X11 vs Wayland cursor latency
I don't think he should have included the starting frame-- if the cursor were theoretically instant, his method records it with a 1 frame delay, and this +1 frame error happens on every test. Correcting this actually makes Wayland more laggy proportionally, although it makes both less laggy absolutely.
What I've noticed with Wayland in Plasma is that it's very much tied to my monitors refresh rate.
At 240Hz, with adaptive sync turned off or to Automatic, I get a very responsive cursor.
At 75Hz, or if I force adaptive sync to be on at all times (instead of off or Automatic), then I get a noticeable mouse latency
I don't perceive this with Sway (1.10-2) using a mouse being polled at 1000 Hz.
When I turn on my monitor's FPS display and my mouse is not moving, the monitor reports that the frame rate drops down to the lowest rate available (48 Hz), then when the mouse is moving, jumps up to the highest rate.
investigates
Hmm. Apparently there's someone complaining about that behavior occurring in games during mouse movement, and saying that Sway's behavior is a bug.
https://github.com/swaywm/sway/issues/6832#issuecomment-1079941291
I guess the concern is that one doesn't want that to happen in a typical fullscreen game that can't render at the monitor's full frame rate, but do want to with, say, the desktop environment to keep the pointer responsive.
Honestly, while I use adaptive sync, I only really care about it for fullscreen movie playback, where I want the monitor to be able to run at the movie's framerate. I actually hadn't even thought about the fact that it affects games. Hmm.
Latency raw data :
instead of calculating the average one could decide to drop the data points that are way outside of their goups.
Doing so, in the first group I would neglect the value of Δ = 1 or 6 frame and in the second group I would neglect the value of 4 or 8 frames
Results :
X11 : from 3 to 5 frames
Wayland : from 5 to 6 frames
Δ(Δ) = 5.5 - 4 = 1.5
Still it doesn't change the final result that the difference between these two Gnome versions is 1.5 camera frames at 240 frames per second.
Good analysis
Thanks. Also, after a bit of thought, i do believe you are right saying that we should remove one frame of all the raw camera data. ... it will, as you say, decrease the absolute values and make Wayland more laggy proportionally, yet, it doesn't change the absolute difference.
I saw some cheap laptops with Ubuntu in a local mall and on them the latency on Wayland was unbearable.
I'd be very interested in sway and hyprlands numbers