Standard: CPU
In this in class activity, we use grade school worksheets as a vehicle for learning all about job timing!
Estimated Time: 75 minutes
Welcome back to elementary school! You'll complete math worksheets under different scheduling system constraints to experience how CPUs schedule tasks.
3 Stages:
You'll feel the frustrations of context switching, deadline pressure, and coordination overhead firsthand!
Any simple math worksheets will work! Choose something easy enough to be fast-paced but challenging enough to keep things manageable.
Recommended resource: Super Teacher Worksheets
Pro Tip: If possible, give each student a different colored pen/pencil. This helps visualize context switching in the Interactive stage!
This activity has 3 stages (~15 minutes each):
After each stage: count scores, reflect, and discuss!
Be the first to set the record!
Complete this activity and add your class stats to the leaderboard.
You'll act as the scheduler controlling task distribution!
Maximize throughput - Complete as many worksheets as possible!
Batch systems prioritize getting the most work done in the least time. High hardware utilization, high job throughput, minimal restrictions.
You (the instructor) are the scheduler. Students are "CPU cores" executing tasks.
You MUST:
You CANNOT:
You CAN:
You can adjust the activity to show interesting patterns:
Think About It: This models a simple batch processing system. What happens if some "cores" (students) are faster than others? How does job length affect throughput?
Maximize responsiveness - Make progress on many jobs at once!
Interactive systems prioritize making the device feel "snappy" and responsive. Less focus on overall throughput, more focus on ensuring all jobs make progress.
You (the instructor) control the time quanta with a bell.
Teams now have two roles:
As a Worker:
As a Runner:
Everyone:
Think About It: How does frequent context switching affect productivity? Do shorter time quanta feel more "responsive" even if throughput drops? Notice the different colored pens on each worksheet!
Meet deadlines - Complete work before the deadline, or lose points!
Real-time systems prioritize meeting deadlines over throughput or responsiveness. Used in critical applications where "late" = "failure".
You (the instructor) control deadlines with a bell. Teams self-schedule!
You MUST:
You CANNOT:
You CAN:
Teams might:
Think About It: How did deadline pressure change your strategy? Did your team take risks or play it safe? How does this relate to embedded systems (pacemakers, antilock brakes) where missing deadlines can be dangerous?
After all stages are complete, gather everyone and discuss these questions. Connect student experiences back to hardware/software concepts!
Q1: What was your strategy in the Batch System? Did you feel successful? Would being able to choose between easy/hard worksheets have changed your approach?
Q2: What changes would have helped your team complete more tasks? (More people? Better tools? More time? Different job sizes?)
Q3: What does the "perfect" batch of jobs look like for a Batch System? (Think about job variety, complexity, and team size)
Q4: What was your strategy as a worker vs as a runner? How did the bell affect your decisions? Did you wish teammates did things differently?
Q5: Were you ever relieved when the bell rang? Or was it always frustrating? How did your feelings change as time quanta got shorter or longer?
Q6: How many different colors did you see on completed worksheets? What was common between worksheets with many colors vs few colors? How did quality differ?
This visualizes context switching overhead!
Q7: What does the "perfect" batch of jobs look like for an Interactive System? Consider both workers and runners.
Q8: What was your team's strategy? How did the deadline bell affect decisions? What would you do differently?
Q9: Did you make decisions that led to high/low point loss? Did you have enough time to strategize? Would you change your risk tolerance?
Q10: When deadlines got shorter or longer, how did your strategy change? Did you assign roles or have people specialize?
Q11: What does the "perfect" batch of jobs look like for a Real-Time System? (Consider deadline timing and job predictability)
Q12: Any final frustrations, insights, strategies, or recommendations? Try to map your experience onto hardware or software concepts we've learned!
Batch Systems (FCFS):
Interactive Systems (Round Robin):
Real-Time Systems (EDF):
Participation-based - No winner or loser! Just engage, strategize, and participate in the discussion.
Couldn't make it to class? You can make up the points by completing this alternate assignment!
Watch this excellent video from Core Dumped about CPU scheduling. George explains scheduling algorithms and their trade-offs beautifully.
While watching, keep the 3 system types in mind: Batch, Interactive, and Real-Time.
Video: The Fancy Algorithms That Make Your Computer Feel Smoother
Submit a PDF with your answers to Brightspace:
Q1: What specific scheduling algorithms mentioned in the video would be most appropriate for each system type (Batch, Interactive, and Real-Time), and why? Provide specific application examples.
Note: Real-Time algorithms aren't discussed directly - consider which algorithms would work best.
Q2: The video mentions metrics like turnaround time, waiting time, and throughput. How does the relative importance of these metrics shift across Batch, Interactive, and Real-Time systems?
Q3: Suppose you're designing an OS for a hospital's medical equipment. What equipment would you classify as batch, interactive, or real-time? Justify your choices and suggest appropriate scheduling techniques.
Q4: Compare and contrast how starvation might occur in each system type. How do scheduling algorithms for each type prevent starvation?
Q5: How might modern multi-core processors change the scheduling approaches discussed in the video? Consider how parallelism affects each system type differently.
Q6: The video discusses preemption. How does the importance and implementation of preemption differ between Batch, Interactive, and Real-Time systems?
Q7: The video mentions predicting CPU bursts. You don't need a mathematical solution, but consider all 3 system types - how would you predict CPU bursts for each? What factors would you consider?
Q8: Create a visual metaphor or analogy to explain the differences between the three system types to someone with no technical background. What would it be and why?
Submission: Upload your PDF to the relevant Brightspace assignment.