Paradyn Week – April 14, 2004 – Madison, WI DPOMP: A DPCL Based Infrastructure for Performance Monitoring of OpenMP Applications Bernd Mohr Forschungszentrum Jülich * Work done while authors were at IBM Research * Seetharami Seelam University of Texas El Paso Luiz DeRose Cray Inc. *

DPOMP: A DPCL Based Infrastructure for Performance Monitoring of OpenMP Applications Luiz DeRose 2 Outline  What is POMP  What is DPCL  IBM compiler and run-time library features that makes dPOMP possible  Implementation  POMP not supported features (and why)  Probe libraries  POMPROF  KOJAK  Conclusions

DPOMP: A DPCL Based Infrastructure for Performance Monitoring of OpenMP Applications Luiz DeRose 3 “Standard” OpenMP Monitoring API?  Problem:  OpenMP (unlike MPI) does not define standard monitoring interface  OpenMP is defined mainly by directives/pragmas Solution:  POMP: OpenMP Monitoring Interface  Joint Development Forschungszentrum Jülich University of Oregon  Presented at EWOMP’01, LACSI’01 and SC’01 “The Journal of Supercomputing”, 23, Aug

DPOMP: A DPCL Based Infrastructure for Performance Monitoring of OpenMP Applications Luiz DeRose 4 What is POMP?  Portable cross-platform/cross-language API to simplify the design and implementation of OpenMP tools  POMP was motivated by the MPI profiling interface (PMPI)  PMPI allows selective replacement of MPI routines at link time Used by most MPI performance tools VampirTrace MP-Profiler User Program Call MPI_Bcast Call MPI_Send MPI Library MPI_Bcast PMPI_Send MPI_Send MPI Library MPI_Bcast PMPI_Send MPI_Send Profiling Library MPI_Send

DPOMP: A DPCL Based Infrastructure for Performance Monitoring of OpenMP Applications Luiz DeRose 5 A Brief History of OpenMP Instrumentation  POMP1 OpenMP performance monitoring interface  Forschungszentrum Jülich, University of Oregon  Published at "The Journal of Supercomputing", Vol. 23,  European IST Project INTONE  Development of OpenMP tools (includes Monitoring interface)  Pallas, CEPBA, Royal Inst. Of Technology, Tech. Univ. Dresden   Intel KAI Software Laboratory (KSL) - POMP  Development of OpenMP monitoring interface inside ASCI  Based on POMP, but further developed in other directions  Joint proposal presented at EWOMP’02  POMP2 == POMP

DPOMP: A DPCL Based Infrastructure for Performance Monitoring of OpenMP Applications Luiz DeRose 6 POMP Proposal  Three groups of events  OpenMP constructs and directives/pragmas Enter/Exit around each OpenMP construct Begin/End around associated body Special case for parallel loops: ChunkBegin/End, IterBegin/End, or IterEvent instead of Begin/End “Single” events for small constructs like atomic or flush  OpenMP API calls Enter/Exit events around omp_set_*_lock() functions “single” events for all API functions  User functions and regions  Allows application programmers to specify and control amount of instrumentation

DPOMP: A DPCL Based Infrastructure for Performance Monitoring of OpenMP Applications Luiz DeRose 7 1: int main() { 2: int id; 3: 4: #pragma omp parallel private(id) 5: { 6: id = omp_get_thread_num(); 7: printf("hello from %d\n", id); 8: } 9: } Example: Standard Instrumentation 1: int main() { 2: int id; 3: 4: #pragma omp parallel private(id) 5: { 6: id = omp_get_thread_num(); 7: printf("hello from %d\n", id); 8: } 9: } *** POMP_Init(); *** POMP_Finalize(); *** { POMP_handle_t pomp_hd1 = 0; *** int32 pomp_tid = omp_get_thread_num(); *** int32 pomp_tid = omp_get_thread_num(); *** } *** POMP_Parallel_enter(&pomp_hd1, pomp_tid, -1, 1, *** "49*type=pregion*file=demo.c*slines=4,4*elines=8,8**"); *** POMP_Parallel_begin(pomp_hd1, pomp_tid); *** POMP_Parallel_end(pomp_hd1, pomp_tid); *** POMP_Parallel_exit(pomp_hd1, pomp_tid);

DPOMP: A DPCL Based Infrastructure for Performance Monitoring of OpenMP Applications Luiz DeRose 8 Dynamic Performance Monitoring Interface for OpenMP  Collaboration with Forschungszentrum Jülich  Motivation:  POMP under review by the OpenMP ARB! May take too long to be implemented (if accepted)  Approach  A POMP implementation based on dynamic probes Built on top of DPCL Modifies the binary with performance instrumentation No source code or re-compilation required

DPOMP: A DPCL Based Infrastructure for Performance Monitoring of OpenMP Applications Luiz DeRose 9 What Is DPCL?  IBM’s Dynamic Probe Class Library  Based on DynInst and Paradyn  Allows tools to insert data, functions, and code patches (probes) into a program dynamically  Call site  Call entry  Call exit  Probes can collect and report program information, program state, or modify the program execution  Probes may be placed at specific locations in the program and can be activated  Whenever execution reaches that location  By expiration of a timer  Exactly once

DPOMP: A DPCL Based Infrastructure for Performance Monitoring of OpenMP Applications Luiz DeRose 10 A() { } OMP loop Source code main() { } A() OMP parallel OMP end parallel DPOMP Instrumentation  The IBM compiler and run-time library run-time library Compiler generated A() { } xlf_Par main() { } A() master thread { } xlf_DoPar all threads do I=start,end loop body enddo { } POMP_Parallel_enter POMP_Parallel_exit POMP_Parallel_begin POMP_Parallel_end POMP_Loop_enter POMP_Loop_exit POMP_Loop_chunk_begin POMP_Loop_chunk_end POMP_Functionl_enter POMP_Functionl_exit

DPOMP: A DPCL Based Infrastructure for Performance Monitoring of OpenMP Applications Luiz DeRose 11 DPOMP Usage % dpomp  Input parameters  OpenMP application (or mixed-mode)  POMP compliant monitoring library  List of user functions to instrument (optional) dpomp [-f function.lst] libpomp a.out

DPOMP: A DPCL Based Infrastructure for Performance Monitoring of OpenMP Applications Luiz DeRose 12 DPOMP Instrumentation  Amount of instrumentation can be controlled  By the tool builder Set of POMP calls available in the monitoring library and/or  By the user Environment variables  Events instrumented by default:  All OpenMP constructs  All user functions called in the main program  All MPI Calls  Once the instrumentation is finished, the modified program is executed

DPOMP: A DPCL Based Infrastructure for Performance Monitoring of OpenMP Applications Luiz DeRose 13 Limitations  63 out of 68 POMP events supported !  Limitations due to compiler issues  POMP_Loop_iter_(begin, or end, or event)  POMP_Implicit_barrier_(end, or exit)  OMP Parallel Loop NOT = OMP Parallel / OMP Loop  Compile Time Context (CTC) hasFirstPrivate, hasLastPrivate, hasNowait, hasCopyin, schedule, hasOrdered, and hasCopypriv not available  Limitations due to DPCL issues  Loop iteration values (init, final, incr, chunk)  Other Limitations  C++ not support

DPOMP: A DPCL Based Infrastructure for Performance Monitoring of OpenMP Applications Luiz DeRose 14 POMP Profiler (POMPROF)  Generates a detailed profile describing overheads and time spent by each thread in three key regions of the parallel application:  Parallel regions  OpenMP loops inside a parallel region  User defined functions  Profile data is presented in the form of an XML file that can be visualized with PeekPerf

DPOMP: A DPCL Based Infrastructure for Performance Monitoring of OpenMP Applications Luiz DeRose 15 POMP Profiler (pomprof)

DPOMP: A DPCL Based Infrastructure for Performance Monitoring of OpenMP Applications Luiz DeRose 16 POMP Profiler (II)

DPOMP: A DPCL Based Infrastructure for Performance Monitoring of OpenMP Applications Luiz DeRose 17 KOJAK POMP Library (Forschungszentrum Juelich)  POMP monitoring library which generates EPILOG event traces  Processed by KOJAK’s automatic event tracer analyzer EXPERT Performance Property: Which type of behavior caused the problem? Call Tree: Where in the source code? In which context? Location: How is the problem distributed across the machine? Color Scale: How severe is the problem?

DPOMP: A DPCL Based Infrastructure for Performance Monitoring of OpenMP Applications Luiz DeRose 18 EPILOG Trace Converted to VTF3 (FZ Juelich)  EPILOG-to-VTF3  Maps OpenMP constructs into VAMPIR symbols and activities

DPOMP: A DPCL Based Infrastructure for Performance Monitoring of OpenMP Applications Luiz DeRose 19 Conclusions  DPCL based implementation of the POMP performance monitoring interface for OpenMP  Easy to use  Two POMP Libraries  KOJAK POMP Library  POMP Profiler Library or build your own library