Zink¶
Overview¶
The Zink driver is a Gallium driver that emits Vulkan API calls instead of targeting a specific GPU architecture. This can be used to get full desktop OpenGL support on devices that only support Vulkan.
Features¶
The feature-level of Zink depends on two things; what’s implemented in Zink, as well as the capabilities of the Vulkan driver.
The feature-levels implemented by Zink are exposed by Vulkan Profiles in the
VP_ZINK_requirements.json
profiles file.
Used with the Vulkan Profiles tools, we can compare the ZINK profiles with Vulkan devices profiles generated with Vulkaninfo or downloaded from GPUinfo.org to establish the feature-levels supported by these drivers.
OpenGL 2.1¶
OpenGL 2.1 is the minimum version Zink can support, and will always be exposed, given Vulkan support. There’s a few features that are required for correct behavior, but not all of these are validated; instead you’ll see rendering-issues and likely validation error, or even crashes.
Here’s a list of those requirements:
Vulkan 1.0
VkPhysicalDeviceFeatures
:Device extensions:
VK_EXT_custom_border_color with
customBorderColorWithoutFormat
VK_EXT_line_rasterization, with the following
VkPhysicalDeviceLineRasterizationFeaturesEXT
:
In addition to this, VK_KHR_external_memory is required to support the DRI code-path.
We also require either the VK_EXT_scalar_block_layout extension or Vulkan 1.2, with the scalarBlockLayout feature.
OpenGL 3.0¶
For OpenGL 3.0 support, the following additional requirements must be met:
VkPhysicalDeviceFeatures
:Device extensions:
OpenGL 3.1¶
For OpenGL 3.1 support, the following additional VkPhysicalDeviceLimits
are required:
maxPerStageDescriptorSamplers
≥ 16
OpenGL 3.2¶
For OpenGL 3.2 support, the following additional requirements must be met, although some of these might not actually get verified:
VkPhysicalDeviceFeatures
:Device extensions:
OpenGL 3.3¶
For OpenGL 3.3 support, the following additional requirements must be met, although some of these might not actually get verified:
VkPhysicalDeviceFeatures
:Device extensions:
OpenGL 4.0¶
For OpenGL 4.0 support, the following additional requirements must be met:
VkPhysicalDeviceFeatures
:Device extensions:
Formats requiring
VK_FORMAT_FEATURE_UNIFORM_TEXEL_BUFFER_BIT
:VK_FORMAT_R32G32B32_SFLOAT
VK_FORMAT_R32G32B32_SINT
VK_FORMAT_R32G32B32_UINT
OpenGL 4.1¶
For OpenGL 4.1 support, the following additional requirements must be met:
VkPhysicalDeviceFeatures
:VkPhysicalDeviceLimits
maxImageDimension1D
≥ 16384maxImageDimension2D
≥ 16384maxImageDimension3D
≥ 2048maxImageDimensionCube
≥ 16384maxImageArrayLayers
≥ 2048maxViewports
≥ 16
OpenGL 4.2¶
For OpenGL 4.2 support, the following additional requirements must be met:
- Device extensions:
VkPhysicalDeviceLimits
:shaderStorageImageExtendedFormats
shaderStorageImageWriteWithoutFormat
vertexPipelineStoresAndAtomics
fragmentStoresAndAtomics
For Vulkan 1.2 and above:
VkPhysicalDeviceVulkan11Features
:
For Vulkan 1.1 and below:
Device extensions:
OpenGL 4.3¶
For OpenGL 4.3 support, the following additional requirements must be met:
VkPhysicalDeviceFeatures
:Formats requiring
VK_FORMAT_FEATURE_SAMPLED_IMAGE_BIT
:VK_FORMAT_R8G8B8A8_UNORM
VK_FORMAT_R8G8B8A8_SRGB
VK_FORMAT_R16_UNORM
VK_FORMAT_R16G16_UNORM
VK_FORMAT_R16_SNORM
VK_FORMAT_R16G16_SNORM
VK_FORMAT_D32_SFLOAT_S8_UINT
OpenGL 4.4¶
For OpenGL 4.4 support, the following additional requirements must be met:
Formats requiring
VK_FORMAT_FEATURE_VERTEX_BUFFER_BIT
:VK_FORMAT_B10G11R11_UFLOAT_PACK32
For Vulkan 1.2 and above:
VkPhysicalDeviceVulkan12Features
:samplerMirrorClampToEdge
For Vulkan 1.1 and below:
Device extensions:
OpenGL 4.5¶
For OpenGL 4.5 support, the following additional VkPhysicalDeviceFeatures
are required to be supported
OpenGL 4.6¶
For OpenGL 4.6 support, the following additional requirements must be met:
VkPhysicalDeviceFeatures
:Device extensions:
Performance¶
If you notice poor performance and high CPU usage while running an application, changing the descriptor manager may improve performance:
- ZINK_DESCRIPTORS <mode> ("auto")¶
auto
Automatically detect best mode. This is the default.
lazy
Attempt to use the least amount of CPU by binding descriptors opportunistically.
db
Use EXT_descriptor_buffer when possible.
Debugging¶
There’s a few tools that are useful for debugging Zink, like this environment variable:
- ZINK_DEBUG¶
Accepts the following comma-separated list of flags:
nir
Print the NIR form of all shaders to stderr.
spirv
Write the binary SPIR-V form of all compiled shaders to a file in the current directory, and print a message with the filename to stderr.
tgsi
Print the TGSI form of TGSI shaders to stderr.
validation
Dump Validation layer output.
sync
Emit full synchronization barriers before every draw and dispatch.
compact
Use a maximum of 4 descriptor sets
noreorder
Do not reorder or optimize GL command streams
gpl
Force using Graphics Pipeline Library for all shaders
rp
Enable render pass optimizations (for tiling GPUs)
norp
Disable render pass optimizations (for tiling GPUs)
map
Print info about mapped VRAM
flushsync
Force synchronous flushes/presents
noshobj
Disable EXT_shader_object
optimal_keys
Debug/use optimal_keys
noopt
Disable async optimized pipeline compiles
nobgc
Disable all async pipeline compiles
mem
Enable memory allocation debugging
quiet
Suppress probably-harmless warnings
Vulkan Validation Layers¶
Another useful tool for debugging is the Vulkan Validation Layers.
The validation layers effectively insert extra checking between Zink and the
Vulkan driver, pointing out incorrect usage of the Vulkan API. The layers can
be enabled by setting the environment variable VK_LOADER_LAYERS_ENABLE
to
VK_LAYER_KHRONOS_validation
. You can read more about the Validation Layers
in the link above.
Apple macOS and MoltenVK¶
Zink on macOS is experimental with very limited capabilities.
The Vulkan SDK (1.3.250 or newer) is required to build Zink.
Set the build option -Dmoltenvk-dir=<directory>
to point at your Vulkan SDK install or MoltenVK build.
Add Zink to the Gallium drivers build option -Dgallium-drivers=zink
.
If installed using brew
, you can set -D moltenvk-dir=$(brew --prefix molten-vk)
.
IRC¶
In order to make things a bit easier to follow, we have decided to create our own IRC channel. If you’re interested in contributing, or have any technical questions, don’t hesitate to visit #zink on OFTC and say hi!