title: Return stack buffer?
body: <p>As I understood, Return Stack Buffer only supports 4 to 16 entries (from wiki: <a href="http://en.wikipedia.org/wiki/Branch_predictor#Prediction_of_function_returns" rel="nofollow noreferrer">http://en.wikipedia.org/wiki/Branch_predictor#Prediction_of_function_returns</a>) and is not pair of key-value(based on indexing by position of ret instruction). Is it true?
  What happens to RSB when context switch happens?</p>
  <p>Suppose we got into 50 functions which aren't returned in a CPU with return stack buffer length of 16, what happens after it? Does it mean all predictions fail? Can you illustrate it? Is this scenario the same in recursive function calls?</p>