9410116 Elnozahy The objective of this project is to develop a software monitoring tool that would allow the collection of performance data under realistic workloads and network activities. Unlike other hardware and software monitoring tools, the new tool can collect long execution traces with very little perturbation to the actual system. The duration of monitored execution is estimated to be orders of magnitude longer than has been possible using existing techniques. The implementation takes place entirely in software and relies on the instruction counters that are increasingly becoming common with modern processors. Because the execution of the system is not affected by the monitoring process, the processing can be applied for collecting very long traces while the system is in use. This will permit more ambitious performance studies than have been possible today. The monitoring tool can also be used for debugging purposes during the final testing phases of programs to uncover intermittent errors. These errors, known as Heizenbugs, are the most difficult to discover and are the reason for the perceived unreliability of systems software. ***
