Developer Explains Why Explicit Sync Will Finally Solve the NVIDIA/Wayland Issues

If you’ve ever wondered why some Linux users are experiencing issues with an NVIDIA GPU on Wayland and you aren’t, KDE developer Xaver Hugl explains in a recent post why the explicit sync protocol will finally settle the score for everyone.

You may have heard about explicit sync (short for explicit synchronization) being merged into the Wayland protocols recently. But what is it? Well, it’s a new protocol based on DRM synchronization objects where apps explicitly tell the userspace graphics driver, kernel, or compositor when rendering is complete.

Until now, when apps rendered things, they weren’t rendered immediately. This method is called “implicit sync” and involves apps recording a list of commands with the OpenGL or Vulkan drivers for the graphics card to execute, which could lead to the issues some of you are experiencing with NVIDIA and Wayland.

“This model makes it easy for application developers to write correctly working applications, but it can also cause issues,” said Xaver Hugl. “The most relevant of them for Wayland is that the application isn’t aware of which tasks it’s synchronizing to, and it can happen that you accidentally and unknowingly synchronize to GPU commands that don’t have any relevance to your task.”

With the explicit synchronization in place, these “accidental” synchronization will no longer happen. In addition, Xaver Hugl says that it will boost performance by reducing the work drivers have to do because apps will just tell them directly instead of having to figure out the dependencies of tasks from a list of commands.

“There’s been a lot of discussions around the Internet between people experiencing the issues constantly, and others not seeing any, and now you should know why it doesn’t seem to affect everyone,” explains Xaver Hugl. “This means that a lot of factors – like the apps you use, the CPU and GPU you have, the driver version, the kernel, compositor, and so on – decide whether or not you actually see the issue.”

So, long story short, the explicit sync protocol is something NVIDIA GPU users should look for this year as it is being implemented in Wayland compositors, the proprietary NVIDIA driver, and Xwayland to finally make everyone happy and encourage the Wayland adoption among NVIDIA users.

Image credits: NVIDIA Corporation (edited by Marius Nestor)

Last updated 1 week ago