问题
My problem is that my GameScene starts with about double the nodes and draws count and 40 fps for several seconds. This problem appears only on my iPad (mini retina) while on my iPhone (5) the game runs smoothly from the start although the nodes are still a lot more than what it should be
回答1:
This 40fps problem is an issue within the iOS frameworks. It's created by some kind of throttling (by iOS).
Perhaps this throttling was designed to give a more consistent experience for an app struggling to maintain 60fps. But nobody knows.
Apple has never commented on it.
It became prevalent throughout the rollout of iOS 9 in Scene Kit, Sprite Kit and Metal. But has been seen within OpenGL ES locked projects, too.
However it was noticed in previous versions of iOS, too. Particularly within apps/games using CADisplayLink.
//Don't worry about those asking for code, you're right in your assumption that something is wrong that's not pertinent to your code.
Here's a deeper examination of a similar issue (probably from the same route cause) within Scene Kit: Inconsistent SceneKit framerate
来源：https://stackoverflow.com/questions/34841648/spritekit-scene-with-low-fps-on-start