HUGE performance difference between OpenGLCore and DirectX

I'm using v2020.3.4 with URP 10.4.0 2D Renderer, and vsync off.
If I choose OpenGLCore in the Project Settings, I get 20 FPS, for example. If I choose DirectX, I get 40 FPS, the double.
I've check the profiler and the main difference is that when using OpenGL, there is an entry in the CPU Usage called "Gfx.WaitForPresentOnGfxThread". I remark: vsync is off. This entry appears every N frames, consuming 21 ms.

Here you can see the profile when using DirectX:

And here when using OpenGLCore, at the frame where the suspicious entry appears:


Is this an expected behaviour or a known issue? Why does it happen?

 

Gfx.WaitForPresentOnGfxThread means that the CPU is idling waiting for the GPU to finish rendering the frame. You can turn on the GPU profiler here:



That gives you a GPU profiler, so you might be able to check what's actually taking up the extra time on OpenGL.

 

Thanks for the advice, it was not so useful though:

OpenGLCore


DirectX


(GPU Usage, with Deep Profiling too)