Project 12: POSIX Shared Memory Ring Buffer

A high-performance ring buffer in POSIX shared memory for producer-consumer communication between processes.

Quick Reference

Attribute Value
Primary Language C
Alternative Languages Rust
Difficulty Level 4 (Expert)
Time Estimate See main guide
Knowledge Area High-Performance IPC, Lock-Free
Tooling See main guide
Prerequisites See main guide

What You Will Build

A high-performance ring buffer in POSIX shared memory for producer-consumer communication between processes.

Why It Matters

This project builds core skills that appear repeatedly in real-world systems and tooling.

Core Challenges

  • Memory mapping → shm_open, ftruncate, mmap
  • Synchronization → Semaphores in shared memory
  • Cache coherency → Memory barriers and atomics

Key Concepts

  • Map the project to core concepts before you code.

Real-World Outcome

$ ./shm_ringbuffer_bench --buffer-size=1MB --iterations=10M

Shared Memory Ring Buffer Benchmark
Buffer: 1MB, Messages: 10 million

Producer: Writing 10M messages...
Consumer: Reading 10M messages...

Results:
  Throughput: 8.5 million msg/sec
  Bandwidth: 8.5 GB/sec
  Latency (avg): 0.12 μs
  Latency (p99): 0.35 μs
  Zero-copy: Yes

Comparison to pipe: 7x faster
Comparison to Unix socket: 6x faster

Implementation Guide

  1. Reproduce the simplest happy-path scenario.
  2. Build the smallest working version of the core feature.
  3. Add input validation and error handling.
  4. Add instrumentation/logging to confirm behavior.
  5. Refactor into clean modules with tests.

Milestones

  • Milestone 1: Minimal working program that runs end-to-end.
  • Milestone 2: Correct outputs for typical inputs.
  • Milestone 3: Robust handling of edge cases.
  • Milestone 4: Clean structure and documented usage.

Validation Checklist

  • Output matches the real-world outcome example
  • Handles invalid inputs safely
  • Provides clear errors and exit codes
  • Repeatable results across runs

References

  • Main guide: UNIX_IPC_STEVENS_VOL2_MASTERY.md
  • Primary references are listed in the main guide