Thrashing and working set model in Operating Systems - Mini Project: Build & Apply

Understanding Thrashing and the Working Set Model

📖 Scenario: You are learning about how operating systems manage memory. Sometimes, a computer slows down because it spends too much time moving data between memory and disk. This is called thrashing. To understand this better, you will create a simple example that shows how the working set model helps reduce thrashing.

🎯 Goal: Build a step-by-step example that models a process's memory pages and how the working set model tracks pages to avoid thrashing.

📋 What You'll Learn

Create a list of page references representing memory accesses.

Define a window size to represent the working set time frame.

Use a loop to find the working set of pages in the current window.

Show the final working set for the last window of page references.

💡 Why This Matters

🌍 Real World

Operating systems use the working set model to decide which memory pages to keep in RAM and which to swap out, preventing thrashing and improving performance.

💼 Career

Understanding memory management concepts like thrashing and working sets is important for roles in system administration, software development, and performance optimization.

1

Create the list of page references

Create a list called page_references with these exact values: [1, 2, 3, 2, 4, 1, 5, 2, 1, 3, 4, 5].

Operating Systems

# Create the list of page references
# Your code here

Need a hint?

Think of page_references as the sequence of pages a program accesses in order.

2

Define the working set window size

Create a variable called window_size and set it to 4 to represent the number of recent page references to consider.

Operating Systems

page_references = [1, 2, 3, 2, 4, 1, 5, 2, 1, 3, 4, 5]
# Define the working set window size
# Your code here

Need a hint?

The window_size tells us how many recent pages to look at when finding the working set.

3

Find the working set for each window

Use a for loop with variable i to go from window_size to the length of page_references. Inside the loop, create a set called working_set containing the pages from page_references[i - window_size:i].

Operating Systems

page_references = [1, 2, 3, 2, 4, 1, 5, 2, 1, 3, 4, 5]
window_size = 4
# Use a for loop to find the working set for each window
# Your code here

Need a hint?

The loop moves a window over the page references. The working_set holds unique pages in that window.

4

Show the final working set

After the loop, create a variable called final_working_set and set it to the last working_set calculated.

Operating Systems

page_references = [1, 2, 3, 2, 4, 1, 5, 2, 1, 3, 4, 5]
window_size = 4
for i in range(window_size, len(page_references) + 1):
    working_set = set(page_references[i - window_size:i])
# Set final_working_set to the last working_set
# Your code here

Need a hint?

The final_working_set shows which pages are currently in use in the last window, helping to avoid thrashing.