Eclipse Memory Analyzer Tool (MAT)

Eclipse memory analyzer is a java heap analyzer that helps to find memory leaks and reduce memory consumption.

Install MAT Analyzer

We need to install two eclipse plugins:

    1. BIRT Chart Engine: For Getting Memory Information with Pie Chart diagrams

    2. MAT: For Getting Memory Information

1. Install BIRT Chart Engine plugins

    Eclipse —> Help Menu —> Install New Software —> Add

    Enter below information

    Name: BIRT Chart Engine.

    Location: http://download.eclipse.org/birt/update-site/4.3

    Now select only Birt Chart Engine and Go for Install.

2. Install MAT plugins

    Eclipse —> Help Menu —> Install New Software —> Add

    Enter below information

    Name: MAT

    Location: http://download.eclipse.org/mat/1.3/update-site/

Generate Dump file for MAT Analysis

I had written simple java program, which requires lot of heap to initialize, and finally results in “OutOfMemoryError”.

public class HeapError {
 public static void main(String args[]){
  HeapError obj[] = new HeapError[100000000];
    
    for(int i=0; i<100000000; i++)
     obj[i] = new HeapError();
     
    System.out.println("I am done");
 }
}

We need to do some setting to generate heap dump for this application.

Step 1: Right click on program and open “Run configurations”.

Step 2: Go to arguments tab and add 

“-XX:+HeapDumpOnOutOfMemoryError” as VM argument. And run the application.

Step 3: After running application, you can see below messages in console.

java.lang.OutOfMemoryError: Java heap space
Dumping heap to java_pid912.hprof ...
Heap dump file created [3482503 bytes in 0.383 secs]
Exception in thread "main" java.lang.OutOfMemoryError: Java heap space
 at mat_demo.HeapError.main(HeapError.java:5)

Message in console clearly stating that dump is generated to file “java_pid912.hprof”.

Step 4: Dump file is located in project folder itself, so refresh the project.

After refreshing, you can see the dump file.

Double clik the dump file, it starts MAT wizard and select the option “Leak Suspects Report” and press Finish.

It opens system overview report and displays possible problem suspects in pie chart.

Go through below link for more details about Eclipse MAT Analyzer.

https://eclipse.org/mat/

 

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