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Re: MAT library API

Krum Tsvetkov — 2010-01-25T11:15:13-00:00

A good question. Unfortunately I can't give you the best possible answer.

It's like this - at the moment we don't have any published documentation on how to develop with MAT APIs. There is also no javadoc published, although (most of) the API classes contain javadoc inside.

I would suggest that you start with our Wiki page for contributors:
http://wiki.eclipse.org/index.php?title=MemoryAnalyzer/Contr ibutor_Reference

It describes our SVN location and how to get started with getting and building the sources.

Most of the API is contained in the org.eclipse.mat.api plugin.

You may look into the following two classes as a starting point:

org.eclipse.mat.snapshot.SnapshotFactory

- this is how you can open a heap dump

org.eclipse.mat.snapshot.ISnapshot

- this is the "central" interface, having all the methods to get to the different classes, their instances, single objects, retained sets, etc... The interface has javadoc in it.

Currently it is not possible to generate the heap dump from within the tool. There are some efforts in this direction - see bugzilla entry https://bugs.eclipse.org/bugs/show_bug.cgi?id=229449

And about using the APIs - we are in the process of getting ready for our graduation, including our 1.0 release. In this process some of the APIs may be changed. The following bugzilla entry should track such changes: https://bugs.eclipse.org/bugs/show_bug.cgi?id=299371

I'll be very interested to get your feedback on the API if you decide to give it a try. And your feedback on the tool in general - any suggestions, comments, critique ...

Let me know if this explanation helps.

Re: download MAT for RAP

Dave Draeger — 2010-01-25T01:03:05-00:00

Is the RAP version of Memory Analyzer now available? Looks like the last indication was going to make it available in a couple of weeks, but I'm not able to find the RAP version on the MAT download pages. http://www.eclipse.org/mat/downloads.php

Can you please provide a link to where to download the RAP version? Thanks.

MAT library API

No Real Name — 2010-01-24T17:31:04-00:00

Do the MAT libraries have a documented API? I want to dynamically generate a memory dump then parse and query the resulting dump programmatically.

I can't find any documentation on this topic.

Any help would be appreciated.

Re: How to Increase heap size for MAT in IBM ISA?

Andrew Johnson — 2010-01-15T16:18:16-00:00

This help page for Memory Analyzer from IBM Support Assistant suggests the following:

Tool: IBM Monitoring and Diagnostic Tools for Java™ - Memory Analyzer > Troubleshooting
Out Of Memory Errors
Processing large dump files
Processing large dump files using Memory Analyzer may sometimes fail with a java.lang.OutOfMemoryError. The default maximum Java heap size when running ISA 4.1 is 256Mb. We recommend running Memory Analyzer with at least 512Mb.

To set the maximum heap size you can add a property value to the rcpinstall.properties file.

Updating the rcpinstall.properties file
The rcpinstall.properties file resides in the following workspace location:

For Windows:
\IBM\ISAv41\.config\rcpinstall.properties
For Linux:
/ibm/isa41/.config/rcpinstall.properties
Add or update the value for vmarg.Xmx property. For example:

vmarg.Xmx=-Xmx512m

You will need to restart ISA for the change to take effect.

Re: Need help to analyse result given by MAT

Krum Tsvetkov — 2010-01-15T11:22:48-00:00

This with the debugging is really strange. I found it while playing with the problem described here https://bugs.eclipse.org/bugs/show_bug.cgi?id=287852

I added one comment today, may be this helps the people there.

The 2 classes you see are may be ok. Look who loaded them, who keeps them, etc...

About the task manager I wouldn't worry. It does show how much memory the process reserved and uses, but doesn't reflect the state of the java heap. I mean, the memory in task manager may have grown as the java heap was resized. But this will probably stay so for a while even if GC can clean everything in the java heap.

Re: Need help to analyse result given by MAT

Aurelien Pupier — 2010-01-15T10:43:25-00:00

OMG it seems that there are no more WebAppClassLoader retained when not be in remote debug mode and without the jconsole connected...
I connected via the JConsole only at the end of repeating several times(~20) the same operation to take the dump and it seems that there were no more leaks...

Howevert I noticed that there still be 2 BirtEngine not instanciated but perhaps the GC is not passed onto it yet.

Another thing that seems to be strange is that the memory usage displayed by Windows Task Manager is increasing a little amount at each time.

But without debug mode it is hard to see exactly what happened. I hope that it is good.

Thanks for your great help

Re: Need help to analyse result given by MAT

Markus Kohler — 2010-01-15T09:32:37-00:00

From what I see in your screen shots it seems that the classloader is referenced by several "instances" of the class BirtEngine. E.g. you can load the same class more than once.
MAT reports that those BirtEngine classes are GC roots because they are referenced by native code. Unfortunately there's no information in the heap dump that could tell you which native code.
I would try to track down why and from where those BirtEngine classes are loaded.

Hope that helps,
Markus

Re: Need help to analyse result given by MAT

Aurelien Pupier — 2010-01-15T09:25:48-00:00

Thanks for your answer, it helps me a lot : it gives valuable information to explore different ways.
I will try that from now on

I am in remote debug mode and I have a jconcole connected to take dump. I will give a give a try now without that.

It seems that there is another path from GC roots, I will take a look deeper too.

Re: How to Increase heap size for MAT in IBM ISA?

Krum Tsvetkov — 2010-01-15T08:58:38-00:00

Hi Jeroen,

Thanks for pasting also the solution to your problem! I guess other users of the tool can find it helpful.

Regards,
Krum

Re: Need help to analyse result given by MAT

Krum Tsvetkov — 2010-01-15T08:54:25-00:00

Hi,

This is a very interesting question.

I think the analysis you did is very good, but the problem seems to be tricky.
You found already that the classloaders are kept after the restart of the app, and you found one path to them - the one from the BirtEngine class. This class is marked as a GC root with the reason Native Heap, which should mean there is references somewhere from the native heap. And I can't tell why.

The Merged Shrotest paths gives you only one path per object. What you could try is to run Paths From GC roots on one of the objects and see if it will return you more paths. You can also look at the inbound references to a classloader (context menu, list objects -> with incoming references).

Howefer all these are just to search for another path, and will not answer the question why the BirtEngine classes are marked as "native heap" GC roots.

BTW, I remember I have seen some of my instances marked as "Native heap" and not removed as I was debugging, had a breakpoint on this place, and was using the "All Instances" context menu in the debugger. I couldn't explain it then. Were you by chance debugging when this happened?

Does this help in any way?