Profiling/Tracing Method and Tool Evaluation Strategy Summary Slides Hung-Hsun Su UPC Group, HCS lab 1/25/2005

Profiling/Tracing Method

Experimental performance measurement Instrumentation – insertion of instrumentation code (in general) Measurement – actual measuring stage Analysis – filtering, aggregation, analysis of data gathered Presentation – display of analyzed data to the user. The only phase that deals directly with user Optimization – process of resolving bottleneck

Instrumentation (1) Overhead  Manual – amount of work needed from user  Performance – overhead added by tool to program Profiling / Tracing  Profiling – collecting of statistical event data. Generally refers to filtering and aggregating a subset of event data after program terminates  Tracing – Use to record the majority of events possible in logical order (generally with timestamp). Can use to reconstruct accurate program behavior. Require large amount of storage 2 ways to lower tracing cost – (1) compact tract file format (2) Smart tracing system that turns on and off Manual vs. Automatic – user/tool that is responsible for the instrumentation of original code. Categorization of which event is better suited for which method is desirable

Instrumentation (2) Number of passes – The number of times a program need to be executed to get performance data. One pass is desirable for long running program but multi-pass can provide more accurate data (ex: first pass=profiling, later pass=tracing using profiling data to turn on and off tracing). Hybrid method is available but might not be as accurate as multi-pass Levels - need at least source and binary to be useful (some event more suited for source level and other binary level)  Source level – manual, pre-compiler, instrumentation language  System level – library or compiler  Operating system level  Binary level – statically or dynamically

Tool Evaluation Strategy

Feature (section)DescriptionInformation to gatherCategoriesImportance Rating Available metrics ( )Kind of metric/events the tool can tract (ex: function, hardware, synchronization) Metrics it can provide (function, hw …) ProductivityCritical Cost (9.1.1)Physical cost for obtaining software, license, etc. How muchMiscellaneousAverage Documentation quality (9.3.2) Helpfulness of the document in term of understanding the tool design and its usage (usage more important) Clear document? Helpful document?MiscellaneousMinor Extendibility (9.3.1)Ease of (1) add new metrics (2) extend to new language, particularly UPC/SHMEM 1.Estimating of how easy it is to extend to UPC/SHMEM 2.How easy is it to add new metrics MiscellaneousCritical Filtering and aggregation ( ) Filtering is the elimination of “noise” data, aggregation is the combining of data into a single meaningful event. Does it provide filtering? Aggregation? To what degree Productivity, Scalabilit y Critical Hardware support (9.1.4)Hardware support of the toolWhich platforms?Usability, Portabilit y Critical Heterogeneity support (9.1.5)Heterogeneity deals with the ability to run the tool in a system where nodes have different HW/SW configuration. Support running in a heterogeneous environment? MiscellaneousMinor

Installation (9.1.2)Ease of installing the tool1.How to get the software 2.How hard to install the software 3.Components needed 4.Estimate number of hours needed for installation UsabilityMinor Interoperability ( )Ease of viewing result of tool using other tool, using other tool in conjunction with this tool, etc. List of other tools that can be used with this PortabilityAverage Learning curve (9.1.6)Learning time required to use the tool Estimate learning time for basic set of features and complete set of features Usability, Productiv ity Critical Manual overhead ( )Amount of work needed by the user to instrument their program 1.Method for manual instrumentation (source code, instrumentation language, etc) 2.Automatic instrumentation support Usability, Productiv ity Average Measurement accuracy ( ) Accuracy level of the measurementEvaluation of the measuring methodProductivity, Portabilit y Critical Multiple analyses ( )The amount of post measurement analysis the tool provides. Generally good to have different analyses for the same set of data Provide multiple analyses? Useful analyses? UsabilityAverage Multiple executions (9.3.5)Tool support for executing multiple program at once Support multiple executions?ProductivityMinor  Aver age Multiple views ( )Tool’s ability to provide different view/presentation for the same set of data Provide multiple views? Intuitive views? Usability, Productiv ity Critical

Performance bottleneck identification ( ) Tool’s ability to identify the point of performance bottleneck and it’s ability to help resolving the problem Support automatic bottleneck identification? How? ProductivityMinor  Aver age Profiling / tracing support ( ) Method of profiling/tracing the tool utilize 1.Profiling? Tracing? 2.Trace format 3.Trace strategy 4.Mechanism for turning on and off tracing Productivity, Portabilit y, Scalabilit y Critical Response time (9.2.6)Amount of time needed before any useful information is feed back to the user after program execution How long does it take to get back useful information ProductivityAverage Searching (9.3.6)Tool support for search of particular event or set of events Support data searching?ProductivityMinor Software support (9.1.3)Software support of the tool1.Libraries it supports 2.Languages it supports Usability, Productiv ity Critical Source code correlation ( ) Tool’s ability to correlate event data back to the source code Able to correlate performance data to source code? Usability, Productiv ity Critical System stability (9.3.3)Stability of the toolCrash rateUsability, Productiv ity Average Technical support (9.3.4)Responsiveness of the tool developer 1.Time to get a response from developer. 2.Quality/usefulness of system messages UsabilityMinor  Aver age