RadeonSI Patches Emerge For ARB_sparse_buffer
Written by Michael Larabel in Radeon on 8 February 2017 at 07:58 AM EST. 19 Comments
Nicolai Hähnle has been working on OpenGL ARB_sparse_buffer support within the RadeonSI Gallium3D driver stack along with the necessary core Mesa changes for this extension as well as some AMDGPU kernel changes.

ARB_sparse_buffer is described by the OpenGL Registry as "The ARB_sparse_texture extension adds to GL a mechanism to decouple the virtual and physical storage requirements of textures and allows an application to create partially populated textures that would over-subscribe available graphics memory if made fully resident. This extension provides like functionality for buffer objects, allowing applications to manage buffer object storage in a similar manner."

This work is going in the direction of supporting ARB_sparse_texture, which is like ARB_sparse_buffer but rather than being for generic buffers applies the same concepts to textures, and the extensions in turn building off that. The ARB_sparse_buffer extension was ARB'ed at the time of OpenGL 4.5 for allowing large buffer objects without the whole buffer being resident.

This is also related to the recent AMDGPU PRT patches for adding support for partially-resident textures (PRT) to the AMDGPU kernel driver. The PRT support wasn't queued up for Linux 4.11 and thus probably coming with Linux 4.12, which means the RadeonSI ARB_sparse_buffer support will be held up from mainline until that point.

The 21 patches for wiring up ARB_sparse_buffer in core Mesa and RadeonSI Gallium3D can be found on the Mesa mailing list.
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