Eclipse Memory Analyzer
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Eclipse Memory Analyzer

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Eclipse Memory Analyzer Eclipse Memory Analyzer Presentation Transcript

  • Eclipse Memory Analyzer – More Than Just a Heap Walker Andrew Johnson (IBM) Elena Nayashkova (SAP)
  • Introduction
    • Java memory-related problems are very common
    • Many are extremely difficult to analyze
    • Analysis requires expertise in the analyzed source code
    • Eclipse Memory Analyzer:
      • Simplifies memory analysis
      • Extensible
      • Free for download @ www.eclipse.org/mat
  • A Little Bit of History
    • Problem #1: multi-GB heap dumps from 64-bit machines
      • Quickly open and re-open a heap dump on 32-bit machines
    • Problem #2: millions of objects. Where is the „needle“?
      • Dominator Tree: fast calculation of retained memory
      • Meaningful names for class loaders: see components
      • SQL-like language: create custom queries
    • Problem #3: complexity of analysis
      • Reports on memory leak suspects and checks for known antipatterns
    • Problem #4: HPROF heap dumps only
      • Support for IBM system dumps
    View slide
  • Agenda
    • Support for IBM System Dumps
    • Automated Analysis
    • Equinox OSGi Bundle Explorer
    View slide
  • IBM Dumps
    • VM dumps differ between vendors (e.g. IBM and Sun)
    • Diagnostic Tooling Interface for Java (DTFJ) hides differences between dumps from different VMs
    • DTFJ is being standardized via JSR 326
    • Need a VM option to get a system (= process) dump on OutOfMemoryError
    • System dumps are post-processed with JExtract
    • Adapter for MAT available from IBM to read the dumps
    • Adapter uses DTFJ to open the dump & read the object/class data, then passes the data into MAT
    • MAT then displays data just like an HPROF dump
  • Demo
    • DTFJ – adapter
      • Acquire and open an IBM heap dump
      • Run application with dump option java -Xdump:system:events=throw,filter=java/lang/OutOfMemoryError
      • Postprocess dump to add extra VM data jextract <name of dump> .dmp
      • Open the jextract-ed file in Memory Analyzer and analyze as Sun heap dump
  • Demo
    • Memory Leak Hunter
      • Automatically detect memory leak suspects
      • Discover if the issue is known (and a fix available)
      • Collect details for in depth analysis by the code experts
  • Report Overview Any up-to-date architecture loads components with separate class loaders, be it OSGi or JEE application servers. Extensible to display meaningful names. Classification for trouble ticket system: less ping-pong of trouble tickets. Search by keywords: identify if problem is known One big object: memory leak suspect
  • Report Details Accumulated objects A significant drop in the retained sizes shows the accumulation point The chain of objects and references which keep the suspect alive
  • Demo
    • Top Components Report
      • Analyze components, that occupy more memory, than a certain threshold
      • Give hints where memory footprint can be optimized
      • Check for known antipatterns
  • Report Details
  • Report Details
  • Equinox OSGi Bundle Explorer
    • Core runtime of Eclipse uses Equinox OSGi framework. A plug-in is an OSGi bundle.
    • For each bundle present in your Equinox-based application Memory Analyzer’s Bundle Explorer shows:
      • name and version
      • state and location
      • dependencies and dependents
      • services contributed and consumed
      • extension points and extensions
      • hosted bundle fragments
  • Demo
    • Equinox OSGi Bundle
    • Explorer
      • Show the state of all bundles in the analyzed application
      • What other bundles does my bundle depend on at runtime?
      • Detect duplicate bundles
  • What’s Next?
    • Compare multiple heap dumps
    • Acquire heap dumps interactively
    • Become part of Galileo Simultaneous Release
  • Thank You!
    • Memory Analyzer @ Eclipse:
    • www.eclipse.org/mat
    • IBM DTFJ-adapter for Eclipse Memory Analyzer:
    • www.ibm.com/developerworks/java/jdk/tools/mat.html
    • Memory Analyzer Wiki @ SAP:
    • www.sdn.sap.com/irj/sdn/wiki?path =/display/Java/ Java+Memory+Analysis
    • Blogs:
    • dev.eclipse.org/blogs/memoryanalyzer
  • Binary Heap Dump
    • A heap dump is a snapshot of objects that are alive at one point in time.
    • It contains:
            • Objects: fields, references, primitive values, …
            • Classes: class loader, super class, static fields, …
        • A heap dump does not contain
            • where the objects have been created
            • which objects have been garbage collected
    For Your Reference IOIOII IOIIOI OIOIO IIOIIOI IOIOII IOIIOI OIOIO IIOIIOI
  • How to Get a Heap Dump
    • Non-Interactive
      • -XX:+HeapDumpOnOutOfMemoryError
    • On Demand
      • JDK1.4.2_12 and -XX:+HeapDumpOnCtrlBreak
      • JDK6 and Jconsole
    • On IBM VMs -Xdump:system:events=throw,filter=java/lang/OutOfMemoryError, request=exclusive+prepwalk
    • More…
      • http://wiki.eclipse.org/index.php/MemoryAnalyzer#Getting_a_Heap_Dump
    For Your Reference
  • Shallow and Retained Size
    • Shallow heap is the memory consumed by one object
    • Retained set of X is the set of objects that will be garbage collected if X is garbage collected
    • Retained heap of X is the sum of shallow sizes of all objects in the retained set of X , i.e. memory kept alive by X
    For Your Reference Set of elements Retained Set C C, F, G, J K K C, K C, F, G, J, K, I
  • Dominator Tree
    • The Dominator Tree is a Transformation of the Cyclic Object Graph into a “Keep-Alive” Tree:
      • Every node in the Tree is directly responsible for keeping alive its children
      • Object X dominates object Y if all paths from the roots to Y run through X
    For Your Reference
    • Benefits:
    • Fast calculation of the retained size (sum all children)
    • List of distinct big
    • objects (first level of the tree)
    • Fast identification of
    • responsible objects (just go up the tree)