News from ACTC Present and Future of the IBM High ...

© 2002 IBM CorporationJune 2005

News from ACTC

Present and Future of the IBM High Performance Computing Toolkit

Simone SbaragliaAdvanced Computing TechnologyIBM T.J. Watson Research Center

Advanced Computing Technology Center

The IBM High Performance Computing Toolkit © 2005 IBM Corporation

• IBM goal: • A common application performance analysis environment across all

IBM HPC servers

• Common framework for performance analysis of communication, memory, CPU, shared-memory, I/O

• Operate on the binary and yet provide reports in terms of source-level symbols

• Full source code traceback capability

• Dynamically activate/deactivate data collection and change what information to collect

• Where we are:• One consolidated package (AIX)

• Tools for MPI, OMP, processor, memory etc

• One common visualization GUI


The IBM High Performance Computing Toolkit © 2005 IBM Corporation3

IBM HPC Toolkit Software Components

• Hardware (CPU) PerformanceXprofilerHPM Toolkit

- hpmcount- libhpm- hpmstat

• Shared Memory PerformanceDpomp, PompProf

• Optimized Linear AlgebraWSMP

• Message-Passing PerformanceMP_Profiler, MP_Tracer

• Memory Performance Sigma

• Performance VisualizationPeekPerf

• I/O Performance MIO (modular I/O)



AGENDA

• Xprofiler: call-graph profiling

• HPM: hardware counter data

• MP-Profiler/Tracer: MPI profiling

• PompProf: OpenMP profiling

• SIGMA: memory profiling

• The New HPC Toolkit

• Questions/Comments



Xprofiler

• Compile with -g -pg

• Width of a bar:time includingcalled routines

• Height of a bar:time excludingcalled routines

• Call arrowslabeled withnumber of calls

• Overview windowfor easy navigation(View Overview)



Xprofiler: Zoom In



Xprofiler:

• Xprofiler provides usual gprof reports plus some extra

Flat Profile

Call Graph Profile

Function Index

Function Call Summary

Library Statistics

Source Code with Line Profile (in ticks)

Disassembled Code



HPM: What Are Performance Counters• Extra logic inserted in the processor to count specific events

• Updated at every cycle

• Strengths:Non-intrusive

Accurate

Low overhead

• Weaknesses:Specific for each processor

Access is not well documented

Lack of standard and documentation on what is counted



HPM: Hardware Counters Examples

• Cycles• Instructions• Floating point instructions• Integer instructions• Load/stores• Cache misses• TLB misses• Branch taken / not taken• Branch mispredictions

• Useful derived metrics

IPC - instructions per cycleFloat point rate (Mflip/s)Computation intensityInstructions per load/storeLoad/stores per cache missCache hit rateLoads per load missStores per store missLoads per TLB missBranches mispredicted %



HPM Toolkit

hpmcountStarts a program and at the end of the execution provides a summary

with hardware counters information and derived metricsSimple to use, no source code modification

libhpmInstrumentation library for performance measurement of Fortran, C,

and C++ applications

hpmstatHardware monitoring at system level



HPMCOUNT Output - Group 5PM_DATA_FROM_L3 (Data loaded from L3) : 64164220PM_DATA_FROM_MEM (Data loaded from memory) : 5623627PM_DATA_FROM_L35 (Data loaded from L3.5) : 281896PM_DATA_FROM_L2 (Data loaded from L2) : 947542929PM_DATA_FROM_L25_SHR (Data loaded from L2.5 shared) : 739PM_DATA_FROM_L275_SHR (Data loaded from L2.75 shared) : 567PM_DATA_FROM_L275_MOD (Data loaded from L2.75 modified) : 903PM_DATA_FROM_L25_MOD (Data loaded from L2.5 modified) : 120

Memory traffic : 2879.297 MBytesMemory bandwidth : 96.317 MBytes/secEstimated latency from loads from memory : 1.730 secTotal loads from L3 : 64.446 ML3 traffic : 8249.103 MBytesL3 bandwidth : 275.945 MBytes/secEstimated latency from loads from L3 : 5.067 secL3 Load miss rate : 8.026 %Total loads from L2 : 947.545 ML2 traffic : 121285.793 MBytesL2 bandwidth : 4057.200 MBytes/secEstimated latency from loads from L2 : 8.747 secL2 Load miss rate : 6.886 %

Estimation based on user input



LIBHPMAllows to go in the source code and instrument different sections independently

• Declaration:#include f_hpm.h

• Use:call f_hpminit( 0, “prog” )call f_hpmstart( 1, “work” )do call do_work()call f_hpmstart( 22, “more work” )

call compute_meaning_of_life()call f_hpmstop( 22 )

end docall f_hpmstop( 1 )call f_hpmterminate( 0 )

• Supports MPI, OpenMP, Pthreads

• Multiple instrumentation points

• Nested sections

• Supports Fortran, C, C++



PeekPerf: Unified GUI with Source Code Traceback

HPM MP_profiler/Tracer PomProf SiGMA MIO

(work in progress)

PeekPerf

Available on AIX, Linux, Windows, Mac OS, BG/L, …



HPM Visualization Using PeekPerf



Message-Passing PerformanceMP_Profiler/MP_Tracer

– Implements wrappers around MPI calls using the PMPI interfacestart timercall pmpi equivalent functionstop timer

– Captures both “summary” and trace data for MPI calls with source code traceback

– No changes to source code, but MUST compile with -g– ~1.7 microsecond overhead per MPI call– Does not synchronize MPI calls– Compile with –g and link with libmpitrace.a– Generate XML files for peekperf



MP_Profiler Visualization Using PeekPerf



MP_Tracer Visualization Using PeekPerf



OMP Profiler (PompProf)

• POMP proposal motivated by the MPI profiling interface (PMPI)

• PompProf is a profiler for OpenMP applications implemented on top of DPCL, using the POMP specification

• Generates a detailed profile describing overheads and time spentby 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 bevisualized with PeekPerf



PompProfiler and PeekPerf



SIGMA Infrastructure

Infrastructure for symbolic, dynamic, performance-oriented binary instrumentation

– Inject arbitrary user-supplied probes into a binary application

Provides a platform to:

– Develop performance tools– Experiment with memory performance models– Ask “what-if” questions regarding data and code rearrangements– Provide feedback on design of new memory architectures– Identify performance bottlenecks due to the memory hierarchy and

data layout

SIGMA Memory Profiler is integrated in the HPC Toolkit



duringexecution

memorysimulation

instrumentedprogramexecution

instrumented binary

events

instrumented binary

SigmaSoftware

catalogueof events

library ofevent-

handlers

psigmaInst

script of desired events,handlers and machine

configurationapplication

binaryuser

event-handler

user

activate/deactivate

userevent-handler

Sigmaevent-handler

standardized event description interface



Memory Profile:

– Execute functional cache simulation and provide memory profile– Power3/Power4 architectures prefetching implemented– Write-Back/Write-Through caches, replacement policies etc

Provide counters such as hits, misses, cold misses foreach cache leveleach functioneach data structureeach data structure within each function

Output sorted by the SIGMA memtime:SUM( LoadHits(i)*LoadLat(i) + StoreHits(i)*StoreLat(i) ) +

#TLBmisses * Lat(TLBmiss)

memtime should track wall time for memory bound applications



L1 L2 L3 TLB MEM FUNCTION: calc1 (memtime = 0.0050)

Load Acc/Miss/Cold 522819/2252/1 2252/345/0 345/0/0 784419/126/0 0/-/-Load Acc/Miss Ratio 232 6 - 6225 -Load Hit Ratio 99.57% 84.68% 100.00% 99.98% -Est. Load Latency 0.0008 sec 0.0000 sec 0.0000 sec 0.0001 sec 0.0000 sec Load Traffic - 238.38 Kb 43.12 Kb - 0.00 Kb ………

FUNCTION: calc2 (memtime = 0.0042)

Load Acc/Miss/Cold 622230/2631/0 2631/1661/0 1661/0/0 814269/94/0 0/-/-Load Acc/Miss Ratio 236 1 - 8662 -Load Hit Ratio 99.58% 36.87% 100.00% 99.99% -Est. Load Latency 0.0010 sec 0.0000 sec 0.0001 sec 0.0001 sec 0.0000 sec Load Traffic - 121.25 Kb 207.62 Kb - 0.00 Kb ………

L1 L2 L3 TLB MEM DATA: u (memtime = 0.0012)

Load Acc/Miss/Cold 167710/708/0 708/317/0 317/0/0 216097/31/0 0/-/-Load Acc/Miss Ratio 236 2 - 6970 -Load Hit Ratio 99.58% 55.23% 100.00% 99.99% -Est. Load Latency 0.0003 sec 0.0000 sec 0.0000 sec 0.0000 sec 0.0000 sec Load Traffic - 48.88 Kb 39.62 Kb - 0.00 Kb ……….

DATA: v (memtime = 0.0012)

Load Acc/Miss/Cold 167710/721/0 721/316/0 316/0/0 216097/31/0 0/-/-Load Acc/Miss Ratio 232 2 - 6970 -Load Hit Ratio 99.57% 56.17% 100.00% 99.99% -Est. Load Latency 0.0003 sec 0.0000 sec 0.0000 sec 0.0000 sec 0.0000 sec Load Traffic - 50.62 Kb 39.50 Kb - 0.00 Kb ……….

Memory Profile Output



Memory Profile Viewer – Data Structure Focus



The New HPC Toolkit (4Q2005)



New HPC Toolkit

• Common framework for CPU, MPI, OpenMP, Memory, I/O

• Instrumentation at the binary level

• Centralized GUI for instrumentation and analysis

• Dynamic instrumentation capabilities

• Enhanced with graphics capabilities (bar charts, plots etc)

• Simultaneous instrumentation for all tools (one run!)

• Query capabilities: compute derived metrics and plot them

• Selective instrumentation of MPI functions



IBM HPC Toolkit Availability

• IBM pSeries ServersLinux on Power

AIX on Power

• All IBM Blue Gene systemsIncluded as part of the system software stack

Customers do not need to acquire additional licensing

• IBM Cell ServerWork in Progress



Support Matrix

HPMCount&

HPMlib

MP-profiler&MP-tracer Xprofiler

SHMEM &

SHMEM-profiler

MIO PompPofiler

SiGMA PeekPerfWatson Sparse Matrix Package

AIX Power

today AIX

5L 5.1, 5.3

today AIX

4.3.3 +

today AIX

5L 5.1

today AIX

5L 5.1

todayAIX

5L 5.1

today AIX

5L 5.1

today AIX

4.3.3+

TodayAIX

4.3.3+

today AIX

5L 5.1

Linux Power

Aug/05 Linux

2.4 &2.6

May/05 Linux

2.6

Aug-Sep/05 Linux

2.6N/A

TBT Linux

2.6N/A

Aug-Sep/05 Linux

2.6TBT

TBTLinux

2.6

Linux JS20

Aug/05 Linux

2.4 &2.6

May/05 Linux

2.6

Aug-Sep/05 Linux

2.6N/A

TBT Linux

2.6 N/A

Aug-Sep/05 Linux

2.6TBT

TBTLinux

2.6

Linux BG/L Aug/05 today today N/A TBT N/A N/A today N/A



Summary• The IBM HPC Toolkit is the IBM environment for HPC application

performance analysis• Three years of field testing and experience

• Visual source code traceback for all metrics

• Common framework for simultaneous performance analysis of CPU, MPI, OpenMP, Memory and I/O

• Available across IBM HPC servers (pSeries, Linux, Blue Gene)

• Future infrastructure characteristics• Instrumentation of the binary

• Common instrumentation and analysis GUI

• Dynamic instrumentation capabilities

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