demand Cleaning: A page is only written out to secondary memory when it has been selected for replacement.
- Pre-Cleaning: Pages can be written out in batches, improving performance.
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