TOPAS - Automatic Performance Statistics Collection on the CRAY T3E

TOPAS is a tool to automatically and transparently monitor usage and performance of every parallel job executed on a CRAY T3E. We have modified the UNICOS/mk compiler wrapper scripts to automatically link the TOPAS measurement module to every user application whenever it is recompiled. No modification is necessary in the user’s program or build procedures. At run-time, two PEs of the parallel application are picked to actually perform the measurement for the parallel job as a whole. The measurement consists of executing special code immediately before and after the execution of the program. So there is no measurement overhead during the execution of the application itself. The TOPAS module is very simple (about 250 lines of code). It is based on the Performance Counter Library (PCL), a common interface for portable performance counting on microprocessors, also developed at NIC/ZAM.Through environment variables, users can request the printing of the recorded information at the end of the execution, choose to measure integer, load, or store operations instead of floating point, and specify the PEs which should be used for performing the measurement.In addition to the TOPAS measurement module, we implemented a tool which allows a system administrator to calculate interesting statistics like the typical MFlop rates achieved by user programs, as well as programming language and message passing library usage from this data. Most of this information is not available through regular T3E system accounting