How to analyse the heap dump using jmap in java

Question

I am creating heap dump using below command   jmap -dump file DumpFile txt  lt process-id gt    I have opened the generated file - DumpFile txt but it is not in readable format  So please let me know how to analyze the data in the generated file

User · Answer

You can use jhat  Java Heap Analysis Tool  to read the generated file   jhat   options    lt heap-dump-file gt    The jhat command parses a java heap dump file and launches a webserver  jhat enables you to browse heap dumps using your favorite webbrowser   Note that you should have a hprof binary format output to be able to parse it with jhat  You can use format b option to generate the dump in this format   -dump format b file  lt filename gt

User · Answer

VisualVm does not come with Apple JDK  You can use VisualVM Mac Application bundle dmg  as a separate application  to compensate for that

User · Answer

MAT  jprofiler jhat are possible options  since jhat comes with jdk  you can easily launch it to do some basic analysis  check this out

User · Answer

Very late to answer this  but worth to take a quick look at  Just 2 minutes needed to understand in detail   First create this java program  import java util ArrayList  import java util List   public class GarbageCollectionAnalysisExample      public static void main String   args               List lt String gt  l   new ArrayList lt String gt                for  int i   0  i  lt  100000000  i                        l   new ArrayList lt String gt       Memory leak                   System out println l                           System out println  Done              Use jps to find the vmid  virtual machine id i e  JVM id   Go to CMD and type below commands    C   gt jps 18588 Jps 17252 GarbageCollectionAnalysisExample 16048 2084 Main   17252 is the vmid which we need   Now we will learn how to use jmap and jhat  Use jmap - to generate heap dump    From java docs about jmap    jmap prints shared object memory maps or heap memory details of a given process or core file or a remote debug server     Use following command to generate heap dump    C   gt jmap -dump file E  heapDump jmap 17252 Dumping heap to E  heapDump jmap     Heap dump file created   Where 17252 is the vmid   picked from above    Heap dump will be generated in E  heapDump jmap  Now use Jhat Jhat is used for analyzing the garbage collection dump in java -   C   gt jhat E  heapDump jmap Reading from E  heapDump jmap    Dump file created Mon Nov 07 23 59 19 IST 2016 Snapshot read  resolving    Resolving 241865 objects    Chasing references  expect 48 dots                                                 Eliminating duplicate references                                                 Snapshot resolved  Started HTTP server on port 7000 Server is ready    By default  it will start http server on port 7000  Then we will go to http   localhost 7000   Courtesy   JMAP  How to monitor and analyze the garbage collection in 10 ways

User · Answer

If you use Eclipse as your IDE I would recommend the excellent eclipse plugin memory analyzer   Another option is to use JVisualVM  it can read  and create  heap dumps as well  and is shipped with every JDK  You can find it in the bin directory of your JDK

User · Answer

You should use jmap -heap format b  lt process-id gt  without any paths  So it creates a   bin file which you can open with jvisualvm exe  same path as jmap   It s a great tool to open such dump files

User · Answer

If you just run jmap -histo live or jmap -histo  it outputs the contents on the console

[java] How to analyse the heap dump using jmap in java

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