📝 Multilevel Feedback Queue Algorithm (55 MCQs)

📖 From Operating System • 6. CPU Scheduling • 55 questions available

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What is Multilevel Feedback Queue Algorithm?

Definition:
MLFQ extends multilevel queuing by allowing processes to move between queues based on their CPU-burst characteristics, using parameters like number of queues $N$ , quantum $q_i$ , and promotion/demotion rules.

Example:
A new process starts in Q0 ( $q=8ms$ ); if it doesn't finish in one quantum, it drops to Q1 ( $q=16ms$ ); if it releases CPU early due to I/O, it may be promoted back to Q0.

Reason:
MLFQ automatically adapts to process behavior, favoring short/interactive jobs while preventing starvation of CPU-bound jobs, making it the most general and widely used scheduling approach.

Easy

Medium

Hard

📝 All Multilevel Feedback Queue Algorithm MCQs

Q1. What is the key difference between multilevel queue and multilevel feedback queue scheduling?

A.Multilevel feedback queue has more queues

B.Multilevel feedback queue allows processes to move between queues ✅

C.Multilevel queue allows process movement

D.There is no difference

💡 Difficulty: easy | ✅ Correct: B

📖 Explanation: The key difference is that multilevel feedback queue scheduling allows processes to move between queues, while multilevel queue scheduling permanently assigns processes to a queue. This dynamic movement provides greater flexibility in handling varying process behavior.

Q2. Why might a process be moved to a lower-priority queue in multilevel feedback queue scheduling?

A.It has high priority

B.It uses too much CPU time ✅

C.It has short CPU bursts

D.It is I/O-bound

💡 Difficulty: easy | ✅ Correct: B

📖 Explanation: A process that uses too much CPU time is moved to a lower-priority queue. This prevents CPU-bound processes from monopolizing the CPU and ensures that I/O-bound and interactive processes, which have shorter bursts, remain in higher-priority queues.

Q3. What is the purpose of moving a process that waits too long to a higher-priority queue?

A.To increase its CPU burst

B.To prevent starvation ✅

C.To reduce its priority

D.To terminate the process

💡 Difficulty: easy | ✅ Correct: B

📖 Explanation: Moving a process that waits too long to a higher-priority queue is a form of aging that prevents starvation. This ensures that even low-priority processes eventually get CPU time, addressing the indefinite blocking problem.

Q4. In the three-queue example (Q0, Q1, Q2), what is the time quantum for processes in queue 0?

A.16 milliseconds

B.8 milliseconds ✅

C.FCFS

D.4 milliseconds

💡 Difficulty: easy | ✅ Correct: B

📖 Explanation: In the three-queue example, processes in queue 0 are given a time quantum of 8 milliseconds. This short quantum allows quick turnaround for short CPU bursts, favoring interactive and I/O-bound processes.

Q5. In the three-queue example, what is the time quantum for processes in queue 1?

A.8 milliseconds

B.16 milliseconds ✅

C.FCFS

D.32 milliseconds

💡 Difficulty: easy | ✅ Correct: B

📖 Explanation: Processes in queue 1 are given a time quantum of 16 milliseconds. This is longer than queue 0's quantum, reflecting that these processes have used more CPU time and are given larger slices before being potentially demoted.

Q6. In the three-queue example, which scheduling algorithm is used for queue 2?

A.Round-Robin

B.SJF

C.FCFS ✅

D.Priority

💡 Difficulty: easy | ✅ Correct: C

📖 Explanation: Queue 2 uses FCFS scheduling. Processes that sink to queue 2 (long CPU bursts) are served in FCFS order using any CPU cycles left over from higher-priority queues 0 and 1. This treats long-running processes in the simplest way.

Q7. What is the priority order of queues in the three-queue feedback example?

A.Q2, Q1, Q0

B.Q0, Q1, Q2 ✅

C.Q1, Q0, Q2

D.All equal

💡 Difficulty: easy | ✅ Correct: B

📖 Explanation: The priority order is Q0 highest, then Q1, then Q2 lowest. The scheduler first executes all processes in Q0, then Q1 when Q0 is empty, and finally Q2 when both Q0 and Q1 are empty. This gives highest priority to the shortest CPU bursts.

Q8. What happens when a process in queue 0 does not finish within its time quantum?

A.It is terminated

B.It is moved to the tail of queue 1 ✅

C.It continues running

D.It is moved to queue 2

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: If a process in queue 0 does not finish within the 8ms quantum, it is moved to the tail of queue 1. This demotion reflects that the process needs more CPU time than a short burst, so it is placed in a lower-priority queue with a longer quantum.

Q9. What happens when a process in queue 1 does not finish within its time quantum?

A.It is moved to queue 0

B.It is moved to the tail of queue 2 ✅

C.It continues running

D.It is terminated

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: If a process in queue 1 does not finish within the 16ms quantum, it is preempted and put into queue 2. This demotion indicates the process has a long CPU burst and will run in FCFS order in the lowest-priority queue when higher-priority queues are empty.

Q10. What is the primary advantage of allowing processes to move between queues?

A.Reduced scheduling overhead

B.Increased flexibility in handling varying process behavior ✅

C.Simpler implementation

D.More memory is available

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: Allowing processes to move between queues provides flexibility. Processes that start with short bursts but become CPU-bound can be demoted, while processes that wait too long can be aged to higher-priority queues. This adaptability improves overall system performance.

Q11. What is the primary disadvantage of multilevel feedback queue scheduling?

A.It is too simple

B.It is the most complex CPU-scheduling algorithm ✅

C.It causes starvation

D.It cannot handle I/O-bound processes

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: Multilevel feedback queue scheduling is the most complex CPU-scheduling algorithm. Defining the best scheduler requires selecting appropriate values for many parameters (number of queues, algorithms, upgrade/demote policies, and entry rules), making it challenging to configure optimally.

Q12. In the three-queue example, what type of process is most likely to remain in queue 0?

A.CPU-bound processes

B.I/O-bound and interactive processes ✅

C.Long-running batch processes

D.System processes

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: I/O-bound and interactive processes with short CPU bursts (8ms or less) are most likely to remain in queue 0. They get CPU quickly, finish their burst, and go to I/O. This prioritization benefits interactive performance and overall system responsiveness.

Q13. What happens if a process is in queue 1 and a process arrives for queue 0?

A.The queue 1 process continues

B.The queue 1 process is preempted ✅

C.The queue 0 process waits

D.Both processes run

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: A process arriving for queue 0 will preempt a process in queue 1 because queue 0 has higher priority. This ensures that even if queue 1 is running, new short-burst processes receive immediate attention.

Q14. What happens if a process is in queue 2 and a process arrives for queue 1?

A.The queue 2 process continues

B.The queue 2 process is preempted ✅

C.The queue 1 process waits

D.Both processes run

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: A process arriving for queue 1 will preempt a process in queue 2 because queue 1 has higher priority. This ensures that medium-burst processes take priority over long-burst processes in FCFS.

Q15. What is the time quantum range for processes that need more than 8ms but less than 24ms in the three-queue example?

A.8-16ms

B.16-24ms ✅

C.0-8ms

D.24-32ms

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: Processes needing more than 8ms but less than 24ms are served in queue 1 with a 16ms quantum. They may need one or two quanta in queue 1 before completing. This provides reasonable service for medium-length bursts.

Q16. Which processes get the highest priority in the three-queue multilevel feedback scheduler?

A.Processes with CPU bursts of 8ms or less ✅

B.Processes with CPU bursts of 16ms or less

C.Processes in queue 2

D.Long-running processes

💡 Difficulty: medium | ✅ Correct: A

📖 Explanation: Processes with CPU bursts of 8ms or less get the highest priority because they are placed in queue 0. They quickly get the CPU, finish their burst, and go to I/O. This prioritization reduces response time for short, interactive processes.

Q17. What happens to a process that does not complete in queue 0 or queue 1 in the three-queue example?

A.It is terminated

B.It sinks to queue 2 and runs FCFS ✅

C.It moves back to queue 0

D.It gets a higher priority

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: A process that does not complete in queue 0 (8ms quantum) or queue 1 (16ms quantum) sinks to queue 2. In queue 2, processes are run on an FCFS basis using any CPU cycles left over from queues 0 and 1. This provides service to long-running processes.

Q18. What is the purpose of moving a process that waits too long to a higher-priority queue?

A.To punish the process

B.To prevent starvation ✅

C.To reduce its CPU usage

D.To simplify scheduling

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: Moving a process that waits too long to a higher-priority queue is a form of aging. This prevents starvation by ensuring that even low-priority processes eventually get CPU time, addressing the indefinite blocking problem common in priority-based systems.

Q19. Which of the following is NOT a parameter that defines a multilevel feedback queue scheduler?

A.The number of queues

B.The scheduling algorithm for each queue

C.The memory allocation for each process ✅

D.The method to determine when to upgrade/demote a process

💡 Difficulty: medium | ✅ Correct: C

📖 Explanation: Memory allocation is not a scheduling parameter. The key parameters are: number of queues, scheduling algorithm for each queue, upgrade/demote methods, and entry queue determination. These parameters define the scheduler's behavior and complexity.

Q20. What makes multilevel feedback queue scheduling the most general CPU-scheduling algorithm?

A.It uses only one queue

B.It can be configured to match a specific system design ✅

C.It is the simplest algorithm

D.It requires no parameters

💡 Difficulty: medium | ✅ Correct: B

📖 Explanation: Multilevel feedback queue scheduling is the most general because it can be configured to match a specific system under design. By selecting appropriate values for all parameters (number of queues, algorithms, upgrade/demote policies), it can be adapted to various system requirements.

Q21. Why does the multilevel feedback queue scheduler leave I/O-bound processes in higher-priority queues?

A.They use less memory

B.They have short CPU bursts and need good response time ✅

C.They have higher priority

D.They are system processes

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: I/O-bound processes have short CPU bursts and need good response time to handle I/O operations efficiently. Placing them in higher-priority queues ensures they get CPU quickly when they need it, improving overall system performance and I/O throughput.

Q22. In the three-queue example, what happens to a process that needs exactly 8ms of CPU time?

A.It runs in queue 0 and completes ✅

B.It is moved to queue 1

C.It runs in queue 2

D.It is terminated

💡 Difficulty: hard | ✅ Correct: A

📖 Explanation: A process with exactly 8ms CPU burst runs in queue 0 within its 8ms quantum and completes. It is not moved to another queue. The scheduler only moves processes that do NOT finish within their quantum, so exact completion stays in the current queue.

Q23. What is the maximum CPU burst that a process can complete in queue 1 in the three-queue example?

A.8ms

B.16ms

C.24ms ✅

D.32ms

💡 Difficulty: hard | ✅ Correct: C

📖 Explanation: A process in queue 1 gets a 16ms quantum. If it has already used 8ms in queue 0 and then runs for up to 16ms in queue 1, the maximum burst it can complete before being demoted is 8 + 16 = 24ms. This explains why processes needing 8-24ms are served in queues 0 and 1.

Q24. Why might a multilevel feedback queue scheduler be preferred over a multilevel queue scheduler?

A.It is simpler to implement

B.It adapts to changing process behavior ✅

C.It has lower overhead

D.It requires fewer queues

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: Multilevel feedback queue scheduling adapts to changing process behavior by allowing processes to move between queues based on their CPU usage patterns. This flexibility makes it superior to multilevel queue scheduling for systems with diverse and dynamic workloads.

Q25. What is the primary challenge in implementing a multilevel feedback queue scheduler?

A.Memory requirements

B.Configuring the parameters optimally ✅

C.Context switch overhead

D.Process creation time

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: The primary challenge is configuring the scheduler parameters optimally. With many parameters (number of queues, algorithms, quantum sizes, upgrade/demote policies), finding the best configuration for a specific system requires careful analysis and tuning.

Q26. In the three-queue example, what is the priority of a process that is currently running in queue 2?

A.Highest priority

B.Lowest priority among running processes ✅

C.Same as queue 0

D.Higher than queue 1

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: Queue 2 has the lowest priority. A process in queue 2 runs only when queues 0 and 1 are empty. It can be preempted by any process arriving in queue 0 or queue 1. This ensures that short-burst processes always take precedence over long-running processes.

Q27. What is the effect of using a shorter time quantum in queue 0 compared to queue 1?

A.It favors long-running processes

B.It favors short CPU bursts ✅

C.It reduces context switching

D.It simplifies scheduling

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: A shorter quantum in queue 0 (8ms) favors short CPU bursts by giving them quick service and priority. Processes with short bursts complete before the quantum expires, while longer processes are demoted to queue 1. This prioritization benefits interactive and I/O-bound processes.

Q28. How does the multilevel feedback queue scheduler prevent starvation?

A.By terminating long-running processes

B.By using aging to move processes to higher-priority queues ✅

C.By using only one queue

D.By reducing the CPU time of all processes

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: Starvation is prevented through aging: processes that wait too long in lower-priority queues are moved to higher-priority queues. This ensures that even low-priority processes eventually get CPU time, addressing the indefinite blocking problem.

Q29. What type of processes sink to queue 2 in the three-queue example?

A.Interactive processes

B.I/O-bound processes

C.Long CPU-bound processes ✅

D.Short-burst processes

💡 Difficulty: hard | ✅ Correct: C

📖 Explanation: Long CPU-bound processes sink to queue 2. These are processes that require more than 24ms of CPU time (8ms in Q0 + 16ms in Q1) and are run on an FCFS basis. They receive the lowest priority and only run when higher-priority queues are empty.

Q30. What is the relationship between the time quantum and the priority level in the three-queue example?

A.Higher priority queues have larger quanta

B.Higher priority queues have smaller quanta ✅

C.All queues have equal quanta

D.Priority is unrelated to quantum

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: Higher priority queues have smaller quanta (Q0=8ms, Q1=16ms). This is intentional: short-burst processes get small quanta and quick service, while processes that need more CPU time get larger quanta but lower priority, reflecting their different scheduling needs.

Q31. Which scheduling algorithm is the most general and can be configured to match a specific system design?

A.FCFS

B.Round-Robin

C.Multilevel feedback queue ✅

D.SJF

💡 Difficulty: hard | ✅ Correct: C

📖 Explanation: Multilevel feedback queue scheduling is the most general because it can be configured with various parameters to match specific system requirements. It combines features of multiple algorithms, making it highly adaptable but also complex to configure optimally.

Q32. In the three-queue example, what happens when a process in queue 2 is running and a process arrives for queue 1?

A.The queue 2 process continues

B.The queue 2 process is preempted ✅

C.The queue 1 process waits

D.Both processes run

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: When a process arrives for queue 1 while queue 2 is running, the queue 2 process is preempted. Queue 1 has higher priority than queue 2, so the newly arrived process runs immediately. The queue 2 process resumes when queues 0 and 1 are empty.

Q33. What is the maximum CPU burst that can be completed in queue 0 in the three-queue example?

A.8ms ✅

B.16ms

C.24ms

D.Unlimited

💡 Difficulty: hard | ✅ Correct: A

📖 Explanation: The maximum CPU burst that can be completed in queue 0 is exactly 8ms. A process with a CPU burst of 8ms or less completes in queue 0. If it needs more than 8ms, it is moved to the tail of queue 1 after its quantum expires.

Q34. What is the purpose of the three-queue structure in the multilevel feedback queue example?

A.To make scheduling simpler

B.To separate processes by CPU burst length ✅

C.To reduce memory usage

D.To eliminate context switching

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: The three-queue structure separates processes by CPU burst length: queue 0 for very short bursts (≤8ms), queue 1 for medium bursts (8-24ms), and queue 2 for long bursts (>24ms). This separation allows different scheduling treatments for different burst patterns.

Q35. How does the multilevel feedback queue scheduler treat interactive processes differently from CPU-bound processes?

A.It gives them lower priority

B.It keeps them in higher-priority queues ✅

C.It moves them to queue 2

D.It treats them the same

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: Interactive processes with short CPU bursts are kept in higher-priority queues (Q0 and Q1). This ensures they get quick CPU service when they need it, providing good response time. CPU-bound processes are demoted to lower-priority queues.

Q36. What is the effect of moving a CPU-bound process to a lower-priority queue?

A.It increases its priority

B.It reduces its CPU time

C.It allows interactive processes to have better response time ✅

D.It terminates the process

💡 Difficulty: hard | ✅ Correct: C

📖 Explanation: Moving CPU-bound processes to lower-priority queues allows interactive and I/O-bound processes in higher-priority queues to get quick service. This prevents CPU-bound processes from monopolizing the CPU and improves overall system responsiveness.

Q37. What determines which queue a process enters in a multilevel feedback queue scheduler?

A.The process's memory requirements

B.The method defined for that scheduler ✅

C.The process's arrival time

D.The number of open files

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: The entry queue is determined by the method defined for that particular scheduler. This is one of the key parameters that must be configured. Typically, new processes enter the highest-priority queue, but the specific entry method can vary based on system design.

Q38. Why might a process that waits too long in a lower-priority queue be moved to a higher-priority queue?

A.To punish the process

B.To provide aging and prevent starvation ✅

C.To increase its CPU burst

D.To reduce context switching

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: Moving a waiting process to a higher-priority queue is a form of aging. This prevents starvation by ensuring that even processes initially classified as long-running eventually get CPU time. It guarantees that no process waits indefinitely.

Q39. What is the advantage of using FCFS in queue 2 of the three-queue example?

A.It provides the best response time

B.It is simple for long-running processes ✅

C.It minimizes average waiting time

D.It prevents starvation

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: FCFS is used in queue 2 because it is simple and suitable for long-running processes. These processes don't need interactive response, so FCFS provides adequate service with low overhead. The complexity of RR or SJF would be wasted on processes that run infrequently.

Q40. What happens to a process in queue 1 if a process arrives for queue 0 in the three-queue example?

A.The queue 1 process continues

B.The queue 1 process is preempted ✅

C.The queue 0 process waits

D.Both processes share CPU

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: A process arriving for queue 0 preempts any process in queue 1. This is because queue 0 has absolute priority over queue 1. The queue 1 process resumes when queue 0 becomes empty, ensuring highest priority for the shortest bursts.

Q41. What is the total CPU time available for a process before it sinks to queue 2 in the three-queue example?

A.8ms

B.16ms

C.24ms ✅

D.32ms

💡 Difficulty: hard | ✅ Correct: C

📖 Explanation: A process gets 8ms in queue 0 and if it doesn't complete, 16ms in queue 1. If it still doesn't complete (total 24ms), it sinks to queue 2. This threshold separates medium bursts (8-24ms) from long bursts (>24ms).

Q42. How does the multilevel feedback queue scheduler adapt to processes with varying CPU burst lengths?

A.It uses the same quantum for all processes

B.It moves processes between queues based on their behavior ✅

C.It assigns fixed priorities

D.It ignores burst length variation

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: The scheduler adapts by moving processes between queues based on their behavior. Processes with short bursts stay in high-priority queues, those needing more time are demoted, and those waiting too long are promoted. This dynamic adaptation handles varying burst lengths effectively.

Q43. What is the purpose of using different time quanta in different queues?

A.To simplify implementation

B.To match scheduling to burst length characteristics ✅

C.To reduce memory usage

D.To increase context switching

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: Different time quanta in different queues match scheduling to burst length characteristics. Short bursts get smaller quanta (quick turnaround), while longer bursts get larger quanta (fewer context switches). This differentiation improves efficiency for each process type.

Q44. What happens if a process in queue 2 is running and a process arrives for queue 0?

A.The queue 2 process continues

B.The queue 2 process is preempted ✅

C.The queue 0 process waits

D.Both processes run

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: When a process arrives for queue 0 while queue 2 is running, the queue 2 process is immediately preempted. Queue 0 has the highest priority, so the newly arrived process runs. The queue 2 process resumes only when queues 0 and 1 are empty.

Q45. What is the primary reason for the complexity of multilevel feedback queue scheduling?

A.It requires too much memory

B.It has many configurable parameters ✅

C.It uses multiple queues

D.It requires frequent context switches

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: The complexity arises from having many configurable parameters: number of queues, scheduling algorithms for each queue, upgrade/demote methods, and entry queue determination. Finding the optimal configuration for a specific system is challenging.

Q46. In the three-queue example, what is the priority of a process that has been demoted to queue 2?

A.Higher than queue 0

B.Higher than queue 1

C.Lower than queues 0 and 1 ✅

D.Equal to all queues

💡 Difficulty: hard | ✅ Correct: C

📖 Explanation: Queue 2 has the lowest priority. A process in queue 2 runs only when queues 0 and 1 are empty. This ensures that even long-running processes get service, but only after all higher-priority processes are done.

Q47. What type of processes benefit most from the three-queue multilevel feedback scheduler?

A.CPU-bound processes

B.Interactive and I/O-bound processes ✅

C.Batch processes

D.System processes

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: Interactive and I/O-bound processes benefit most because they are kept in high-priority queues (Q0 and Q1) and get quick CPU service. This reduces response time and improves overall system interactivity, which is the main goal of such schedulers.

Q48. What is the effect of the multilevel feedback queue scheduler on CPU-bound processes?

A.They get highest priority

B.They sink to lower-priority queues ✅

C.They complete quickly

D.They never get CPU time

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: CPU-bound processes sink to lower-priority queues (Q2 in the example). This prevents them from interfering with interactive processes. They still get CPU time when higher-priority queues are empty, ensuring they eventually complete.

Q49. What is the relationship between a process's CPU burst length and its queue assignment in the three-queue example?

A.Burst length determines initial queue but not movement

B.Burst length determines movement to lower queues ✅

C.Burst length is irrelevant

D.All processes start in queue 2

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: Burst length determines movement to lower queues. Processes that exceed their quantum in Q0 move to Q1, and those exceeding Q1's quantum move to Q2. This dynamic movement based on actual burst length adapts scheduling to process behavior.

Q50. Why might a system designer choose a multilevel feedback queue scheduler over simpler algorithms?

A.It is easier to implement

B.It provides better performance for diverse workloads ✅

C.It requires fewer parameters

D.It has lower overhead

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: Multilevel feedback queue scheduling provides better performance for diverse workloads because it can adapt to different process behaviors. It combines the benefits of multiple algorithms and can be tuned for specific system requirements, making it superior despite its complexity.

Q51. What is the primary design goal of the three-queue example in multilevel feedback scheduling?

A.To minimize memory usage

B.To provide good service to both short and long processes ✅

C.To eliminate context switching

D.To simplify the scheduler

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: The design goal is to provide good service to all process types. Short processes get quick service in Q0, medium processes get good service in Q1, and long processes get service in Q2. This balances the needs of different processes, though at the cost of complexity.

Q52. What happens to a process that completes its CPU burst in queue 0?

A.It moves to queue 1

B.It is removed from the system ✅

C.It moves to queue 2

D.It continues running

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: If a process completes its CPU burst in queue 0, it is removed from the system (it goes to its next I/O burst or terminates). It does not move to another queue because it has finished its CPU work. Only processes that do NOT finish within the quantum are moved.

Q53. What is the significance of the multilevel feedback queue scheduler being the most general CPU-scheduling algorithm?

A.It can replace all other algorithms

B.It can be configured to implement many scheduling policies ✅

C.It is the simplest to use

D.It requires no tuning

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: Being the most general means it can be configured to implement many scheduling policies. By setting parameters appropriately, it can mimic FCFS, RR, SJF, or priority scheduling. This flexibility makes it powerful but complex to configure optimally.

Q54. In the three-queue example, what happens if a process in queue 0 does not finish within 8ms?

A.It is moved to queue 1 with a 16ms quantum ✅

B.It is moved to queue 2 immediately

C.It continues running in queue 0

D.It is terminated

💡 Difficulty: hard | ✅ Correct: A

📖 Explanation: If a process in queue 0 does not finish within 8ms, it is moved to the tail of queue 1. In queue 1, it gets a longer quantum of 16ms, reflecting that it needs more CPU time. This demotion ensures short-burst processes are prioritized.

Q55. What is the purpose of the aging mechanism in multilevel feedback queue scheduling?

A.To reduce CPU usage

B.To prevent starvation ✅

C.To increase context switching

D.To simplify scheduling

💡 Difficulty: hard | ✅ Correct: B

📖 Explanation: Aging prevents starvation by moving processes that wait too long to higher-priority queues. This ensures that even low-priority processes eventually get CPU time, addressing the indefinite blocking problem common in priority-based scheduling.

🔗 Related Topics (MCQs)

📝 CPU Scheduling Basic Concepts MCQs 📝 CPU I/O Burst Cycle MCQs 📝 CPU Scheduler in Operating System MCQs 📝 Preemptive Scheduling in Operating System MCQs 📝 Dispatcher in CPU Scheduling MCQs

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