Simple Vulkan rendering very slow on AMD (shows 50% Copy workload in Windows Task-Manager)

[drywolf]

Hi, I am trying to figure out why our Vulkan application is running much slower on AMD GPUs when compared against NVidia GPUs. I have already reduced our code to a somewhat minimal example, which is just running an empty VK render-pass and simply clears the color-image (no draw-commands)

This example app is running with ~13000 FPS on my NVidia RTX 2080 Ti, but is running at just ~350 FPS on my AMD RX 5700 XT card.

In our production code we are using Vulkan for offscreen/headless rendering, but I also reproduced the same lack of performance when using a VK window + swapchain.

This is my Github repo with two "minimal" VK apps for offscreen & window rendering to show the performance issue: https://github.com/drywolf/vsg_amd_perf

Also there is already some discussion about this topic in the following VulkanSceneGraph issue: https://github.com/vsg-dev/VulkanSceneGraph/issues/1208

The big difference between the AMD and NVidia GPU that I was able to see already in the Windows Task-Manager, the AMD rendering of an empty window/empty framebuffer is producing a ~60% "Copy" workload. While on the NVidia GPU there is 0% Copy workload and 30x higher FPS.

GPU	Task-Mgr 3D Workload	Task-Mgr Copy Workload	FrameRate
NVidia RTX 2080 Ti	2%	0%	13000 FPS
AMD RX 5700 XT	10% - 50%	50% - 60%	350 FPS

I already tried lots of experiments in the Vulkan code & RenderPass / Clear parameters, but so far the performance is always the same. (the most recent thing I tried was to make sure the RenderPass clear parameters were set to 0, 0, 0, 0 as mentioned here, but this also did not change the performance)

[owenzhangzhengzhong]

Thanks @drywolf, I've created internal ticket tracking this issue, we'll be looking into this.

[drywolf]

Thanks @owenzhangzhengzhong 👍