1. October 18, 2001 LACSI Symposium, Santa Fe, NM1 Towards Scalable Cross-Platform Application Performance Analysis -- Tool Goals and Progress Shirley Moore shirley@cs.utk.edu

2. October 18, 2001 LACSI Symposium, Santa Fe, NM2 Scalability Issues Code instrumentation –Hand instrumentation too tedious for large codes Runtime control of data collection Batch queueing systems –Cause problems for interactive tools Tracefile size and complexity Data analysis

3. October 18, 2001 LACSI Symposium, Santa Fe, NM3 Cross-platform Issues Goal: similar user interfaces across different platforms Tools necessarily rely on platform- dependent substrates – e.g., for accessing hardware counters. Standardization of interfaces and data formats promotes interoperability and allows design of portable tools.

4. October 18, 2001 LACSI Symposium, Santa Fe, NM4 Where is Standardization Needed? Performance data –Trace records vs. summary statistics –Data format –Data semantics Library interfaces –Access to hardware counters –Statistical profiling –Dynamic instrumentation

5. October 18, 2001 LACSI Symposium, Santa Fe, NM5 Standardization? (cont.) User interfaces –Common set of commands –Common functionality Timing routines Memory utilization information

6. October 18, 2001 LACSI Symposium, Santa Fe, NM6 Parallel Tools Consortium http://www.ptools.org/ Interaction between vendors, researchers, and users Venue for standardization Current projects –PAPI –DPCL

7. October 18, 2001 LACSI Symposium, Santa Fe, NM7 Hardware Counters Small set of registers that count events, which are occurrences of specific signals related to the processor’s function Monitoring these events facilitates correlation between the structure of the source/object code and the efficiency of the mapping of that code to the underlying architecture.

8. October 18, 2001 LACSI Symposium, Santa Fe, NM8 Goals of PAPI Solid foundation for cross platform performance analysis tools Free tool developers from re- implementing counter access Standardization between vendors, academics and users Encourage vendors to provide hardware and OS support for counter access Reference implementations for a number of HPC architectures Well documented and easy to use

9. October 18, 2001 LACSI Symposium, Santa Fe, NM9 PAPI Implementation Tools!!! PAPI Low Level PAPI High Level Hardware Performance Counter Operating System Kernel Extension PAPI Machine Dependent Substrate Machine Specific Layer Portable Layer

10. October 18, 2001 LACSI Symposium, Santa Fe, NM10 PAPI Preset Events Proposed standard set of events deemed most relevant for application performance tuning Defined in papiStdEventDefs.h Mapped to native events on a given platform –Run tests/avail to see list of PAPI preset events available on a platform

11. October 18, 2001 LACSI Symposium, Santa Fe, NM11 Statistical Profiling PAPI provides support for execution profiling based on any counter event. PAPI_profil() creates a histogram by text address of overflow counts for a specified region of the application code. Used in vprof tool from Sandia Lab

12. October 18, 2001 LACSI Symposium, Santa Fe, NM12 PAPI Reference Implementations Linux/x86, Windows 2000 –Requires patch to Linux kernel, driver for Windows Linux/IA-64 Sun Solaris 2.8/Ultra I/II IBM AIX 4.3+/Power –Contact IBM for pmtoolkit SGI IRIX/MIPS Compaq Tru64/Alpha Ev6 & Ev67 Requires OS device driver patch from Compaq Per-thread and per-process counts not possible Extremely limited number of events Cray T3E/Unicos

13. October 18, 2001 LACSI Symposium, Santa Fe, NM13 PAPI Future Work Improve accuracy of hardware counter and statistical profiling data –Microbenchmarks to measure accuracy (Pat Teller, UTEP) –Use hardware support for overflow interrupts –Use Event Address Registers (EARs) where available Data structure based performance counters (collaboration with UMd) –Qualify event counting by address range –Page level counters in cache coherence hardware

14. October 18, 2001 LACSI Symposium, Santa Fe, NM14 PAPI Future (cont.) Memory utilization extensions (following list suggested by Jack Horner, LANL) –Memory available on a node –Total memory available/used –High-water-mark memory used by process/thread –Disk swapping by process –Process-memory locality –Location of memory used by an object Dynamic instrumentation – e.g., PAPI probe modules

15. October 18, 2001 LACSI Symposium, Santa Fe, NM15 For More Information http://icl.cs.utk.edu/projects/papi/ –Software and documentation –Reference materials –Papers and presentations –Third-party tools –Mailing lists

16. October 18, 2001 LACSI Symposium, Santa Fe, NM16 DPCL Dynamic Probe Class Library Built of top of IBM version of University of Maryland’s dyninst Current platforms –IBM AIX –Linux/x86 (limited functionality) Dyninst ported to more platforms but by itself lacks functionality for easily instrumenting parallel applications.

17. October 18, 2001 LACSI Symposium, Santa Fe, NM17 Infrastructure Components? Parsers for common languages Access to hardware counter data Communication behavior instrumentation and analysis Dynamic instrumentation capability Runtime control of data collection and analysis Performance data management

18. October 18, 2001 LACSI Symposium, Santa Fe, NM18 Case Studies Test tools on large-scale applications in production environment Reveal limitations of tools and point out areas where improvements are needed Develop performance tuning methodologies for large-scale codes

19. October 18, 2001 LACSI Symposium, Santa Fe, NM19 PERC: Performance Evaluation Research Center Developing a science for understanding performance of scientific applications on high-end computer systems.Developing a science for understanding performance of scientific applications on high-end computer systems. Developing engineering strategies for improving performance on these systems.Developing engineering strategies for improving performance on these systems. DOE Labs: ANL, LBNL, LLNL, ORNLDOE Labs: ANL, LBNL, LLNL, ORNL Universities: UCSD, UI-UC, UMD, UTKUniversities: UCSD, UI-UC, UMD, UTK Funded by SciDAC: Scientific Discovery through Advanced ComputingFunded by SciDAC: Scientific Discovery through Advanced Computing

20. October 18, 2001 LACSI Symposium, Santa Fe, NM20 PERC: Real-World Applications High Energy and Nuclear PhysicsHigh Energy and Nuclear Physics –Shedding New Light on Exploding Stars: Terascale Simulations of Neutrino-Driven SuperNovae and Their NucleoSynthesis –Advanced Computing for 21st Century Accelerator Science and Technology Biology and Environmental ResearchBiology and Environmental Research –Collaborative Design and Development of the Community Climate System Model for Terascale Computers Fusion Energy SciencesFusion Energy Sciences –Numerical Computation of Wave-Plasma Interactions in Multi- dimensional Systems Advanced Scientific ComputingAdvanced Scientific Computing –Terascale Optimal PDE Solvers (TOPS) –Applied Partial Differential Equations Center (APDEC) –Scientific Data Management (SDM) Chemical SciencesChemical Sciences –Accurate Properties for Open-Shell States of Large Molecules …and more……and more…

21. October 18, 2001 LACSI Symposium, Santa Fe, NM21 Parallel Climate Transition Model Components for Ocean, Atmosphere, Sea Ice, Land Surface and River Transport Developed by Warren Washington’s group at NCAR POP: Parallel Ocean Program from LANL CCM3: Community Climate Model 3.2 from NCAR including LSM: Land Surface Model ICE: CICE from LANL and CCSM from NCAR RTM: River Transport Module from UT Austin Fortran 90 with MPI

22. October 18, 2001 LACSI Symposium, Santa Fe, NM22 PCTM: Parallel Climate Transition Model Flux Coupler Land Surface Model Ocean Model Atmosphere Model Sea Ice Model Sequential Execution of Parallelized Modules River Model

23. October 18, 2001 LACSI Symposium, Santa Fe, NM23 PCTM Instrumentation Vampir tracefile in tens of gigabytes range even for toy problem Hand instrumentation with PAPI tedious UIUC working on SvPablo instrumentation Must work in batch queueing environment Plan to try other tools –MPE logging and jumpshot –TAU –VGV?

24. October 18, 2001 LACSI Symposium, Santa Fe, NM24 In Progress Standardization and reference implementations for memory utilization information (funded by DoD HPCMP PET, Ptools-sponsored project) Repositories of application performance evaluation case studies (e.g., SciDAC PERC) Portable dynamic instrumentation for parallel applications (DOE MICS project – UTK, UMd, UWisc) Increased functionality and accuracy of hardware counter data collection (DoD HPCMP, DOE MICS)

25. October 18, 2001 LACSI Symposium, Santa Fe, NM25 Next Steps Additional areas for standardization? –Scalable trace file format –Metadata standards for performance data –New hardware counter metrics (e.g., SMP and DMP events, data-centric counters) –Others?

26. October 18, 2001 LACSI Symposium, Santa Fe, NM26 Next Steps (cont.) Sharing of tools and data –Open source software –Machine and software profiles –Runtime performance data –Benchmark results –Application examples and case studies Long-term goal: common performance tool infrastructure across HPC systems