Vladimir PavlovDimitar GiormovSAP Labs Bulgaria

Using and Extending Memory Analyzer into Uncharted Waters

Memory Analyzer

AGENDA

Introduction The Headaches Eclipse Memory Analyzer

Extending Eclipse Memory Analyzer API and Extension Points JRuby Case Android Apps Case

Q & A

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Memory leaks Hard to debug and find the root cause Eventually lead to OOM errors

Brings your system down Often not reproducible

Thread issues Deadlocks Exhausted threads Waiting for an external resource – e.g. DB connection

Application does not respond Whole system hangs

THE HEADACHES

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Eclipse Memory Analyzer (MAT) is… Java heap analyzer Helps find memory leaks and reduce memory consumption UI and programmatic access to data in the heap dumps Multi-Gigabyte Java Heap Dumps Are Nothing to Fear Now Soooo much faster than other tools, e.g. jhat Very little memory “overhead” for processing heap dumps (again – cf. jhat) Supports Sun, SAP, HP, IBM JDKs 1.4.2 and above Automatic problem recognition Could also process thread dumps and correlate data to provide additional details Initial contribution from SAP, joined by IBM Highly extensible

ECLIPSE MEMORY ANALYZER

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Memory Analyzer

Why extend MAT? To save time doing the same thing repeatedly To help others use the same technique as you To do things not possible from the GUI To build in application or domain specific logic

How to extend MAT? MAT provides a set of Eclipse extension points User writes an extension plug-in MAT provides an API for reading data from a heap dump

EXTENDING MAT

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Isnapshot Represents a heap dump Methods for reading classes and objects, getting sizes, GC roots, referenced objects,

etc. Object model

IClass IObject

IInstance– IClassLoader

IArray– IPrimitiveArray– IObjectArray

PROGRAMMATIC ACCESS TO A SNAPSHOT

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Name Resolver Used to give meaningful descriptions of objects Similar to a toString() method Extension point: org.eclipse.mat.api.nameResolver

Query Used for exploring dumps or detailed analysis Result in the form of a table, tree, histogram, pie chart, free text... Integrated into MAT’s menus “Collaboration” of queries Extension point: org.eclipse.mat.report.query

Request Resolver Used to provide details about what a thread was doing Contributes to Leak Suspects report Extension point: org.eclipse.mat.api.requestResolver

EXTENSION POINTS

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Parser – for new heap dump types and VMs, such as for Jikes RVM Trigger Heap Dump – org.eclipse.mat.api.heapDumpProvider

For new VM types Reports – org.eclipse.mat.report.report

HTML results of queries – also used for batch mode Thread Resolver – additional thread data such as native stacks Ticket Resolver – can identify appropriate routing for problems

Based on classes and class loaders of problematic objects Rendering – org.eclipse.mat.api.renderer

Additional to HTML and CSV

Annotations used as filters and for configuration

EXTENSION POINTS (CONTD.)

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Ruby is… Dynamic scripting language Object-oriented Focus on simplicity and productivity Elegant syntax, natural to read and easy to write

JRuby is… 100% Java implementation of the Ruby programming language Interpreter running atop the JVM Generating Java bytecode (JIT compilation mode) Tight integration with Java

RUBY AND JRUBY

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Adding JRuby into the picture…

THE HEADACHES – AGGRAVATED

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What were the goals Identify memory leaks (critical when talking about embedded systems due to

hardware restrictions) Filter memory usage by classes belonging to the users’ application Simpler workflow: developers start analyzing by classes they already know (not

Android system classes)

Why MAT was chosen The MAT perspective provides views to analyze application status, identify leaks,

and so on, given an HPROF file Reports are easy to navigate and provide information about retained heap It is Eclipse based Android supports the creation and extraction of HPROF files

MAT INTEGRATION WITH MOTODEV STUDIO

Implemented an Extension Extension point used: org.eclipse.mat.ui Added a new page extending CompositeHeapEditorPane

Created MotodevPane based on OQLPane class

WORK DONE ON MAT

The integration of MOTODEV Studio, Google DDMS and Eclipse MAT worked very well.

Used the org.eclipse.mat.ui extension point, which was well-documented.

It took about 2 weeks of one developer to study the project, implement and test the solution.

OVERALL EXPERIENCE

Eclipse Memory Analyzer provides:

Powerful and efficient memory analysis features out-of-the-box

API for extracting data from a heap dump

Application or domain specific analysis can be added as extensions

SUMMARY

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RESOURCES

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Memory Analyzer

THANK YOU!

in: vpavlovt: @giormov