UpdateScreenManagerAndInput, which takes almost cpu usage in a profiler

I ran into this problem in one of my projects recently and thought I'd share my solution since there doesn't seem to be a whole lot of information online about this.

I'm not sure if this problem is specifically related to referencing the Input class or Image class, but here was my solution. In my input manager's Update method I was calling Input.GetMouseButtonUp(0) and then executing a block of code. After optimizing that block of code (specifically, I removed a line which was updating an Image color via Image.color = someColor which seemed to be causing the majority of the performance hit) the UpdateScreenManagerAndInput spikes I was experiencing in the profiler went away and my game's FPS returned to normal.

I hope that helps you and/or anyone else who is experiencing this tricky problem!

From a "UpdateScreenManagerAndInput & Unaccounted Time" forum thread:

I just so happened to have plugged a PS3 controller into my MacBook before this happened. So I unplugged it. Everything returned to normal.

Try unplugging some USB devices!