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Eclipse Memory Analyzer - More Than Just a Heap Walker
- 1. Eclipse Memory Analyzer– More Than Just a Heap Walker Andrew Johnson (IBM) Elena Nayashkova (SAP)
- 2. Introduction The numberof memory-related problems is very high They are extremely difficult to analyze Analysis requires expertise in the analyzed code Eclipse Memory Analyzer: Simplifies memory analysis Extensible Free for download @ www.eclipse.org/mat
- 3. A Little Bitof 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
- 4. Agenda Support forIBM System Dumps Automated Analysis Equinox OSGi Bundle Explorer
- 5. IBM Dumps IBMVM dumps differ from Sun VM dumps Need a VM option to get system dump on OutOfMemory System dumps are postprocessed with JExtract Adapter for MAT available from IBM to read these dumps Adapter uses Diagnostic Tooling Interface for Java (DTFJ) to read the dumps, then passes data to MAT DTFJ isolates differences between dumps from different levels of IBM VMs
- 6. 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
- 7. Demo Memory LeakHunter 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
- 8. Report Overview Anyup-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
- 9. Report Details Accumulatedobjects A significant drop in the retained sizes shows the accumulation point The chain of objects and references which keep the suspect alive
- 10. Demo Top ComponentsReport Analyze components, that occupy more memory, than a certain threshold Give hints where memory footprint can be optimized Check for known antipatterns
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- 13. Equinox OSGi BundleExplorer 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
- 14. Demo Equinox OSGiBundle Explorer Show the state of all bundles in the analyzed application What other bundles does my bundle depend on at runtime? Detect duplicate bundles
- 15. What’s Next? Comparemultiple heap dumps Acquire heap dumps interactively Become part of Galileo Simultaneous Release
- 16. Thank You! MemoryAnalyzer @ 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
- 17. Binary Heap DumpA 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
- 18. How to Geta Heap Dump Non-Interactive -XX:+HeapDumpOnOutOfMemoryError On Demand JDK1.4.2_12 and -XX:+HeapDumpOnCtrlBreak JDK6 and Jconsole More… http://wiki.eclipse.org/index.php/MemoryAnalyzer#Getting_a_Heap_Dump For Your Reference
- 19. Shallow and RetainedSize 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
- 20. Dominator Tree TheDominator 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)