Profiling under ELXSI UNIX

Dynamic program measurement, commonly known as profiling, is a highly desirable tool for any programming environment. By measuring the actual behaviour of programs, tuning efforts can focus on those components that account for the significant part of the execution time. The traditional UNIX profiling mechanism is based on sampling the program counter. In the ELXSI implementation of UNIX System V, this mechanism is not appropriate. Execution profiling of user programs has instead been implemented by exploiting the high precision timer in the ELXSI 6400 architecture. This per‐process timer makes it possible to replace interrupt‐driven sampling as the source of timing information.