RadeonSI Lands SDMA Copy Support For Vega/GFX9
The RadeonSI Gallium3D driver has finally landed SDMA copy support for Vega/GFX9 graphics hardware, which should principally benefit compute shaders and other cases.
SDMA copies can speed-up transfers over PCI Express, it's done asynchronously so graphics work can still happen concurrently, and there is low driver overhead to the copies, but ultimately should benefit compute shaders and other select use-cases.
The GFX9 SDMA enablement in Mesa 20.0-devel only enables SDMA copies by default for APUs (or graphics processors otherwise lacking dedicated video RAM) or when the force DMA flag is enabled with AMD_DEBUG=testdma.
More details on the SDMA copy caveats and other criteria via the now closed MR.
SDMA copies can speed-up transfers over PCI Express, it's done asynchronously so graphics work can still happen concurrently, and there is low driver overhead to the copies, but ultimately should benefit compute shaders and other select use-cases.
The GFX9 SDMA enablement in Mesa 20.0-devel only enables SDMA copies by default for APUs (or graphics processors otherwise lacking dedicated video RAM) or when the force DMA flag is enabled with AMD_DEBUG=testdma.
More details on the SDMA copy caveats and other criteria via the now closed MR.
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