Unstable frametime with VSync enabled

I have a 75 Hz refresh rate monitor. With VSYNC enabled, I should have had a stable 13 ms frame time, like in vanilla. Instead, I'm getting a repeating pattern of one very fast frame, two 13 ms frames, and one ~26 ms frame.

Here's a screenshot with the bug:

Here's vanilla for the comparison:

Steps to reproduce

1. Change render distance and simulation settings to the minimum
2. Enable VSync
3. Disable FPS limit
4. Create a superflat world
5. Look straight down
6. You get unstable frametimes

Log files

2024-11-20-2.log

Seems like it's reproducible only on X11. On wayland (with patched glfw) it's fine.

This is a very old Nvidia-specific bug that effects all VulkanMod versions, driver versions and platforms, including Windows
(My GTX 1080 Ti has broken VSync on both Windows and X11 as well)

Wayland, Nvidia Optimus devices, and windowed mode on Windows are the only exceptions to my knowledge
As iirc they prevent screen tearing, which seems to suppress the stutter (When VSync is Enabled)
(i.e. like the in-game FPS Limiter)

ATM i'm currently working with Collateral on a experimental fix for this

If the fix works and doesn't cause any problems/bugs of its own, it should hopefully be included in either 0.5.2 or a later VulkanMod version at some point

Wayland, Nvidia Optimus devices, and windowed mode on Windows are the only exceptions to my knowledge
As iirc they prevent screen tearing, which seems to suppress the stutter
(i.e. like the in-game FPS Limiter)

Actually, Wayland doesn't limit the framerate if I disable VSync.