Tracing application program execution on the Cray X-MP and Cray 2

A tracing library for the Cray X-MP and Cray 2 supercomputers has been developed that supports the low-overhead capture of execution events for sequential and multitasked programs. This library has been extended to use the automatic instrumentation facilities on these machines, allowing trace data from routine entry and exit, and other program segments to be captured. To assess the utility of the trace-based tools, three of the Perfect Benchmark codes have been tested in scalar and vector models with the tracing instrumentation. In addition to computing summary execution statistics from the traces, interesting execution dynamics appear when studying the trace histories. It is also possible to compare codes across the two architectures by correlating the event traces. It is concluded that adding tracing support in Cray supercomputers can have significant returns in improved performance characterization and evaluation.<>