how to get the rate(top/ps) of cpu and the usage of memory?

Question

Can i do that? or It's a private API?

Answer 1

No, there are not API's for this.

http://stackoverflow.com/questions/1563935/how-to-display-iphone-free-memory-and-how-to-free-iphone-memory

Answer 2

You can get the total memory usage of your app and total free memory in the system with the code posted in this other question.

Of course, free memory varies depending on what background processes are running at the time and what's in the autorelease pool(s) at the moment, but it does give you some idea.