cpu overload - fps down...

hello
I made a very complex dash on the first page with many objects and complex calculations in real time.
it happens that, only with the first page being displayed, i have a very consistent drop in fps due to a load on the cpu.
it happens only with the first page while with the other much simpler pages it does not.
the question is how can i identify the component or calculation that is overloading the cpu in order to optimise or redesign it?