Process Scheduling Simulation

A multithreaded OS scheduler simulator written in C that models multiple CPUs and supports four scheduling algorithms. Built on top of the provided os‑sim framework, it safely manages concurrent CPU threads and a shared ready queue using POSIX threads, mutexes, and condition variables.

Repository:

git clone https://github.com/Minhong-Portfolio/Process-Scheduling-Simulation.git
cd Process-Scheduling-Simulation

Features

• FCFS (First‑Come, First‑Served)
• Round‑Robin with configurable timeslice (-r <ticks>)
• Preemptive Priority with Aging (-p <age_weight>)
• Shortest Remaining Time First (SRTF)
• Thread‑safe shared ready queue with pthread_mutex_t & pthread_cond_t
• Context switches via context_switch() and force_preempt() APIs
• Live Gantt chart output and final statistics for context switches and time-in-state

Prerequisites

• GCC (C99)
• Make
• POSIX‑compatible OS (Linux, macOS, WSL)

Building

# Build in optimized (release) mode
make

# For debugging symbols
make debug

# To run thread‑sanitizer checks
make tsan-debug

Usage

# FCFS on 4 CPUs
./os-sim 4

# Round‑Robin with a 5‑tick timeslice
./os-sim 4 -r 5

# Priority with aging weight 2
./os-sim 4 -p 2

# Shortest Remaining Time First
./os-sim 4 -s

Command‑Line Options

• <#CPUs> (1–16): number of simulated CPUs
• -r <timeslice>: Round‑Robin scheduling
• -p <age_weight>: Priority scheduling with aging
• -s: Shortest Remaining Time First
• -h: Display help and usage

Project Structure

├── src/                     # Source code and headers
│   ├── student.c            # Scheduling logic and handlers
│   ├── student.h            # Ready queue, scheduling APIs
│   ├── os-sim.h             # Simulator framework interface
│   ├── process.h            # PCB and op definitions
│   └── Makefile             # Build rules
├── examples/                # Example trace files (if any)
└── README.md                # This file

Example Output

Time  Ru Re Wa     CPU0     CPU1     CPU2     CPU3     < I/O Queue <
0.0   0  4  0      (IDLE)   (IDLE)   (IDLE)   (IDLE)   <            <
0.1   1  3  0      Iapache   Ibash    Imozilla  Ccpu    <            <
...

Total Context Switches: 42
Total Execution Time:  3.4 s
Time in READY state:   2.1 s

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Implemented by Minhong Cho (GTID: 903806863)