this post was submitted on 13 Mar 2024
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Care to elaborate? Sounds promising
I’m not a hardware dev, but I’ve been following this issue for several months. Nvidia on Wayland does not implement implicit GPU synchronization currently for Xwayland. Other vendors do.
This issue is related to how/when the framebuffer from the gpu is handed off to be displayed. Implicit sync isn’t a great solution, it’s just what’s been done for Linux in the past.
Here’s a bit more detail if you’re interested:
I believe this issue is more specific to Wayland because Wayland relies on the DRM, direct rendering manager, to facilitate communication between the graphics driver and Wayland clients (applications). Whereas Xorg kinda just covered everything along the pipeline.
Implicit sync sounds like a bit of hack, where software (I assume the client? Or maybe the drm driver?) implicitly checks for the frame to be finished, rather than being signaled when the frame is ready.
So instead, Nvidia has been arguing for, designing and developing an explicit sync Wayland Protocol (and one for Xorg), which will let the graphics driver explicitly signal when a frame is finished and ready to be displayed. This is how the graphics stack works on Windows.
Right now on Nvidia, Xwayland clients will show previous frames, incomplete/corrupted frames or will fail to update when a new frame is rendered. Here’s the XWayland Merge Request. The issue is much worse on drivers > 535.xx after some optimizations worsened the issue. For now, rolling back can help!
There will be benefits in general with explicit sync, but the major ones will be Xwayland functioning properly for Nvidia users, VRR and apps with inconsistent framerates.
And apparently the plan is to have explicit sync ready for the next major driver version (v555).
From the discussions on Github and Gitlab it seems the work for that to happen is done. The changes in the necessary packages (Xwayland, Mesa?) just need to be merged and the the Nvidia driver 555 needs to be released. It hasn't been that long since the previous release 550. So I guess it is going to take a bit of waiting still.
Yeah, still gonna be a couple of months, but that is the last signifficant issue for me, fingers crossed.
It's the explicit sync protocol.
The TL;DR is basically: everyone else has supported implicit sync for ages, but Nvidia doesn't. So now everyone is designing an explicit sync Wayland protocol to accommodate for this issue.
It's explicit sync, look at my other comment for links