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Memory Leak Profiling with NetBeans and HotSpot

Clarence J M Tauro

Senior Curriculum Developer, Oracle ST Java Curriculum

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Session Agenda

• About the Speaker

• Different aspects of Performance

• Memory leaks and profiling

• Demo

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About the Speaker

• Clarence J M Tauro – clarence.tauro@oracle.com

• 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

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Different Aspects of Performance

Performance Aspects

Memory footprint

Scalability

Responsiveness

Throughput

In this talk we will look at memory profiling

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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

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Garbage Collection – An Overview

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Garbage Collection – An Overview

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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.

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DEMO – A Servlet with a JavaScript Error

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DEMO – Main Class

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DEMO – NetBeans Profiler Configuration

I am interested in Garbage collection

statistics too

Choosing this option has a lot of additional

overhead

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DEMO – Telemetry Overview

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DEMO – Live Profiling Results

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DEMO – Snapshot of String Class

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DEMO – Stack Trace

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DEMO – Source of handleScriptException

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DEMO – Find Usaged on _errorMessages

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DEMO – Source of ____________JavaScript.clearErrorMessages()

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DEMO – Find Usages on -------------------------------------------------------------JavaScript.clearErrorMessages()

So, who calls the JavaScriptEngineFactory.clearErrorMessages()??

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So, who calls the HttpUnitOptions.clearScriptErrorMessages()??

DEMO – Find Usages on JavaScriptEngineFactory.clearErrorMessages(

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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.

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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

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• 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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