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Bug 369047

Summary:

Tracking/Comparing heap dumps

Product:

[Tools] MAT

Reporter:

Stefan Liebig <Stefan.Liebig>

Component:

GUI

Assignee:

Andrew Johnson <andrew_johnson>

Status:

RESOLVED FIXED

QA Contact:

Severity:

enhancement

Priority:

CC:

andrew_johnson

Version:

1.1

Target Milestone:

1.11.0

Hardware:

OS:

Windows 7

Whiteboard:

Bug Depends on:

361631, 561460

Bug Blocks:

Attachments:

Description	Flags
Dominator tree comparison report	none

Description Stefan Liebig

2012-01-19 04:37:52 EST

I am not quite sure if this is a reasonable request. May be there are other solutions to my problem. I am not that familiar with MAT. 

While searching for a memory leak I created several heap dumps and analyzed them (Dominator Tree). I found a lot of retained objects that simply stay with a fixed size. But others are varying in their size. And one object's size was constantly growing!
I would love to have the possibility to analyze the dominator trees of several heap dumps.

Comment 1 Andrew Johnson

2012-01-19 11:48:50 EST

I started some work to allow tree comparisons in bug 361631 but this may not be useful yet. It seems to compare using the full IObject.getDisplayName which includes the address so won't be helpful across dumps. Grouping the dominator tree by class doesn't work as I thought, as the class name includes the address.

Comment 2 Stefan Liebig

2012-01-20 01:08:16 EST

It seems that Netbeans 7.1 supports something similar: http://java.dzone.com/articles/comparing-heap-dumps-netbeans

Comment 3 Andrew Johnson

2012-01-20 03:16:30 EST

The compare basket is the standard way to compare dumps, and by comparing histogram tables you get to see how the numbers of objects differs between dumps:
http://help.eclipse.org/indigo/index.jsp?topic=%2Forg.eclipse.mat.ui.help%2Ftasks%2Fcomparingdata.html
For version 1.2 I'm looking at comparing trees as well as tables. Currently the comparison works on the original format of the tree, so even if you regroup the dominator tree by class the comparison still takes the original format of an object tree. By launching the dominator tree from the search queries command line and issuing this command:
 dominator_tree  -groupby BY_CLASS
then the dominator tree is grouped by class which might make a better base for the comparisons.

Comment 4 Andrew Johnson

2013-05-15 06:39:08 EDT

How well does comparing dominator tree by class work for you?

Comment 5 Andrew Johnson

2020-03-26 04:46:10 EDT

I know this is a very old request, but I have just made some improvements. The snapshot builds https://www.eclipse.org/mat/snapshotBuilds.php now have some queries to compare dominator trees.

See Leak Identification > Compare Snapshots Leak Report

This uses deltas in retained sizes when dominator trees from two snapshots are compared.

Comment 6 Andrew Johnson

2021-06-03 04:36:12 EDT

Created attachment 286513 [details]
Dominator tree comparison report

Example of how the Leak Suspects by Snapshot Comparison report generates a comparison of the two dominator trees
:

Comment 7 Andrew Johnson

2021-06-03 04:38:19 EDT

I hope this is sufficient, if not then please open a new enhancement request.