So what I'm somewhat curious about is if this isn't an argument for heterogeneous GPU usage. Schedule this on an iGPU while the main GPU is busy. The main downs

So what I'm somewhat curious about is if this isn't an argument for heterogeneous GPU usage. Schedule this on an iGPU while the main GPU is busy. The main downside, as I alluded to above, would be memory bandwidth unless there is a good on die cache for the iGPU or it has dedicated memory. That said with a multi-gpu setup you might also have another card you could use. The other thought I have is that it's very difficult to keep the GPU 100% saturated in my experience. If the vertex count is high enough to make the PCI-e transition worth it (and it would seem to be), then you can potentially cycle steal a bit on the main GPU. This will potentially slow down the main render but speed up the overall. This would be particularly true if you can rebind the resource back for use in the main render pipe.