Virtual Memory Simulator

A virtual memory management simulation implemented in C. This project demonstrates paging, page faults, and page replacement algorithms.

Requirements

This project requires a Linux environment to compile and run. It relies on POSIX-specific headers and features (sys/mman.h, ucontext.h, signals) to simulate hardware page faults.

• Linux (Ubuntu, Fedora, etc.)
• WSL (Windows Subsystem for Linux) on Windows
• macOS (may require slight adjustments for ucontext definitions)

Note: This project will not compile with MinGW or Visual Studio on Windows directly.

Overview

This program simulates a virtual memory system mapping virtual pages to physical frames using a page table. It handles page faults by swapping pages in from an emulated disk.

It supports multiple page replacement policies:

• FIFO: First-In, First-Out.
• RAND: Random page replacement.
• CUSTOM: A custom prefetching algorithm that attempts to load the next sequential page.

Building the Project

To compile the project, run:

make

This generates the virtmem executable.

Running the Simulation

Usage:

./virtmem <npages> <nframes> <policy> <program>

• <npages>: Number of pages in the virtual address space.
• <nframes>: Number of physical frames available.
• <policy>: Replacement policy (fifo, rand, or custom).
• <program>: The test program to run (alpha, beta, gamma, delta).

Arguments Detail

• npages: Must be >= 1.
• nframes: Must be >= 1.
• policy:
  • fifo: Evicts the oldest page.
  • rand: Evicts a random page.
  • custom: Uses a predictive prefetching strategy.
• program:
  • alpha: Linear scan access pattern.
  • beta: Random access pattern.
  • gamma / delta: Other specific access patterns to test algorithm performance.

Examples

Run with 100 pages, 10 frames, FIFO policy, executing the 'scan' program (alpha):

./virtmem 100 10 fifo alpha

Run with 50 pages, 5 frames, Random policy, executing the 'sort' program (beta):

./virtmem 50 5 rand beta

Output

The program will simulate memory accesses and output the final statistics:

• Page Faults: Number of times a page had to be fetched from disk.
• Disk Reads: Number of blocks read from the swap disk.
• Disk Writes: Number of blocks written to the swap disk (evicted dirty pages).

Summary: Page Faults - 120 | Disk Reads - 120 | Disk Writes - 45