[Development] why Qt app performance low on qpa eglfs or wayland

[Nancy Zou]

Hi Millan
> You should answer this question yourself and present the results to us. Only you have your specific software/hardware combination setup properly.

I suspect Qt wati for vsyc somewhere because the normal opengl example only cost 14ms (1 vsync) and Qt example openglwindow need 28 ms( just 2 vysnc) 
I think it's strange a simple opengl example run such low fps. 
My fb driver already wait for vsync once in eglSwapBuffers. So Qt don't need wait it. So I want to find out where qt hung. Whether Qt wait for some events somewhere?

>Try Linux' `perf top` e.g. or run your application via `perf record --call-graph=dwarf yourapp`. Then do a `perf report` and take a look at the results. Remember to compile your application and all  important dependencies (esp. Qt) in release mode with debug symbols, i.e. at least use the compile flags `-O2 -g`.

I have done this in qmake.


Thank you

Best Regards
Nancy 


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