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How to analyse heap dump

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                              How to analyse heap dump

I have already discussed about heap dump in one of the post.

Please refer the link below to read it:

http://professionalcurve.blogspot.com/2014/03/heap-dump-how-to-generate-heap-dump.html


Now we will see about how to analyze them. There are various tools for reading heap dump. I prefer MAT (Eclipse Memory Analyzer Tool). It is powerful and free tool which can read, parse and analyze them.

Before opening heap dump in MAT, let’s focus on some basic things related to it:

-         Shallow Size: The sum of the sizes of all contained primitive data types, as well as the size of the references to other objects

-         Retained Heap : The total size of all objects being kept alive by this dominator

What MAT will do with heap dump? It will parse the heap dump and it will appear as below in tree format:

  • char[]
  • java.lang.Object[]
  • java.lang.Class
  • java.lang.String
  • byte[]
  • java.util.HashMap
  • java.util.HashMap$Entry
  • short[]
  • int[]
  • java.util.ArrayList
  • java.lang.Integer


 Then it will calculate retained Heap of objects and display a pie graph which will show which objects as biggest size in term of Retained Heap. Now to find structure or creation of these objects, we need to look into incoming reference (reference to keep objects alive and prevent them to into garbage collector) and outgoing reference (reference which shows actual contents of the instances) of these objects.

To get them, choose List Objects with incoming References from the context menu. It will display tree structure of incoming reference. These references give us idea about objects which are high of retained heap memory.


MAT also allows comparing two heap dump snapshots and finding growing structures and instance counts of two well timed dumps (some amount of load they should be minutes apart, with few load hours or days.).

This way we can find memory leak issues and related objects too.

You can also refer the below link for MAT Knowledge:

http://docwiki.cisco.com/wiki/How_to_analyze_heap_dumps

Comments

  1. GST Refunds Delhi11 April 2018 at 17:48

    very informative post for me as I am always looking for new content that can help me and my knowledge grow better.

    ReplyDelete

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