Multilevel queue scheduling in Operating Systems - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the sentence to define multilevel queue scheduling.

Operating Systems

In multilevel queue scheduling, processes are divided into [1] based on their characteristics.

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Athreads

Bqueues

Cprocessors

Dfiles

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing queues with threads or processors.

Thinking files are involved in scheduling.

Multilevel queue scheduling divides processes into separate queues based on their properties like priority or type.

2fill in blank

medium

Complete the sentence about the scheduling policy in multilevel queue scheduling.

Operating Systems

Each queue in multilevel queue scheduling has its own [1] to decide the order of process execution.

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Ascheduling algorithm

Bfile system

Cmemory size

Dnetwork protocol

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing scheduling algorithm with memory or network terms.

Thinking all queues share the same scheduling method.

Each queue uses its own scheduling algorithm to manage the processes within it.

3fill in blank

hard

Fix the error in the statement about process movement in multilevel queue scheduling.

Operating Systems

In multilevel queue scheduling, processes can [1] between queues during execution.

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Amove

Bjump

Cstay

Dswitch

Attempts:

3 left

💡 Hint

Common Mistakes

Assuming processes can move between queues like in multilevel feedback queue.

Confusing multilevel queue with other scheduling types.

In multilevel queue scheduling, processes stay in the queue they are assigned to; they do not move between queues.

4fill in blank

hard

Fill both blanks to complete the description of queue priority and scheduling.

Operating Systems

Higher priority queues are scheduled [1] than lower priority queues, and each queue uses [2] scheduling.

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Abefore

Bafter

Cround-robin

Dfirst-come-first-served

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up the order of priority scheduling.

Confusing scheduling algorithms used in queues.

Higher priority queues are scheduled before lower priority ones, and each queue can use first-come-first-served scheduling.

5fill in blank

hard

Fill all three blanks to complete the explanation of multilevel queue scheduling characteristics.

Operating Systems

Multilevel queue scheduling divides processes into [1], assigns each queue a [2], and does not allow [3] between queues.

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Aqueues

Bpriority

Cmovement

Dtime slices

Attempts:

3 left

💡 Hint

Common Mistakes

Thinking processes can move between queues.

Confusing priority with time slices.

It divides processes into queues, assigns each queue a priority, and does not allow movement of processes between queues.

Practice

1. What is the main characteristic of multilevel queue scheduling in operating systems?

easy

A. Processes move freely between queues during execution.

B. All processes are scheduled using the same method regardless of type.

C. Processes are divided into separate queues based on priority or type.

D. It uses a single queue with round-robin scheduling.

Solution

1. Step 1: Understand the queue division concept

   Multilevel queue scheduling divides processes into different queues based on their priority or type, such as system processes, interactive processes, etc.

2. Step 2: Recognize process movement rules

   Processes do not move between queues once assigned; each queue has its own scheduling method.

3. Final Answer:

   Processes are divided into separate queues based on priority or type. -> Option C

4. Quick Check:

   Multilevel queue = Separate queues by priority/type [OK]

Hint: Remember: fixed queues by type, no moving between them [OK]

Common Mistakes:

• Thinking processes can move between queues
• Assuming all queues use the same scheduling method
• Confusing with multilevel feedback queue

2. Which of the following is a correct statement about the scheduling method in multilevel queue scheduling?

easy

A. Processes are scheduled only after all queues are empty.

B. Each queue can have its own scheduling algorithm.

C. Scheduling is done randomly across all queues.

D. All queues must use the round-robin algorithm.

Solution

1. Step 1: Identify scheduling flexibility per queue

   In multilevel queue scheduling, each queue can use a different scheduling algorithm suitable for its process type.

2. Step 2: Eliminate incorrect options

   Options stating all queues use the same method or random scheduling are incorrect.

3. Final Answer:

   Each queue can have its own scheduling algorithm. -> Option B

4. Quick Check:

   Different queues = different scheduling methods [OK]

Hint: Each queue can pick its own scheduling style [OK]

Common Mistakes:

• Assuming all queues use round-robin
• Believing scheduling is random
• Thinking scheduling waits for all queues to empty

3. Consider a multilevel queue scheduling system with two queues: Queue 1 (high priority) uses FCFS, Queue 2 (low priority) uses Round Robin. If Queue 1 has 3 processes arriving first and Queue 2 has 2 processes arriving later, which queue's processes will be scheduled first?

medium

A. Queue 2 processes because Round Robin is fairer.

B. Both queues are scheduled alternately regardless of priority.

C. Queue 2 processes because they arrived later.

D. Queue 1 processes because it has higher priority.

Solution

1. Step 1: Identify priority order in multilevel queue

   Multilevel queue scheduling serves queues based on priority; higher priority queues are served before lower ones.

2. Step 2: Apply priority to given queues

   Queue 1 has higher priority, so its processes are scheduled first, regardless of scheduling method or arrival time of Queue 2.

3. Final Answer:

   Queue 1 processes because it has higher priority. -> Option D

4. Quick Check:

   Higher priority queue runs first [OK]

Hint: Higher priority queue always runs before lower ones [OK]

Common Mistakes:

• Thinking Round Robin queue runs first due to fairness
• Assuming arrival time overrides priority
• Believing queues are scheduled alternately

4. Identify the error in this description of multilevel queue scheduling: "Processes can move between queues if they wait too long in their current queue."

medium

A. This is incorrect; processes do not move between queues.

B. This is correct; processes move to higher priority queues.

C. This is correct; processes move to lower priority queues.

D. This is incorrect; processes move randomly between queues.

Solution

1. Step 1: Recall process movement rules in multilevel queue

   In multilevel queue scheduling, processes are assigned to a queue and remain there permanently.

2. Step 2: Compare with the given statement

   The statement says processes move between queues if waiting too long, which is false behavior for this scheduling type.

3. Final Answer:

   This is incorrect; processes do not move between queues. -> Option A

4. Quick Check:

   No process movement between queues [OK]

Hint: Processes stay fixed in their queue [OK]

Common Mistakes:

• Confusing with multilevel feedback queue
• Assuming aging causes queue changes
• Believing processes move randomly

5. In a multilevel queue scheduling system with three queues: System (highest priority), Interactive (medium priority), and Batch (lowest priority), how should CPU time be allocated if the System queue is always busy?

hard

A. System queue gets all CPU time; other queues wait until it is empty.

B. CPU time is shared equally among all queues regardless of priority.

C. Batch queue gets CPU time first to clear long jobs quickly.

D. Interactive queue preempts System queue when interactive tasks arrive.

Solution

1. Step 1: Understand priority handling in multilevel queue

   The CPU always serves the highest priority queue first until it is empty or blocked.

2. Step 2: Apply to given queues

   Since the System queue is highest priority and always busy, it will get all CPU time, causing other queues to wait.

3. Final Answer:

   System queue gets all CPU time; other queues wait until it is empty. -> Option A

4. Quick Check:

   Highest priority queue dominates CPU time [OK]

Hint: Highest priority queue runs exclusively if always busy [OK]

Common Mistakes:

• Assuming equal CPU sharing despite priority
• Thinking lower priority queues can preempt higher ones
• Believing batch jobs get priority to clear faster