Measuring Input Latency on Linux: X11 vs. Wayland, VRR, and DXVK

A Linux gamer built a custom hardware device to measure input latency by using a light sensor attached to a monitor that detects screen changes triggered by simulated mouse clicks, allowing precise end-to-end system latency measurements. The device combines a microcontroller, photodiode, and USB interface to collect 12,000 samples per click and calculate the exact time between input and visual response, providing reliable data to verify whether various Linux gaming optimizations (like Wayland vs. X11, VRR, or DXVK forks) actually reduce latency or are placebo effects.