1827	 Performance Monitoring in a Time-Sharing System	 A software measurement facility which is part of a general purpose time-sharing system is described. The Date Collection Facility DCF has been implemented in the Michigan Terminal System MTS for the System model . It exists for the purpose of monitoring operating system and user program behavior and performance. The overall structure of MTS is outlined in order to explain the implementation of the DCF. Events in the system are identified and recorded from within the supervisor and dumped to magnetic tape by an auxiliary program for off-line processing. Events in user programs which are unrelated to system actions are recorded with a supervisor call. The time of occurrence of each event is accurately recorded and data items are further identified by job and type. The overhead associated with data collection and its interference with normal jobs is carefully analyzed and both are shown to be minimal. Several examples are given of information obtained with the facility and of applications in which it has been useful. Some general guidelines are offered for the construction of future monitoring programs. performance monitoring performance measurement program behavior performance data multiprogramming performance software measurement time-sharing performance system evaluation software monitor software instrumentation
