Allen D. Malony Department of Computer and Information Science Performance Research Laboratory University of Oregon Performance Technology for Productive, High-End Parallel Computing

LACSI Outline of Talk  Research motivation  Scalability, productivity, and performance technology  Application-specific and autonomic performance tools  TAU parallel performance system developments  Application performance case studies  New project directions  Discussion

Performance Technology for Productive, High-End Parallel ComputingLACSI Research Motivation  Tools for performance problem solving  Empirical-based performance optimization process  Performance technology concerns characterization Performance Tuning Performance Diagnosis Performance Experimentation Performance Observation hypotheses properties Instrumentation Measurement Analysis Visualization Performance Technology Experiment management Performance database Performance Technology

Performance Technology for Productive, High-End Parallel ComputingLACSI Problem Description  How does our view of this process change when we consider very large-scale parallel systems?  What are the significant issues that will affect the technology used to support the process?  Parallel performance observation is clearly needed  In general, there is the concern for intrusion  Seen as a tradeoff with performance diagnosis accuracy  Scaling complicates observation and analysis  Nature of application development may change  Paradigm shift in performance process and technology?  What will enhance productive application development?

Performance Technology for Productive, High-End Parallel ComputingLACSI Scaling and Performance Observation  Consider “traditional” measurement methods  Profiling: summary statistics calculated during execution  Tracing: time-stamped sequence of execution events  More parallelism  more performance data overall  Performance specific to each thread of execution  Possible increase in number interactions between threads  Harder to manage the data (memory, transfer, storage)  How does per thread profile size grow?  Instrumentation more difficult with greater parallelism?  More parallelism / performance data  harder analysis  More time consuming to analyze and difficult to visualize

Performance Technology for Productive, High-End Parallel ComputingLACSI Concern for Performance Measurement Intrusion  Performance measurement can affect the execution  Perturbation of “actual” performance behavior  Minor intrusion can lead to major execution effects  Problems exist even with small degree of parallelism  Intrusion is accepted consequence of standard practice  Consider intrusion (perturbation) of trace buffer overflow  Scale exacerbates the problem … or does it?  Traditional measurement techniques tend to be localized  Suggests scale may not compound local intrusion globally  Measuring parallel interactions likely will be affected  Use accepted measurement techniques intelligently

Performance Technology for Productive, High-End Parallel ComputingLACSI Role of Intelligence and Specificity  How to make the process more effective (productive)?  Scale forces performance observation to be intelligent  Standard approaches deliver a lot of data with little value  What are the important performance events and data?  Tied to application structure and computational mode  Tools have poor support for application-specific aspects  Process and tools can be more application-aware  Will allow scalability issues to be addressed in context  More control and precision of performance observation  More guided performance experimentation / exploration  Better integration with application development

Performance Technology for Productive, High-End Parallel ComputingLACSI Role of Automation and Knowledge Discovery  Even with intelligent and application-specific tools, the decisions of what to analyze may become intractable  Scale forces the process to become more automated  Performance extrapolation must be part of the process  Build autonomic capabilities into the tools  Support broader experimentation methods and refinement  Access and correlate data from several sources  Automate performance data analysis / mining / learning  Include predictive features and experiment refinement  Knowledge-driven adaptation and optimization guidance  Address scale issues through increased expertise

Performance Technology for Productive, High-End Parallel ComputingLACSI TAU Parallel Performance System Goals  Multi-level performance instrumentation  Multi-language automatic source instrumentation  Flexible and configurable performance measurement  Widely-ported parallel performance profiling system  Computer system architectures and operating systems  Different programming languages and compilers  Support for multiple parallel programming paradigms  Multi-threading, message passing, mixed-mode, hybrid  Support for performance mapping  Support for object-oriented and generic programming  Integration in complex software, systems, applications

Performance Technology for Productive, High-End Parallel ComputingLACSI TAU Performance System Architecture

Performance Technology for Productive, High-End Parallel ComputingLACSI TAU Performance System Architecture

Performance Technology for Productive, High-End Parallel ComputingLACSI TAU Instrumentation Advances  Source instrumentation  Program Database Toolkit (PDT)  automated Fortran 90/95 support (Flint parser, very robust)  statement level support in C/C++ (Fortran soon)  TAU_COMPILER to automate instrumentation process  Automatic proxy generation for component applications  automatic CCA component instrumentation  Python instrumentation and automatic instrumentation  Continued integration with dynamic instrumentation  Update of OpenMP instrumentation (POMP2)  Selective instrumentation and overhead reduction  Improvements in performance mapping instrumentation

Performance Technology for Productive, High-End Parallel ComputingLACSI TAU Measurement Advances  Profiling  Memory profiling  global heap memory tracking (several options)  Callpath profiling  user-controllable calling depth  Improved support for multiple counter profiling  Online profile access and sampling  Tracing  Generation of VTF3 traces files (portable)  Inclusion of hardware performance counts in trace files  Hierarchical trace merging  Online performance overhead compensation  Component software proxy generation and monitoring

Performance Technology for Productive, High-End Parallel ComputingLACSI TAU Performance Analysis Advances  Enhanced parallel profile analysis (ParaProf)  Performance Data Management Framework (PerfDMF)  First release of prototype  Callpath analysis integration in ParaProf  Integration with Vampir Next Generation (VNG)  Online trace analysis  Performance visualization (ParaVis) prototype  Component performance modeling and QoS

Performance Technology for Productive, High-End Parallel ComputingLACSI Component-Based Scientific Applications  How to support performance analysis and tuning process consistent with application development methodology?  Common Component Architecture (CCA) applications  Performance tools should integrate with software  Design performance observation component  Measurement port and measurement interfaces  Build support for application component instrumentation  Interpose a proxy component for each port  Inside the proxy, track caller/callee invocations, timings  Automate the process of proxy component creation  using PDT for static analysis of components  include support for selective instrumentation

Performance Technology for Productive, High-End Parallel ComputingLACSI Flame Reaction-Diffusion (Sandia, J. Ray) CCAFFEINE

Performance Technology for Productive, High-End Parallel ComputingLACSI Component Modeling and Optimization  Given a set of components, where each component has multiple implementations, what is the optimal subset of implementations that solve a given problem?  How to model a single component?  How to model a composition of components?  How to select optimal subset of implementations?  A component only has performance meaning in context  Applications are dynamically composed at runtime  Application developers use components from others  Instrumentation may only be at component interfaces  Performance measurements need to be non-intrusive  Users interested in a coarse-grained performance

Performance Technology for Productive, High-End Parallel ComputingLACSI MasterMind Component (Trebon, IPDPS 2004)

Performance Technology for Productive, High-End Parallel ComputingLACSI Proxy Generator for other Applications  PDT-based proxy component for:  QoS tracking [Boyana, ANL]  Debugging Port Monitor for CCA (tracks arguments)  SCIRun2 Perfume components [Venkat, U. Utah]  Exploring Babel for auto-generation of proxies:  Direct SIDL to proxy code generation  Generating client component interface in C++  Using PDT for generating proxies

Performance Technology for Productive, High-End Parallel ComputingLACSI Earth Systems Modeling Framework  Coupled modeling with modular software framework  Instrumentation for framework and applications  PDT automatic instrumentation  Fortran 95  C / C++  MPI wrapper library for MPI calls  Component instrumentation (using CCA Components)  CCA measurement port manual instrumentation  Proxy generation using PDT and runtime interposition  Significant callpath profiling use by ESMF team

Performance Technology for Productive, High-End Parallel ComputingLACSI Using TAU Component in ESMF/CCA

Performance Technology for Productive, High-End Parallel ComputingLACSI TAU’s Paraprof Profile Browser (ESMF Data) Callpath profile

Performance Technology for Productive, High-End Parallel ComputingLACSI TAU Traces with Counters (ESMF)

Performance Technology for Productive, High-End Parallel ComputingLACSI Visualizing TAU Traces with Counters/Samples

Performance Technology for Productive, High-End Parallel ComputingLACSI Uintah Computational Framework (UCF)  University of Utah, Center for Simulation of Accidental Fires and Explosions (C-SAFE), DOE ASCI Center  UCF analysis  Scheduling  MPI library  Components  Performance mapping  Use for online and offline visualization  ParaVis tools F 500 processees

Performance Technology for Productive, High-End Parallel ComputingLACSI Scatterplot Displays  Each point coordinate determined by three values: MPI_Reduce MPI_Recv MPI_Waitsome  Min/Max value range  Effective for cluster analysis Relation between MPI_Recv and MPI_Waitsome

Performance Technology for Productive, High-End Parallel ComputingLACSI Online Unitah Performance Profiling  Demonstration of online profiling capability  Colliding elastic disks  Test material point method (MPM) code  Executed on 512 processors ASCI Blue Pacific at LLNL  Example  Bargraph visualization  MPI execution time  Performance mapping  Multiple time steps

Performance Technology for Productive, High-End Parallel ComputingLACSI Miranda Performance Analysis (Miller, LLNL)  Miranda is a research hydrodynamics code  Fortran 95, MPI  Mostly synchronous  MPI_ALLTOALL on  Np x,y communicators  Some MPI reductions and broadcasts for statistics  Good communications scaling  ACL and MCR  Sibling Linux clusters  ~1000 Intel P4 nodes, dual 2.4 GHz  Up to 1728 CPUs  Fixed workload per CPU  Ported to BlueGene/L

Performance Technology for Productive, High-End Parallel ComputingLACSI Tau Profiling of Miranda on BG/L 128 Nodes512 Nodes1024 Nodes  Miranda team is using TAU to profile code performance  Routinely runs on BG/L for 1000 CPUs for minutes  Scaling studies (problem size, number of processors)

Performance Technology for Productive, High-End Parallel ComputingLACSI Fine Grained Profiling via Tracing  Miranda uses TAU to generate traces  Combines MPI calls with HW counter information  Detailed code behavior to focus optimization efforts

Performance Technology for Productive, High-End Parallel ComputingLACSI Max Heap Memory (KB) used for problem on 16 processors of ASC Frost at LLNL Memory Usage Analysis  BG/L will have limited memory per node (512 MB)  Miranda uses TAU to profile memory usage  Streamlines code  Squeeze larger problems on the machine

Performance Technology for Productive, High-End Parallel ComputingLACSI Kull Performance Optimization (Miller, LLNL)  Kull is a Lagrange hydrodynamics code  Physics packages written in C++ and Fortran  Parallel Python interpreter run-time environment!  Scalar test problem analysis  Serial execution to identify performance factors  Original code profile indicated expensive functions  CCSubzonalEffects member functions  Examination revealed optimization opportunities  Loop merging  Amortizing geometric lookup over more calculations  Apply to CSSubzonalEffects member functions

Performance Technology for Productive, High-End Parallel ComputingLACSI Kull Optimization Optimized Exclusive Profile Original Exclusive Profile  CSSubzonalEffects member functions total time  Reduced from 5.80 seconds to 0.82 seconds  Overall run time reduce from 28.1 to seconds

Performance Technology for Productive, High-End Parallel ComputingLACSI Important Questions for Application Developers  How does performance vary with different compilers?  Is poor performance correlated with certain OS features?  Has a recent change caused unanticipated performance?  How does performance vary with MPI variants?  Why is one application version faster than another?  What is the reason for the observed scaling behavior?  Did two runs exhibit similar performance?  How are performance data related to application events?  Which machines will run my code the fastest and why?  Which benchmarks predict my code performance best?

Performance Technology for Productive, High-End Parallel ComputingLACSI Multi-Level Performance Data Mining  New (just forming) research project  PSU: Karen L. Karavanic  Cornell: Sally A. McKee  UO: Allen D. Malony and Sameer Shende  LLNL: John M. May and Bronis R. de Supinski  Develop performance data mining technology  Scientific applications, benchmarks, other measurements  Systematic analysis for understanding and prediction  Better foundation for evaluation of leadership-class computer systems

Performance Technology for Productive, High-End Parallel ComputingLACSI Goals  Answer questions at multiple levels of interest  Data from low-level measurments and simulations  use to predict application performance  data mining applied to optimize data gathering process  High-level performance data spanning dimensions  Machine, applications, code revisions  Examine broad performance trends  Need technology  Performance data instrumentation and measurement  Performance data management  Performance analysis and results presentation  Automated performance exploration

Performance Technology for Productive, High-End Parallel ComputingLACSI Specific Goals  Design, develop, and populate a performance database  Discover general correlations application performance and features of their external environment  Develop methods to predict application performance on lower-level metrics  Discover performance correlations between a small set of benchmarks and a collection of applications that represent a typical workload for a give system  Performance data mining infrastructure is important for all of these goals  Establish a more rational basis for evaluating the performance of leadership-class computers

Performance Technology for Productive, High-End Parallel ComputingLACSI PerfTrack: Performance DB and Analysis Tool PSU: Kathryn Mohror, Karen Karavanic UO: Kevin Huck, Allen D. Malony LLNL: John May, Brian Miller (CASC)

Performance Technology for Productive, High-End Parallel ComputingLACSI TAU Performance Data Management Framework

Performance Technology for Productive, High-End Parallel ComputingLACSI TAU Performance Regression (PerfRegress)

Performance Technology for Productive, High-End Parallel ComputingLACSI Background – Ahn & Vetter, 2002  “Scalable Analysis Techniques for Microprocessor Performance Counter Metrics,” SC2002  Applied multivariate statistical analysis techniques to large datasets of performance data (PAPI events)  Cluster Analysis and F-Ratio  Agglomerative Hierarchical Method - dendogram identified groupings of master, slave threads in sPPM  K-means clustering and F-ratio - differences between master, slave related to communication and management  Factor Analysis  shows highly correlated metrics fall into peer groups  Combined techniques (recursively) leads to observations of application behavior hard to identify otherwise

Performance Technology for Productive, High-End Parallel ComputingLACSI Thread Similarity Matrix  Apply techniques from the phase analysis (Sherwood)  Threads of execution can be visually compared  Threads with abnormal behavior show up as less similar than other threads  Each thread is represented as a vector (V) of dimension n  n is the number of functions in the application V = [f 1, f 2, …, f n ] (represent event mix)  Each value is the percentage of time spent in that function  normalized from 0.0 to 1.0  Distance calculated between the vectors U and V: ManhattanDistance(U, V) = ∑ |u i - v i | i=0 n

Performance Technology for Productive, High-End Parallel ComputingLACSI sPPM on Blue Horizon (64x4, OpenMP+MPI) TAU profiles 10 events PerfDMF threads 32-47

Performance Technology for Productive, High-End Parallel ComputingLACSI sPPM on MCR (total instructions, 16x2) TAU/PerfDMF 120 events master (even) worker (odd)

Performance Technology for Productive, High-End Parallel ComputingLACSI sPPM on MCR (PAPI_FP_INS, 16x2) TAU profiles PerfDMF master/worker higher/lower

Performance Technology for Productive, High-End Parallel ComputingLACSI sPPM on Frost (PAPI_FP_INS, 256 threads)  View of fewer than half of the threads of execution is possible on the screen at one time  Three groups are obvious:  Lower ranking threads  One unique thread  Higher ranking threads  3% more FP  Finding subtle differences is difficult with this view

Performance Technology for Productive, High-End Parallel ComputingLACSI  Dendrogram shows 5 natural clusters:  Unique thread  High ranking master threads  Low ranking master threads  High ranking worker threads  Low ranking worker threads sPPM on Frost (PAPI_FP_INS, 256 threads) TAU profiles PerfDMF R access threads

Performance Technology for Productive, High-End Parallel ComputingLACSI sPPM on MCR (PAPI_FP_INS, 16x2 threads) masters slaves

Performance Technology for Productive, High-End Parallel ComputingLACSI sPPM on Frost (PAPI_FP_INS, 256 threads)  After k-means clustering into 5 clusters  Similar natural clusters are grouped  Each groups performance characteristics analyzed  256 threads of data has been reduced to 5 clusters! SPPMINTERFDIFUZEDINTERFBarrier [OpenMP:runhyd3.F ]

Performance Technology for Productive, High-End Parallel ComputingLACSI Extreme Performance Scalable Oss (ZeptoOS)  DOE, Office of Science  OS / RTS for Extreme Scale Scientific Computation  Argonne National Lab and University of Oregon  Investigate operating system and run-time (OS/R) functionality required for scalable components used in petascale architectures  Flexible OS/R functionality  Scalable OS/R system calls  Performance tools, monitoring, and metrics  Fault tolerance and resiliency  Approach  Specify OS/R requirements across scalable components  Explore flexible functionality (Linux)  Hierarchical designs optimized with collective OS/R interfaces  Integrated (horizontal, vertical) performance measurement / analysis  Fault scenarios and injection to observe behavior

Performance Technology for Productive, High-End Parallel ComputingLACSI ZeptoOS Plans  Explore Linux functionality for BG/L  Explore efficiency for ultra-small kernels  Scheduler, memory, IO  Construct kernel-level collective operations  Support for dynamic library loading, …  Build Faulty Towers Linux kernel and system for replaying fault scenarios  Extend TAU  Profiling OS suites  Benchmarking collective OS calls  Observing effects of faults

Performance Technology for Productive, High-End Parallel ComputingLACSI Discussion  As high-end systems scale, it will be increasingly important that performance tools be used effectively  Performance observation methods do not necessarily need to change in a fundamental sense  Just need to be controlled and used efficiently  More intelligent performance systems for productive use  Evolve to application-specific performance technology  Deal with scale by “full range” performance exploration  Autonomic and integrated tools  Knowledge-based and knowledge-driven process  Deliver to community next-generation

Performance Technology for Productive, High-End Parallel ComputingLACSI Support Acknowledgements  Department of Energy (DOE)  Office of Science contracts  University of Utah ASCI Level 1 sub-contract  ASC/NNSA Level 3 contract  NSF  High-End Computing Grant  Research Centre Juelich  John von Neumann Institute  Dr. Bernd Mohr  Los Alamos National Laboratory