Waiter, there's an IES in my DGC!
Finally! Yesterday Khronos published Vulkan 1.3.296 including VK_EXT_device_generated_commands. Thousands of engineering hours seeing the light of day, and awesome news for Linux gaming.
Device-Generated Commands, or DGC for short, are Vulkan’s equivalent to ExecuteIndirect in Direct3D 12. Thanks to this extension, originally based on a couple of NVIDIA vendor extensions, it will be possible to prepare sequences of commands to run directly from the GPU, and executing those sequences directly without any data going through the CPU. Also, Proton now has a much-more official leg to stand on when it has to translate ExecuteIndirect from D3D12 to Vulkan while you run games such as Starfield.
The extension not only provides functionality equivalent to ExecuteIndirect. It goes beyond that and offers more fine-grained control like explicit preprocessing of command sequences, or switching shaders and pipelines with each sequence thanks to something called Indirect Execution Sets, or IES for short, that potentially work with ray tracing, compute and graphics (both regular and mesh shading).
As part of my job at Igalia, I’ve implemented CTS tests for this extension and I had the chance to work very closely with an awesome group of developers discussing specification, APIs and test needs. I hope I don’t forget anybody and apologize in advance if so.
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Mike Blumenkrantz, of course. Valve contractor, Super Good Coder and current OpenGL Working Group chair who took the initial specification work from Patrick Doane and carried it across the finish line. Be sure to read his blog post about DGC. Also incredibly important for me: he developed, and kept up-to-date, an implementation of the extension for lavapipe, the software Vulkan driver from Mesa. This was invaluable in allowing me to create tests for the extension much faster and making sure tests were in good shape when GPU driver authors started running them.
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Spencer Fricke from LunarG. Spencer did something fantastic here. For the first time, the needed changes in the Vulkan Validation Layers for such a large extension were developed in parallel while tests and the spec were evolving. His work will be incredibly useful for app developers using the extension in their games. It also allowed me to detect test bugs and issues much earlier and fix them faster.
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Samuel Pitoiset (Valve contractor), Connor Abbott (Valve contractor), Lionel Landwerlin (Intel) and Vikram Kushwaha (NVIDIA) providing early implementations of the extension, discussing APIs, reporting test bugs and needs, and making sure the extension works as good as possible for a variety of hardware vendors out there.
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To a lesser degree, most others mentioned as spec contributors for the extension, such as Hans-Kristian Arntzen (Valve contractor), Baldur Karlsson (Valve contractor), Faith Ekstrand (Collabora), etc, making sure the spec works for them too and makes sense for Proton, RenderDoc, and drivers such as NVK and others.
If you’ve noticed, a significant part of the people driving this effort work for Valve and, from my side, the work has also been carried as part of Igalia’s collaboration with them. So my explicit thanks to Valve for sponsoring all this work.
If you want to know a bit more about DGC, stay tuned for future talks about this topic. In about a couple of weeks, I’ll present a lightning talk (5 mins) with an overview at XDC 2024 in Montreal. Don’t miss it!