tl;dr: Using a custom-built photodiode latency meter, the author measured end-to-end input latency across various Linux gaming configurations on a 500Hz display. Key findings: XWayland adds a significant 3.13ms penalty and should be avoided; X11 beats native Wayland by only 0.14-0.22ms; VRR provides the biggest gain (0.26-0.45ms) and flattens jitter; and dxvk-low-latency consistently improves latency, with its biggest wins in uncapped/GPU-bound scenarios (0.84ms). Stacking all optimizations only shaved 0.72ms off the median versus a default Wayland setup.