run time vs runtime

run time

noun
  • The length of a film, television program or audio track in minutes, usually with end credits included 

  • The amount of time during which a program is executing. 

  • A software component designed to support the execution of computer programs. 

  • The stage during which a program is executing. 

runtime

How often have the words run time and runtime occurred in a corpus of books? (source: Google Ngram Viewer )