SvPablo Evaluation Report Hans Sherburne, Adam Leko UPC Group HCS Research Laboratory University of Florida Color encoding key: Blue: Information Red: Negative note Green: Positive note

2 Basic Information Name: SvPablo Developer: University of Illinois Current versions:  SvPablo 6.0  SDDF component 5.5  Trace Library component Website: Contact:  ? address on website/documentation are no good

3 Introduction SvPablo  Part of Pablo Project at UIUC Last website update: June, 2004 Website now hosted at Project appears to be inactive at this point  GUI for source code correlation of performance data Instrumentation of source code  Automatic  Interactive Display of performance data  Color coded indicators beside procedure listings and source code  Popup dialogs display more detailed information  Scalability graph

4 Instrumentation/Visualization Process In SvPablo Figure 2: instrumentation/visualization process in SvPablo (c/o [1])

5 Performance Data in SvPablo What can be instrumented?  Function calls  Outer Loops What type of performance data is avalable?  Procedure Statistics Statistics describing all instrumented calls to a procedure  Call Statistics Statistics describing a specific procedure callsite  Loop Statistics Statistics describing an outer loop Statistics provided  Exclusive and inclusive duration  Count  Max, min, mean, std dev.  HW Counters (if available) Scalability  Run program with same instrumentation configuration using varying number of nodes  SvPablo will calculate and graph parallel efficiency for each instrumented procedure and loop

6 Main Window in SvPablo Figure 1: Main window in SvPablo

7 Self-Defining Data Format Self-Defining Data Format (SDDF)is the format used to store performance data in SvPablo  Provides a flexible structure Allows multi-language analysis support Possible to add new metrics easily  Performance File Entries Configuration records  Specifies GUI display information for event, and procedure statistics Event statistics records  In SvPablo events are routine calls, loops, or hardware counter values  Define records, and give value for routine callsites, and loops Procedure statistics records  Define records, and give value for procedures Event locality records  Links events and procedures

8 Data Capture Library Offers a set of functions which can be used to instrument code  Start/End Data Capture  Function Entry/Exit  Loop Start/End  OpenMP applications Threaded Function Entry/Exit Threaded Loop Entry/Exit

9 Errors Abound in SvPablo Parser  Does not understand c++ style comments  Variables not declared at top of function  Once a source file is loaded that cannot be parsed by SvPablo, the application must be restarted to view correlated data for any source code! GUI  Some lines in camel appear instrumentable, but are not Instrumenting these lines causes runtime errors  Routines correctly correlated in Main window, not correctly correlated in “Procedure Statistics” window Compiling Instrumented code  Problems with “void” return types in some code  Some instrumented source code output by SvPablo could not be compiled Executing instrumented code  Errors are generated for functions ending with “exit(0)” Scalability graph  Have to change screen resolution to see entire graph

10 SvPablo – Overhead All programs executed correctly when instrumented Benchmarks marked with a star had high variability in execution time  Readings with stars probably not accurate Instrumenting a large number of loops creates high overhead!

11 Evaluation (1) Available metrics: 2/5  Can use PAPI and MIPS R10000 hardware counters (not evaluated)  Other statistics based on loop and function call count and duration are provided  No statistics regarding communication are provided Cost: 5/5  SvPablo is freely available Documentation quality: 3/5  Documentation covers all available features, however figure placement and arduous terminology impede quick understanding  Documentation does describe how one might extend the tool Extendibility: 3/5  SvPablo source code is freely available  May be more of a hassle than helpful due to large number of bugs  Project appears to be inactive, so we’d likely be on our own for support Filtering and aggregation: 3/5  Only hardware counter values and statistical data are recorded,

12 Evaluation (2) Hardware support: 4/5  Sun Solaris, SGI IRIX, IBM SP, Compaq Alpha, NEC SX6 Linux workstations Heterogeneity support: 0/5 (not supported) Installation: 3.5/5  Installation on Linux platform required a number of manual configurations, but was not bad overall Interoperability: 3/5  SvPablo uses SDDF file format  The source code for the SDDF component is freely available, and documented  A SDDF to XML conversion component is also freely available Learning curve: 3.5/5  The interface is fairly intuitive, but takes some use to get comfortable  The terminology and project file hierarchy are a bit cumbersome Manual overhead: 3/5  It is fairly straightforward to instrument all loops and routines  It is necessary to manually select only important loops in order to keep overhead low Measurement accuracy: 3/5  Tracing all loops increased overhead substantially in Camel

13 Evaluation (3) Multiple analyses: 1/5  Scalability analysis view is only means of analysis provided Multiple executions: 3.5/5  SvPablo includes a view to select performance data from multiple runs and view a graph plotting efficiency for each instrumented routine Multiple views: 2/5  A limited number of views are available  Only profile data (not trace data) is viewable Performance bottleneck identification: 2.5/5  Scalability view shows methods with poor parallel efficiency  Routines can be sorted based on max exclusive duration Profiling/tracing support: 1.5/5  Only profiling is supported  Profiling is done on routine, and loop execution metrics  Communication profiling is not available

14 Evaluation (4) Response time: 2/5  Data is not available in SvPablo until after execution completes and performance data is processed Software support: 3/5  MPI profiling library allows linking against different MPI implementations  C and Fortran are fully supported, PGI HPF is partially supported (no selective instrumentation) Source code correlation: 4/5  Source code correlation of profile data is the main view offered System stability: 2.5/5  SvPablo is very finicky about C syntax (once source code is loaded with syntax that cannot be understood, program must be restarted!)  On occasion SvPablo seg faults for unknown reasons Technical support: 0/5  addresses listed in documentation and on webpage are bad

15 Bottleneck Identification: Performance Tool Test Suite: CAMEL, LU Testing metric: what did profile data tell us? CAMEL: FAIL  Not possible to profile a section of code that is not a loop or function call  Not possible to represent actual dynamic behavior (no trace)  Required a lot of effort to clean up syntax Can’t have:  C++ “//” style comments  Variable initialization after beginning of function NAS LU: NOT TESTED  Unable to succesfully instrument code Segmenation fault, when opening init_comm.f Instrumenting lu.f alone causes execution errors

16 Bottleneck Identification: Performance Tool Test Suite: PPerfMark Big message: PASSED  Profile showed large amount of time spent in Send and Receive Diffuse procedure: PASSED  Profile showed large amount of time spent in bottleneck procedure, even though time is diffused across processes Hot procedure: PASSED  Profile showed large amount of time spent in bottleneck procedure Intensive server: TOSS-UP  Profile showed large amount of time spent in Recieve, and in waste_time()  It would take a lot of reasoning to figure out the two are related Ping pong: TOSS-UP  Profile indicates lots of time spent in Receive, and in Send  Does not show communication pattern between two processes Random barrier: TOSS-UP  Profile shows lots of time spent in Barrier, and waste_time()  Profile does not show communication pattern amongst processes Small messages: TOSS-UP  Profile shows lots of time spent in Send and Receive  Very high standard deviation, difference between Max/Min  Profile does not show communication pattern amongst processes System time: TOSS-UP  Profile show lots of time spent in kill(), and getpid()  No distinction is made between user and system calls Wrong way: TOSS-UP  Profile show lots of time spent in Send and Receive  Profile does not show communication pattern amongst processes

17 Conclusions The use of a GUI for interactive code instrumentation simplifies the process for the user The source code is available, and fairly well documented Extension of this tool is a possibility  Risky due to no support  Lots of errors experienced!

18 References 1. SvPablo User’s Guide  ftp://