Monday November 12, 2007

Karl Fuerlinger, from the Innovative Computing Laboratory at the University of Tennessee at Knoxville spoke about multicore performance analysis tools at the HPC Consortium meeting here in Reno yesterday. He focused on tools available from academia rather than vendor-supplied tools.

In Karl's view, the vendor tools are powerful, commercially supported, and typically limited to the vendor platform, while academic tools are generally cross-platform, often include advanced or experimental techniques like automated performance analysis and often focus more on high levels of scalability.

Popular academic tools include:

• PAPI, which supports platform-independent access to hardware counters. PAPI has recently been expanded to support access to additional counter types beyond CPU counters. Temperature sensors, HW events on NICs, and instrumentation on memory interfaces are examples. It is possible to generate composite displays showing time-lines of FLOP rates, system temperature, etc.
• TAU has extensive support for tracing and profiling and is considered by many to be the swiss army knife of profiling tools.
• KOJAK/SCALASCA, which offers trace-baed automatic performance analysis capabilities. It does this by automatically searching for patterns of inefficiences in traces with demonstrated scalability to 22K processes.
• Vampir, a tracefile visualization tool for MPI that has applicability f or other programming models as well.
• ompP, a profiling tool for OpenMP and the focus of Karl's work. ompP us es a source-based instrumentation approach to gain independence from specific compilers and runtimes. It is tested and supported on Linux, Solaris, AIX, and with the Pathscale, PGI, gcc, IBM, and Sun compilers. Codes are instrumented to understand how much time is spent in imbalance, synchronization, limited parallelism, and thread management states. Incremental and continuous profiling are supported.

Karl pointed out that these academic tools tend to generally interoperate with each other. For example, PAPI can be used by most of the above tools to access performance counter information. Profiles can be gathered by several of these tools and then visualized with TAU. And trace data collected with these tools can be fed into the KOJAK/SCALASCA automatic trace analysis capabilities. Traces generated from TAU or KOJAK/SCALASCA can be visualized with Vampir.