Embedded Files
Modern computing requires more memory than what is physically available in RAM. When RAM reaches capacity, the system uses virtual memory as a temporary extension. Understanding how virtual memory works helps explain how computers manage performance and multitasking. Virtual memory is not related to cloud computing.
Learning Objectives
Learning Objectives
By the end of this lesson, I can:
Explain the purpose of virtual memory.
Understand how virtual memory supports system performance.
Key Terms
Key Terms
Virtual Memory - A section of the hard drive used as an extension of RAM.
Page File - A reserved space on the disk where memory pages are stored temporarily.
Swapping - The process of moving data between RAM and virtual memory.
Thrashing - When excessive swapping slows down system performance.
Paging - Dividing memory into fixed-size blocks for management.
Disk Latency - The delay in accessing data stored on a hard drive compared to RAM.
Segmentation - Dividing memory into different-sized sections for efficient allocation.
Memory Management Unit (MMU) - A hardware component that handles virtual memory operations.
Virtual Memory explained..
Virtual Memory explained..
Virtual memory is a section of a computer’s storage drive (HDD/SSD) that acts as temporary RAM when the actual RAM is full. The operating system (OS) manages virtual memory automatically by moving least-used data from RAM to a page file on the storage drive. This process, called swapping, allows more applications to run at once but slows performance because storage drives are much slower than RAM.
When a program needs data stored in virtual memory, the OS must swap it back into RAM, causing a page fault. If this happens too often, the computer can experience thrashing, where it spends more time swapping data than running programs, making the system very slow. Thrashing is a common issue on computers with low RAM or slow HDDs. SSDs improve virtual memory performance but can wear out faster due to frequent read/write operations.
To organize memory efficiently, the OS uses paging and segmentation. Paging divides memory into fixed-sized blocks (pages), making allocation easier but sometimes leading to wasted space. Segmentation divides memory into variable-sized sections, which reduces waste but is harder to manage. The Memory Management Unit (MMU) keeps track of which parts of a program are in RAM and which are in virtual memory, ensuring smooth operation.
Although virtual memory helps prevent crashes, increasing RAM is the best solution for better performance. Users can adjust virtual memory settings, including changing the page file size or moving it to a different drive to improve efficiency. However, embedded systems do not use virtual memory because they are designed to run with a fixed amount of RAM and optimized software.
Virtual memory should not be confused with cache memory, which is a small, high-speed memory built into the CPU to store frequently used instructions. While cache memory speeds up processing, virtual memory prevents the system from running out of memory.
Key Ideas
Key Ideas
Virtual memory is a section of a computer’s storage drive (HDD/SSD) used as temporary RAM when RAM is full.
Automatic Management: The operating system (OS) manages virtual memory automatically by moving least-used data from RAM to a page file on the storage drive (swapping).
Performance Impact: Virtual memory slows performance because storage drives are much slower than RAM.
Page Faults & Thrashing:
When a program needs data from virtual memory, the OS swaps it back into RAM, causing a page fault.
If this happens too often, the system experiences thrashing, where it spends more time swapping data than running programs, making it very slow.
Low RAM and slow HDDs are more likely to suffer from thrashing.
SSDs improve performance but can wear out faster due to frequent read/write operations.
Memory Management Techniques:
Paging: Divides memory into fixed-sized blocks (pages), making allocation easier but sometimes wasting space.
Segmentation: Divides memory into variable-sized sections, reducing waste but making management more complex.
The Memory Management Unit (MMU) tracks which parts of a program are in RAM and which are in virtual memory.
Optimizing Virtual Memory:
Increasing RAM is the best way to improve performance.
Users can adjust virtual memory settings, such as changing the page file size or moving it to a different drive.
Embedded Systems: Do not use virtual memory, as they are designed to work efficiently with fixed RAM and optimized software.
Difference from Cache Memory:
Cache memory is a small, high-speed memory built into the CPU for storing frequently used instructions, improving processing speed.
Virtual memory prevents system crashes by providing extra space when RAM is full, but it does not speed up processing.
Tips & Mistakes to Avoid
Tips & Mistakes to Avoid
✅ Virtual memory helps prevent system crashes when RAM is full.
✅ Paging and segmentation help efficiently allocate memory to different processes.
🚫 Mistake: Thinking virtual memory makes a computer faster—it's much slower than RAM.
🚫 Mistake: Ignoring thrashing—excessive swapping can slow a computer significantly.
Video: Virtual Memory
Video: Virtual Memory
Summary: Explains how virtual memory extends RAM and the impact on system performance.
Remember to pause the video to make notes in your workbook whenever you see this icon.
Case Study: Windows Page File
Case Study: Windows Page File
Most modern operating systems, including Windows, MacOS, and Linux, use a page file (also called a swap file) to manage virtual memory. Windows dynamically allocates virtual memory based on system demand, storing inactive program data on the hard drive. This helps prevent crashes when RAM is full.
However, excessive reliance on the page file leads to thrashing, where the system spends more time swapping data between RAM and virtual memory than actually running applications. This dramatically slows down performance.
To optimize performance, users can manually adjust virtual memory settings in Windows by setting a fixed page file size or letting the system manage it automatically. On Linux, a separate swap partition is used instead of a page file. MacOS also uses a swap file, but Apple optimizes memory management differently to reduce thrashing. Understanding these differences helps users make better decisions when configuring memory for performance.
RED TASKS
RED TASKS
Getting Ready..
Getting Ready..
Add a new slide called L2 - Virtual Memory
Choose an image/icon that represents memory management.
Copy the Comprehension Questions and Research Task into your slide.
Complete the Comprehension Questions after reading this page - do not use external research to help you complete them.
Complete the Research Task using external sources but do NOT use AI.
Add more slides whenever neccessary.
Comprehension Questions
Comprehension Questions
What is virtual memory, and why is it needed?
How does the operating system manage virtual memory automatically?
What is swapping, and how does it affect computer performance?
What is a page fault, and when does it occur?
What is thrashing, and why does it slow down a computer?
How do SSDs improve virtual memory performance, and what is their disadvantage?
What is the difference between paging and segmentation?
What role does the Memory Management Unit (MMU) play in virtual memory?
How can users optimize virtual memory settings to improve efficiency?
What is the difference between virtual memory and cache memory?
Research Task
Research Task
Research how virtual memory is managed on MacOS or Linux and compare it to Windows.
Create a table with a column for each OS and rows to to compare your findings.
Exam-Style Questions
Exam-Style Questions
Explain why computers need virtual memory. (4 marks)
Discuss how excessive reliance on virtual memory affects system performance. (6 marks)
Describe the process of swapping and explain its impact on computer performance. (4 marks)
Explain the difference between paging and segmentation in memory management. (5 marks)
Evaluate the advantages and disadvantages of using SSDs for virtual memory. (6 marks)
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