測量 Linux 上的輸入延遲：X11 vs Wayland、VRR 與 DXVK Low-Latency
Measuring Input Latency on Linux: X11 vs Wayland, VRR, and DXVK Low‑Latency
TL;DR – What the numbers mean
- X11 vs. Wayland: X11 is marginally faster (0.14–0.22 ms), not enough to explain the common perception that Wayland feels slower.
- Variable Refresh Rate (VRR): Enabling VRR consistently reduces latency by 0.26–0.45 ms and tightens the latency distribution.
- DXVK low‑latency fork: In capped scenarios it trims 0.10–0.29 ms; in uncapped, GPU‑bound runs it cuts 0.84 ms and smooths frame‑time spikes.
- XWayland: Adds a huge 3.13 ms penalty, dwarfing all other effects.
- Overall gain: Applying every optimization (X11 + VRR + DXVK low‑latency) lowers median end‑to‑end latency by ~0.72 ms compared to a default plain Wayland setup.
How the measurement works
The author built a click‑to‑photon rig a using an Adafruit QT Py RP2040 that:
- Sends a USB HID mouse click at a 1000 Hz poll rate.
- Immediately starts sampling a photodiode mounted on the monitor (≈24 µs per sample, 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