Operating System CPU Scheduling: Convoy Effect Quiz and Flashcards

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Questions and Answers

What is the main responsibility of the CPU scheduler?

Handle I/O operations for processes

Switch the CPU from user mode to kernel mode

Allocate memory to processes

Select processes from memory to execute on the CPU (correct)

Under what conditions does the CPU scheduler make scheduling decisions?

Any state transition except for termination (correct)

Switching from running to waiting state only

Only when a process terminates

Switching from running to ready state only

What is the role of the dispatcher in CPU scheduling?

Gives control of the CPU to the selected process (correct)

Allocates memory to processes

Selects processes for execution on the CPU

Handles I/O operations for processes

When does non-preemptive scheduling occur?

When a process terminates Signup and view all the answers

What is the purpose of the CPU-I/O burst cycle in process execution?

To distribute CPU bursts among processes Signup and view all the answers

What is the maximum CPU utilization obtained with multiprogramming?

100% Signup and view all the answers

What is the optimization criteria for First-Come, First-Served (FCFS) scheduling?

Max waiting time Signup and view all the answers

Which of the following is true about the average waiting time under the FCFS policy?

It can vary substantially if the process CPU-burst times vary greatly Signup and view all the answers

What is the main disadvantage of the FCFS scheduling algorithm?

Long average waiting time Signup and view all the answers

In a dynamic situation with one CPU-bound process and many I/O-bound processes, what effect may result from using the FCFS scheduling algorithm?

A convoy effect as all other processes wait for the CPU-bound process Signup and view all the answers

What happens to the average waiting time under a FCFS policy if the process arrival order changes?

It decreases Signup and view all the answers

Which optimization criterion is NOT applicable to FCFS scheduling?

Min turnaround time Signup and view all the answers

What factor may lead to a substantial reduction in average waiting time under a FCFS policy?

Short CPU burst times Signup and view all the answers

What is the main advantage of the FCFS scheduling algorithm?

Ease of implementation and understanding Signup and view all the answers

In a dynamic situation with many I/O-bound processes, what may occur during FCFS scheduling?

A convoy effect as all processes move to I/O queues simultaneously Signup and view all the answers

What impact does a high variation in process CPU-burst times have on the average waiting time under a FCFS policy?

It increases the average waiting time Signup and view all the answers

Study Notes

CPU Scheduling

The main responsibility of the CPU scheduler is to allocate the CPU time to processes.
The CPU scheduler makes scheduling decisions under the following conditions:
- When a process switches from running to waiting state
- When a process switches from waiting to ready state
- When a process terminates

Dispatcher Role

The role of the dispatcher in CPU scheduling is to:
- Context switch (i.e., switch the CPU to another process)
- Perform process switching
- Save the state of the previously running process
- Restore the state of the newly scheduled process

Scheduling Types

Non-preemptive scheduling occurs when the operating system does not interrupt a process while it is executing.
CPU-I/O burst cycle: A process executes a CPU burst (uses the CPU), then performs I/O operations, and then repeats this cycle during its execution.

CPU Utilization

The maximum CPU utilization obtained with multiprogramming is typically 90% or higher.

First-Come, First-Served (FCFS) Scheduling

Optimization criterion: Minimize average waiting time.
Average waiting time under the FCFS policy:
- Increases as the process arrival order changes
- May be significantly affected by a high variation in process CPU-burst times
Main disadvantage of the FCFS scheduling algorithm: It can cause convoy effect (many I/O-bound processes waiting for a CPU-bound process).
Main advantage: Simple to implement.
In a dynamic situation with one CPU-bound process and many I/O-bound processes, the FCFS scheduling algorithm may cause the CPU-bound process to monopolize the CPU.
In a dynamic situation with many I/O-bound processes, the FCFS scheduling algorithm may cause many I/O-bound processes to wait for the completion of a CPU-bound process.

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Description

Test your knowledge of CPU scheduling basics in operating systems with this quiz. Questions cover concepts like scheduling criteria, algorithms, multiple-processor scheduling, real-time scheduling, and algorithm evaluation.

Operating System CPU Scheduling Basics Quiz