Struggling

Last week was XDC. I did too much Wayland, and now I’ve been stricken with a plague for my hubris.

I have some updates, but I lack the ability to fully capture the exploits of Mesa’s most sane developer in the ten minutes I’m awake every day. In the meanwhile, let’s take a look another potential example of great hubris.

Hm.

Have you ever made a decision that seemed great at the time but then you realized later it was actually maybe not that great? Like, maybe it was actually really, uh, well, not dumb since nobody reading this blog would do something like that, but not…smart. And everyone else was kinda going along with your decision and trusting that you knew what you were talking about because let’s face it, you’re smart. Everyone knows how smart you are. That’s why they trust you to make these decisions.

Long-time SGC readers know I’m not one to make decisions of any kind, but we all remember that time Microsoft famously introduced Work Graphs to D3D and also (quietly) deprecated ExecuteIndirect. The argument was compelling: why not just move all the work to the GPU?

Haters described Work Graphs as just another attempt by the driver cartel to blame bugs on app developers by making tooling impossible. The rest of us were all in—We jumped on that bandwagon like it was the last triangle in the pipe before a crash. It wasn’t long before the high-powered players were aboard:

• NVIDIA
• AMD

Details were light at this stage. There were no benchmarks, no performance numbers, no games or applications using Work Graphs, but everyone trusted Microsoft. Everyone knew the idea of this tech was sound, that it had to be faster.

Microsoft doubled down: Work Graphs would support mesh nodes for drawing!

Other graphics wizards began to get involved. The developerverse was in a tizzy. Everyone wanted in on the action.

The hype train had departed the station.

Hm?

Six months after GDC, the first notable performance figures for Work Graphs were blogged about by AAA graphics rockstar, Kostas Anagnostou. I was at a Khronos F2F when it happened, and the number of laptop screens open to the post when it dropped was nonzero. Very nonzero.

At best, the figures were whelming.

Still there was no real analysis of Work Graph performance in comparison to alternative solutions. Haters will say I’m biased after recently shipping Vulkan’s device generated commands extension, but this was going to ship regardless since vkd3d-proton requires cross-vendor compatibility for ExecuteIndirect functionality used in games like Halo Infinite and Starfield. I’m all about the numbers. Show me the graphs. The perf graphs, that is.

Fortunately, friend of the blog and veteran vertex wrangler, Hans-Kristian Arntzen, always has my back. He’s spent the past few months heroically writing vkd3d-proton emulation for Work Graphs, and he has recently posted his findings to an obscure README in that repository.

READ IT. SERIOUSLY. YES, THIS IS A FULL PAGE-WIDTH LINK SO YOU CAN’T POSSIBLY MISS IT.

If you’re just here for the quick summary (which you shouldn’t be considering how much time he has spent making charts and graphs, and taking screenshots, and summing everything up in bite-sized morsels for easy consumption):

• Across the board, Work Graph performance is not very exciting
• Emulation with core Vulkan compute shader features is up to 3x faster
• Comparison test cases against ExecuteIndirect (which show EI being worse) do not effectively leverage that functionality, as noted by Hans-Kristian nearly six months ago

The principle of charity requires taking serious claims in the best possible light. This should have yielded robust, powerful ExecuteIndirect benchmark usage (and even base compute/mesh shader usage) to provide competitive benchmarks against Work Graph functionality. At the time of writing, those benchmarks have yet to materialize, and the only test cases are closer to strawmen that can be held up for an easy victory.

I’m not saying that Work Graphs are inherently bad.

Yet.

At this point, however, I haven’t seen compelling evidence which validates the hype surrounding the tech. I haven’t seen great benchmarks and demos. Maybe it’s a combination of that and still-improving driver support. Maybe it’s as-yet available functionality awaiting future hardware. In any case, I haven’t seen a strong, fact-based technical argument which proves, beyond a doubt, that this is the future of graphics.

Before anyone else tries to jump on the Work Graph hype train, I think we owe it to ourselves to thoroughly interrogate this new paradigm and make sure it provides the value that everyone expects.