Eclipse Memory Utilisation

On my PC, Eclipse is currently hogging 518 MB of RAM! Want to find out why Eclipse is using up so much memory? This is how:

• Find the process id of Eclipse. You can use the jps command to help.
• Now dump out the java object heap using the jmap command. For example: jmap -dump:format=b,file=C:\temp\eclipse_heap.bin 3080
• Open the heap file (C:\temp\eclipse_heap.bin) in Eclipse.

Eclipse will take a couple of minutes to load the object heap into its Memory Analyser. It will then provide lots of useful information such as:

• A Leak Suspects Report: My main suspect was org.maven.ide.components.nexus_indexer occupying 24,201,456 (24.29%) bytes.
• A Histogram which lists the number of instances per class. There were 583,760 char[] objects and 439,572 String objects on my heap.
• Dominator Tree which lists the biggest objects and what they keep alive. Mine were:
  • org.eclipse.osgi.internal.baseadaptor.DefaultClassLoader @ 0x3f46368 org.maven.ide.components.nexus_indexer (23.1 MB)
  • org.eclipse.jdt.internal.core.JavaModelManager @ 0x4710728 (15.2 MB)
  • org.eclipse.jdt.internal.core.search.indexing.IndexManager @ 0x475c3e8 (9.7 MB)
  • org.eclipse.jdt.internal.ui.text.spelling.SpellCheckEngine @ 0x3d617a8 (6.5 MB)
• Top Consumers which lists the most expensive objects grouped by class and package.

As a result of my findings, I have now removed the Maven Plugin and have also disabled the Spell Checker. Memory is down to 356 MB and the biggest object is org.eclipse.equinox.internal.p2.metadata.repository.MetadataRepositoryManager (26.1 MB).

Further Reading:
Eclipse Memory Analyzer, 10 useful tips/articles