High GPU usage in Windows

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Qt applications which run 3D drawing on a constant rate in Windows can all of a sudden start utilizing an unreasonable portion of GPU resources, even if the rendering task remains the same. This behavior can be observed with any Qt application utilizing 3D capabilities (OpenGL scene, QML with animations).

Steps to reproduce:

• Open Qt Creator, select "OpenGL Window Example" in Examples and run the application
• Open Task Manager and observe GPU usage
• If nothing happens, try maximizing and minimizing the application window, and activating and moving other windows around
• Sometimes it takes up to 30 seconds before the GPU usage increases
• This behavior can be observed both when the window is in normal state, or in maximized state

What is also notable, is that it's not only the application that consumes the GPU, but Desktop Window Manager participates always as well (see attachments).

I've tested this with various compilers (MSVC, MinGW), and Qt versions (5.10, 5.12, 5.15), and as standalone executable, but the problem persists.

This behavior is somewhat sporadic. Sometimes the GPU usage remains high throughout the entire runtime of the application, while sometimes GPU usage jumps up and down with ~10 intervals (see attachments).

The GPU in question is NVIDIA GeForce GTX 1070Ti. Although I've received reports of high GPU usage in other Windows systems, therefore this issue is most likely not limited to a single PC.