Memory Management Simulator

A complete simulation of an Operating System's Memory Management Unit (MMU), implemented in C++.
This project demonstrates Dynamic Memory Allocation, Multilevel Caching, and Virtual Memory Paging.

mem-sim.mp4

Features

1. Physical Memory Allocator

   • Strategies: First Fit, Best Fit, Worst Fit.
   • Buddy System: Recursive splitting and coalescing for power-of-2 blocks.
   • Coalescing: Automatic merging of adjacent free blocks.

2. Virtual Memory (Paging)

   • Translates Virtual Addresses to Physical Addresses.
   • Simulates Page Faults.
   • FIFO Page Replacement policy.
   • Configurable physical memory limits (frames).

3. Multilevel Cache

   • L1 Cache: 1KB, 2-way Set Associative.
   • L2 Cache: 4KB, 4-way Set Associative.
   • Hierarchy: CPU -> L1 -> L2 -> Main RAM.
   • Connects seamlessly with the Virtual Memory system (physically addressed cache).

Build Instructions

Prerequisites

• C++ Compiler (g++ or clang++) supporting C++17.
• Make (optional).

Building with Make

make

Manual Build

g++ -std=c++17 -I./include src/main.cpp src/MemoryManager.cpp src/cache/Cache.cpp src/virtual_memory/PageTable.cpp -o memsim

Usage

Run the simulator:

./memsim

1. Basic Allocation Mode

Simulate standard malloc/free behavior.

> init 1024              # Init 1024 bytes
> set allocator best_fit # Choose strategy
> malloc 200             # Alloc 200 bytes
> malloc 50
> free 1                 # Free block ID 1
> dump memory            # View heap map

2. Buddy System Mode

Simulate the Buddy Allocation algorithm.

> init 1024              # Must be power of 2
> set allocator buddy
> malloc 100             # Rounds to 128, splits blocks
> free 1

3. Virtual Memory & Cache Simulation

Simulate CPU memory access through the full hierarchy.

> vm init 256            # Init VM with 256 bytes of Physical RAM (4 Frames)
> access 0x0040          # Access Virtual Addr 0x40
                         # -> MMU Translates (Page Fault if needed)
                         # -> Physical Addr sent to Cache
                         # -> L1/L2 Hit/Miss logic
> vm stats               # Check Fault rates
> cache stats            # Check Hit rates

Project Structure

• src/: Source code.
• include/: Header files.
• tests/: Sample test scripts.
• docs/: Detailed design documentation.

Test Report Summary

Automated tests (tests/run_all_tests.bat) demonstrate the following system behaviors:

1. Allocation Strategies

• Fragmentation: Running test_scenario_1.txt with First Fit strategy resulted in 22.88% External Fragmentation with 0% Internal Fragmentation for the requested sizes.
• Cache Interaction: Memory accesses correctly triggered L1/L2 cache lookups, with initial cold misses filling the cache lines.

2. Buddy System

• Splitting: test_buddy.txt verified that a 100-byte request correctly splits a 1024-byte block down to a 128-byte block (Power of 2).
• Coalescing: Freeing adjacent buddies successfully triggered recursive merging, restoring the memory to a single 1024-byte free block.

3. Virtual Memory & Cache

• Page Faults: test_vm.txt demonstrated demand paging. Sequential accesses to distinct pages caused Page Faults and subsequent loading into frames.
• Address Translation: Virtual Address 0x100 was correctly translated to Physical Address 0xC0 (Frame 3