From apple's doc and session,I think CAShapeLayer should render in render server when composited.And if shouldRasterize is disabled, the path should render every frame.
But when I profile a layer with a very complex path, seems not true. I can see the render is not happen on app side, but it is not happen every frame when I disabled rasterize, it only happen when I change the path.
Apple now cache the rendered bitmap all the time, this may consume some memory?
If apple cache the bitmap, I think it's conflict with the session above.
The path rasterization process of the CAShapeLayer happens on the render server side, not on the client (app) side.