VK3D-Proton Update Brings In Enhanced OpenXR/OpenVR Support Along With Revamped “Proton ReBar”

VK3D-Proton, the famous compatibility layer, has received a new update, which enhances OpenXR/OpenVR support and includes several other changes.

VK3D-Proton’s Latest Update Targets Taking Linux Gaming Experience To New Levels, Brings In Crucial Changes

The new version, 2.13, primarily includes multiple adjustments to improve the gaming experience on Linux. For those unaware, the VK3D-Proton is a compatibility layer specifically for DX12 within the Proton environment, allowing Windows games to function seamlessly in the Linux ecosystem without third-party modification. With the latest update, the team has brought in several interesting changes, including implementing Shader Model 6.8 along with interoperability for OpenVR/OpenXR on Proton. Here are the features of the new update:

  • Implement Shader Model 6.8 min-spec
    • SV_StartInstanceLocation
    • SV_StartVertexLocation
    • WaveSize range
    • Implement Vulkan texturing catch-up features (esoteric comparison sampling functions)
  • Implement interop for OpenVR / OpenXR on Proton
  • Correctly support NULL index buffers with VK_KHR_maintenance6.
  • Implement VK_MESA_image_alignment_control. Reduces memory bloat on AMD cards in particular.

Apart from that, Valve’s Proton developers have introduced another interesting performance change: the adjustments made to the Proton ReBar or Proton Resizable BAR. This bar is designed to allow the CPU unrestricted GPU access to its allocated memory region, improving efficiency and performance. With the new change, however, GPUs with higher than 8 GB VRAM will only be able to access the feature since the developers say that lower memory GPUs had a “risk of more important memory being demoted to system memory.”

Following are all the performance enhancements within the new update (via GitHub):

  • Tweak how we opt-in to ReBAR for UPLOAD heaps. Now, only > 8 GB cards will get it.
    On 8 GB cards, we were regularly hitting the upper limits of what the GPU could hold in VRAM,
    and using ReBAR would be detrimental to performance since there was risk of more important
    memory being demoted to system memory. Works well together with VK_MESA_image_alignment_control
    to free up significant amounts of VRAM. Performance gains from ReBAR on 8 GB were also found to be minimal
    compared to the larger GPUs since we quickly exhausted the limited 512 MiB budget anyway.
  • Sub-allocate small image heaps. Avoids heavy stutter in Ghost of Tsushima on desktop.
    (Steam Deck code path does not seem to use small heaps to begin with).
  • Improve performance with ROV when used with more complicated shader code patterns.

The new update also improves the experience of NVIDIA’s Reflex technology but on the latest drivers. Overall, the new version 2.13 is solid and will improve the gaming experience on Linux, especially for high-end consumers.

News Source: Phoronix

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