OpenGL has the concept of streaming buffers these buffers are marked to be
rewritten and used a small number of times. Vulkan (being low-level API)
doesn't have this concept. When performing font rendering Blender uses
streaming buffers and can slow down Vulkan as GPU barriers are added
between uploading and using the buffer.
Using a different approach could reduce the GPU barriers. The overall
idea is:
Altering render graph nodes
During font rendering the streaming buffer is rewritten from start with
the data to render the next part. This could only cover a part of the fully
allocated buffer. And would introduce a barrier before and after rewritting
the next part.
The allocated buffer on the GPU can fit more data but that data needs to be
passed along the first update to reduce the barriers. Allowing access to an
existing node in the render graph would allow to change the initial upload to
upload more data, without additional barriers.
VKStreamingBuffer
A new buffer type is introduced that will keep track of the streaming buffer
on the current render graph. A streaming buffer can be shared between multiple
threads and requires state manager to be done per context.
Pull Request: https://projects.blender.org/blender/blender/pulls/146956
cfeacef394