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

14 days ago

The author switched to Linux for gaming to achieve better FPS, frame pacing, and input latency, but lacked reliable measurement tools.
To measure end-to-end system latency, the author built a device with a light sensor that detects screen changes after a simulated mouse click, inspired by open-source projects like OSLTT.
The author tested three aspects: X11 vs Wayland input lag, Variable Refresh Rate (VRR) benefits, and the low-latency fork of DXVK (dxvk-low-latency).
Results showed X11 had slightly lower latency than Wayland (0.14-0.22 ms difference), contrary to perceptions of Wayland being much worse.
VRR consistently reduced latency (0.26-0.45 ms) and flattened latency distribution by allowing frames to scan out when ready.
dxvk-low-latency provided small gains in capped scenarios (0.10-0.29 ms) but significantly smoothed frame pacing and reduced latency in uncapped tests (0.84 ms gain).
XWayland added substantial latency (3.13 ms without dxvk-low-latency), but dxvk-low-latency mitigated this by 2.11 ms.
Overall optimizations (X11, VRR, dxvk-low-latency) reduced median latency by 0.72 ms compared to default Wayland, with additional benefits in reducing jitter and handling real-world fluctuations.
Other sources like David Ramiro and farnoy corroborated findings, noting native Wayland matches X11 latency while XWayland should be avoided.
The author's setup used specific hardware (AMD Ryzen 7 5800X3D, NVIDIA RTX 4070 SUPER) and software (CachyOS, KDE Plasma), with results likely transferring to other setups, especially on lower refresh rate displays.

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