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KhronosGroup / MoltenVK

MoltenVK is a Vulkan Portability implementation. It layers a subset of the high-performance, industry-standard Vulkan graphics and compute API over Apple's Metal graphics framework, enabling Vulkan applications to run on macOS, iOS and tvOS.
Apache License 2.0
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Issues with presentation on certain AMD GPUs #1554

Open FleetAdmiralButter opened 2 years ago

FleetAdmiralButter commented 2 years ago

Hi,

We've been seeing an issue with certain AMD GPUs where the Final Fantasy XIV game will be running at a high frame rate (70FPS+) with smooth frame times, but the actual presentation of the game to the screen seems to be occurring at a low refresh rate. This results in movements/animations that seem incredibly choppy, regardless of the game's frame rate.

This issue is present on MoltenVK version 1.1.1 onward and occurs regardless of whether the game is running in Borderless Fullscreen, or Exclusive Fullscreen. The issue does not occur when running Windowed.

At first I thought the issue only affected the AMD 5xx family. However, I tested this with an AMD Radeon 6600XT and ran into the same stuttering. Additional testing showed that higher end GPUs of the same family, such as the Radeon 6900XT, were not affected. M1 GPUs don't seem to be affected by this either.

Here's a screenshot showing the FPS/frame time: image

Playing with the frame rate settings in-game do seem to alleviate this somewhat. Setting the game to a 30FPS cap (Refresh Rate 1/2) stops the stuttering even though the game doesn't even get limited to 30FPS and continues running at 70FPS+.

Compiling MoltenVK with kMVKMinSwapchainImageCount set to 3 does improve things slightly, but the issue is still very noticeable.

I'm quite certain that this to some problem happening with presentation, as my monitor reports that it is receiving a signal below 48Hz (the lowest the VRR can go). Working around the issue by setting the frame rate cap as described above results in the monitor reporting that it is receiving a signal with a refresh rate matching the FPS the game is running at.

This is a list of the GPUs that we've found to have exhibited this issue so far:

zebe commented 2 years ago

I believe this is the issue I was seeing on my iMac with Radeon Pro 580.

FleetAdmiralButter commented 2 years ago

Just a small update - have managed to reproduce this same issue in Nier Automata as well.

In both FFXIV and NieR, this issue can be worked around by forcefully disabling Vsync in DXVK:

dxgi.syncInterval = 0
dxgi.numBackBuffers = 3
dxgi.maxFrameLatency = 1
billhollings commented 2 years ago

This issue is present on MoltenVK version 1.1.1 onward

Does this imply that you did not find the same issue on versions of MoltenVK before that? If so, is it possible to bisect to the MoltenVK commit that caused the change?