XINU Operating System Projects (CSC 501)

This repository contains a collection of operating system projects implemented in the XINU OS as part of CSC 501. The projects focus on core OS concepts including process scheduling, synchronization, and virtual memory management.

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📁 Project Structure

xinu-projects/
│── PA1/   # Process Scheduling
│── PA2/   # Readers-Writer Locks & Priority Inheritance
│── PA3/   # Demand Paging & Virtual Memory

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🚀 Overview

🔹 PA1: Process Scheduling

Implemented custom scheduling algorithms to improve fairness and prevent starvation:

• Aging-based scheduler with dynamic priority adjustments
• Linux-like scheduler using epochs, time quanta, and goodness metrics
• Runtime switching between scheduling policies

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🔹 PA2: Synchronization (Readers-Writer Locks)

Extended kernel synchronization primitives:

• Implemented readers-writer locks supporting concurrent reads
• Designed priority-based lock scheduling policies
• Developed priority inheritance to handle priority inversion
• Ensured fairness and correctness under concurrent workloads

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🔹 PA3: Demand Paging & Virtual Memory

Built a virtual memory system with demand paging:

• Implemented memory mapping (xmmap, xmunmap)
• Designed per-process virtual heaps (vcreate, vgetmem, vfreemem)
• Developed backing store management and inverted page tables
• Implemented page fault handling (ISR 14)
• Added page replacement policies (Second-Chance & FIFO)

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🛠️ Technologies & Concepts

• C Programming
• XINU Operating System
• Process Scheduling Algorithms
• Synchronization & Concurrency
• Virtual Memory & Paging
• Page Replacement Algorithms
• Kernel-Level Development

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📊 Key Learnings

• Deep understanding of OS internals and kernel design
• Hands-on experience with scheduling, memory management, and synchronization
• Debugging low-level systems code and handling edge cases
• Designing efficient and fair resource management strategies

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▶️ How to Run

1. Set up the XINU environment (based on course instructions)

2. Navigate to the desired project folder:

   cd PA1   # or PA2 / PA3
   

3. Build and run:

   make clean
   make
   

4. Use provided test files (e.g., testmain.c) to validate functionality

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📌 Notes

• Each project builds upon core XINU kernel functionality
• Code modifications are primarily in kernel source files (system/, paging/, etc.)
• Designed and tested on an emulated XINU environment

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