Python 3.15's Ultra-Low Overhead Interpreter Profiling Mode Explained

Python 3.15's Ultra-Low Overhead Interpreter Profiling Mode – Ken Jin's Blog

I developed a new profiling mode for Python 3.15 that enables efficient trace recording for JIT compilation with minimal performance impact. By swapping dispatch tables instead of using dual interpreters or conditional branches, we achieved a mere 4.5x slowdown, significantly outperforming traditional tracing systems like PyPy. This approach offers a scalable path for low-overhead runtime analysis without complex rewrites.

"However, I do ask myself occasionally: is this magical system we've come up with in CPython worth the complexity?"