CPU Scheduling

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### CPU Scheduling Overview:

Imagine you're a teacher assigning tasks to your students during class time. Your goal is to make sure everyone gets a fair chance to contribute while keeping the class productive and engaged.


### CPU Scheduling Functions:

1. **Process Management:** This is like managing a queue of tasks. You decide which student (process) gets to speak (execute) next.

   

2. **Resource Allocation:** You ensure each student (process) gets a fair share of speaking time (CPU time).

   

3. **Performance Optimization:** You aim to keep the class running smoothly by minimizing disruptions (context switches) and maximizing participation (CPU utilization).


### CPU Scheduling Operation:

You manage the class by:

1. **Process Arrival:** When a student is ready to speak, they join the queue.

   

2. **Scheduling Decision:** You choose which student speaks next based on various factors like importance (priority) or task difficulty (CPU burst time).

   

3. **CPU Execution:** The chosen student speaks until their turn is over or they're interrupted (preempted) by a more urgent task.

   

4. **Context Switching:** When one student finishes speaking, you prepare for the next by saving their progress and loading the next student's details.


### CPU Scheduling Challenges:

1. **Optimization Trade-offs:** Balancing fairness, efficiency, and responsiveness can be like juggling priorities in a busy classroom.

   

2. **Resource Contention:** It's like managing group projects where everyone needs access to limited resources without anyone feeling left out.

   

3. **Real-Time Constraints:** Just as meeting project deadlines is crucial, ensuring timely responses in critical systems is essential.


### CPU Scheduling Criteria:

1. **CPU Utilization:** You want to keep all students engaged to make the most of class time.

   

2. **Throughput:** It's like measuring how many tasks your class can complete in a set time.

   

3. **Turnaround Time:** This is how long it takes from assigning a task to completing it.

   

4. **Waiting Time:** Like how long students wait for their turn to speak.

   

5. **Response Time:** It's the time between asking a question and getting an answer.


### CPU Scheduling Algorithms:

1. **FCFS:** Giving tasks in the order they're received, like handling emails as they come in.

   

2. **SJN/SJF:** Prioritizing short tasks first, similar to completing quick errands before longer chores.

   

3. **RR:** Allowing each task a fixed time before moving to the next, like rotating tasks in a group project.

   

4. **Priority Scheduling:** Handling urgent tasks first, similar to addressing important emails immediately.

   

5. **Multilevel Queue:** Sorting tasks into different categories, such as urgent and non-urgent, and handling each group separately.


### Preemptive vs. Non-preemptive Scheduling:

1. **Preemptive:** Interrupting a task to handle a more urgent one, like pausing a video to answer an important call.

   

2. **Non-preemptive:** Letting tasks finish before starting new ones, similar to waiting for one task to complete before starting the next.


### Long-Term Scheduler:

Imagine admitting students to your class. You decide how many students can join based on available space and resources.


### Medium-Term Scheduler:

It's like deciding when students take breaks. You manage who stays in the classroom and who takes a break to keep everyone refreshed.


### Short-Term Scheduler:

Deciding who speaks next during class discussions, considering factors like participation and urgency.


These analogies should help you grasp CPU scheduling concepts more easily by relating them to everyday scenarios!

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