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Memory Leak Profiling with NetBeans and HotSpot Clarence J M Tauro Senior Curriculum Developer, Oracle ST Java Curriculum 

3 Session Agenda • About the Speaker • Different aspects of Performance • Memory leaks and profiling • Demo 

4 About the Speaker • Clarence J M Tauro – [email protected] • Senior Curriculum Developer, Java Curriculum (Oracle ST Curriculum) • ~7 Years Professional Teaching and Instructional Design Experience • Masters of Science in Information Technology • Masters of Technology in Computer Science • Masters of Philosophy in Computer Science • Doctor of Philosophy in Computer Science [expected to graduate by August 2012] • Guest faculty to various Colleges and Universities 

5 Different Aspects of Performance Performance Aspects Memory footprint Scalability Responsiveness Throughput In this talk we will look at memory profiling 

6 Memory Leak Profiling: Why and When • Memory leaks are situations where a reference to allocated objects remains unintentionally reachable and as a result cannot be garbage collected. – Leads to poor application performance – Can lead to application failure – Can be hard to diagnose 

7 Garbage Collection – An Overview 

8 Garbage Collection – An Overview 

9 Profiling • An act of collecting or observing performance data from an operating or running application. • Usually more intrusive than monitoring. • Usually a narrower focus than monitoring. 

10 DEMO – A Servlet with a JavaScript Error 

11 DEMO – Main Class 

12 DEMO – NetBeans Profiler Configuration I am interested in Garbage collection statistics too Choosing this option has a lot of additional overhead 

13 DEMO – Telemetry Overview 

14 DEMO – Live Profiling Results 

15 DEMO – Snapshot of String Class 

16 DEMO – Stack Trace 

17 DEMO – Source of handleScriptException 

18 DEMO – Find Usaged on _errorMessages 

19 DEMO – Source of ____________JavaScript.clearErrorMessages() 

20 DEMO – Find Usages on ----------------------------------------- --------------------JavaScript.clearErrorMessages() So, who calls the JavaScriptEngineFactory.clearErrorMessages()?? 

21 So, who calls the HttpUnitOptions.clearScriptErrorMessages()?? DEMO – Find Usages on JavaScriptEngineFactory.clearErrorMessages( ) 

22 DEMO – Find Usages on HttpUnitOptions.clearScriptErrorMessages() Ahh.. Haa.. You just found the root cause of the memory leak. The _errorMessages ArrayList is NEVER cleared.. It has only elements added to it. 

23 Farewell to the memory leak! So, to fix this memory leak, the ArrayList needs to be explicitly cleared. This is a task for the authors of HttpUnit 

24 • Java Performance Tuning and Optimization Course from Oracle University • Java Performance - Charlie Hunt (Author), Binu John (Author) (Expected August 2011) Where to go? 

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