SIPE: A TSS/360 software measurement technique

• Authors: W. R. Deniston
• Venue: ACM '69 Proceedings of the 1969 24th national conference
• Year: 1969

Analysis of the operation of a large-scale, complex operating system requires data that can be obtained only from “inside” the system as it is running. Such data can supplement that obtained via hardware measurements, and can support simulation models by providing realistic calibration data. The primary attribute of an internal software measurement technique is that it has access to, and can selectively record, system data stored in memory. This paper describes the methods employed in developing and using such a technique within the IBM System/360 Time Sharing System (TSS/360). A prime consideration in developing a software measurement technique to obtain internal data is that a suitable compromise between resolution and system degradation must be achieved, since the traditional hardware tools for gathering external data provided high resolution without degradation. This was accomplished in the design of the System Internal Performance Evaluation (SIPE) program, which functions as a physical extension to the TSS/360 resident supervisor and records significant events as they occur. When control reaches one of the SIPE “hooks,” which are strategically located in the supervisor, SIPE is entered to record an event. When SIPE has accumulated a quantity of events, it transfers the data to tape. Off-line reduction techniques subsequently permit detailed reconstruction of system data and logical flow. SIPE has been operational for over a year. Experience in using it has indicated that the actual degradation is so small that continuous recording during development, primarily for debugging, can readily be justified.