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LuaJIT Performance Optimization

1 post · Feb 2017 – Dec 2018

What this trail covers

Cloudflare has been involved in optimizing LuaJIT performance through a research project at King's College London. This project focused on developing a comprehensive benchmark suite for Lua implementations, analyzing the performance of different LuaJIT forks (original LuaJIT and RaptorJIT), and identifying areas for optimization. The work has led to a better understanding of VM warmup behavior and performance characteristics across various benchmarks.

All Cloudflare trails
  1. More consistent LuaJIT performanceThis post details the creation of a larger, more comprehensive benchmark suite for Lua implementations, a simple benchmark runner (simplerunner.lua), and a comparison of the original LuaJIT repository with RaptorJIT. It presents detailed benchmark results and introduces a stats differ tool for comparing benchmark sets.
  2. LuaJIT Hacking: Getting next() out of the NYI listThis post introduces 'loom', a custom HTML-formatted tool for visualizing LuaJIT's JIT compilation traces, offering more detail and cross-references than the standard `-jdump` option. It also details the problem of `next()` and `pairs()` being 'Not Yet Implemented' (NYI) in LuaJIT, forcing code to run in the interpreter and incurring significant performance penalties, especially when using the FFI library. The post outlines the steps taken to get `next()` out of the NYI list, enabling it to be JIT-compiled.