Chapter 48: Performance Tuning in Kotlin

io_uring, SIMD JSON, buffer pooling. In this chapter, you will learn performance tuning in depth with Kotlin code examples, explanations, and best practices.

Overview

This chapter covers performance tuning for Kungfu.js developers using Kotlin. We will start with the basics, move through practical examples, and end with advanced techniques and common pitfalls.

Why This Matters

Understanding performance tuning is essential because it is a core part of building web applications. Every real-world app needs to handle io_uring, simd json, buffer pooling. Skipping this chapter would leave a gap in your knowledge that would cause problems later.

Code Example

Here is how to handle this in Kotlin:

# Build with maximum performance
cargo build --release --features "kungfu-core/io_uring kungfu-core/simd"

# Production settings
# - Set acceptor_threads to CPU core count
# - Enable io_uring (Linux 5.1+)
# - Enable SIMD JSON (x86_64 with AVX2)
# - Use buffer pooling
# - Enable TCP_NODELAY
# - Increase file descriptors: ulimit -n 1048576

Performance Features

  • io_uring: Zero-copy I/O on Linux 5.1+. Reduces syscalls by 10-20x.
  • SIMD JSON: Uses CPU vector instructions for JSON parsing. 2-4x faster on x86_64.
  • Buffer pooling: Reuses memory buffers instead of allocating new ones per request.
  • SO_REUSEPORT: Multiple acceptor threads share the same port. Kernel load-balances connections.
  • TCP_NODELAY: Disables Nagle's algorithm for lower latency on small responses.

Common Mistakes

  • Not reading the documentation: Always check the API reference when something does not work as expected.
  • Skipping security: Never disable the default middleware unless you have a very good reason. Security is not optional.
  • Not testing: Write tests for your handlers. Kungfu.js makes this easy with the built-in test utilities.

Summary

In this chapter, you learned about performance tuning in Kotlin. You saw code examples, understood how things work under the hood, and learned about common mistakes to avoid.

What is Next?

In chapter 49, we will cover Deployment: Docker, systemd, Vercel, production checklist.

Previous: Testing Your AppNext: Deployment