In Vulkan multiple commands can be in flight simultaneously.
These commands can share resources like descriptor sets or push
constants. When between commands these resources are updated
a new version of the resources should be created.
When a resource is updated it should check the submission id of the
command buffer. If this is different than last known by the resources,
the previous resources should be freed.
If the submission id is the same than previously it has to create a
new version of the resource to not intervene with other commands that
uses the resource before the update.
When the resource wasn't updated between multiple usages in the same
submission id it could reuse the previous resource.
This PR introduces a `ResourceTracker` and a `SubmissionTracker`.
A submission tracker can check if the command buffer is submitted.
In this case all resources of the resource tracker should be freed.
Unmodified resources in the same submission can be shared.
A resource tracker will keep track of all resources that are in
flight. After the resources are used (submission + execution) have
finished the resources can be cleared.
Pull Request: blender/blender#105183
**What are push constants?**
Push constants is a way to quickly provide a small amount of uniform data to shaders.
It should be much quicker than UBOs but a huge limitation is the size of data - spec
requires 128 bytes to be available for a push constant range.
**What are the challenges with push constants?**
The challenge with push constants is that the limited available size. According to
the Vulkan spec each platform should at least have 128 bytes reserved for push
constants. Current Mesa/AMD drivers supports 256 bytes, but Mesa/Intel is only 128
bytes.
**What is our solution?**
Some shaders of Blender uses more than these boundaries. When more data is needed
push constants will not be used, but the shader will be patched to use an uniform
buffer instead. This mechanism will be part of the Vulkan backend and shader
developers should not see any difference on API level.
**Known limitations**
Current state of the vulkan backend does not track resources that are in the
command queue. This patch includes some test cases that identified this issue as
well. See #104771.
Pull Request #104880
This patch adds initial support for compute shaders to
the vulkan backend. As the development is oriented to the test-
cases we have the implementation is limited to what is used there.
It has been validated that with this patch that the following test
cases are running as expected
- `GPUVulkanTest.gpu_shader_compute_vbo`
- `GPUVulkanTest.gpu_shader_compute_ibo`
- `GPUVulkanTest.gpu_shader_compute_ssbo`
- `GPUVulkanTest.gpu_storage_buffer_create_update_read`
- `GPUVulkanTest.gpu_shader_compute_2d`
This patch includes:
- Allocating VkBuffer on device.
- Uploading data from CPU to VkBuffer.
- Binding VkBuffer as SSBO to a compute shader.
- Execute compute shader and altering VkBuffer.
- Download the VkBuffer to CPU ram.
- Validate that it worked.
- Use device only vertex buffer as SSBO
- Use device only index buffer as SSBO
- Use device only image buffers
GHOST API has been changed as the original design was created before
we even had support for compute shaders in blender. The function
`GHOST_getVulkanBackbuffer` has been separated to retrieve the command
buffer without a backbuffer (`GHOST_getVulkanCommandBuffer`). In order
to do correct command buffer processing we needed access to the queue
owned by GHOST. This is returned as part of the `GHOST_getVulkanHandles`
function.
Open topics (not considered part of this patch)
- Memory barriers & command buffer encoding
- Indirect compute dispatching
- Rest of the test cases
- Data conversions when requested data format is different than on device.
- GPUVulkanTest.gpu_shader_compute_1d is supported on AMD devices.
NVIDIA doesn't seem to support 1d textures.
Pull-request: #104518
