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The leak suspects report can generate a tree view of paths to GC roots. Sometimes this is not expanded which means the stand-alone report is not very useful. From my initial inspection of the code it seems that ISelectionProvider.EMPTY is used which returns false from isExpanded(Object row); Example: Reference Pattern Class Name Shallow Heap Retained Heap Percentage class com.ibm.p8.library.standard.xapic.XAPICClass @ 0x491dbe58 64 2,557 0.01%
Created attachment 154497 [details] Expands a tree in the HTML report This seems one way of solving the problem. Is it the right way?
This way you expand the whole tree. I tried running the component report on WeahHashMap$Entry, using the leaking-loaders sample we used at JavaOne. There it found several hundred possible leaks, and the fully expanded tree was huge. To open just one or several paths one can pass the selected paths as the third parameter to MultiplePath2GCRootsQuery.create(). We use this in the leak hunter query. I guess finding the most common path beginning (i.e. the part of the reference chains through which most of the suspects are reached) and expanding only it could be be a good alternative to show at least the "bigger" problems. Or may be expanding down to the last element (the strongly referenced WeakHashMap$Entry key) but just for some entries. Or a mixture of both - 1) find the groups which have common beginning and 2) show one full path for all of them? About the "reference pattern" example you have given above - this appears if there are no common paths going through exactly the same objects, but if there are paths going through objects of the same class, e.g. first any instance of a thread, then an instance of a HashMap, etc... There it is common to see just one or two entries.
Created attachment 281889 [details] Example of unexpanded reference pattern
Looking at this again I see that my main concern was the 'Reference Pattern' for multiple instances as leak suspects. This just showed a tree of class names up to the point where the class name was responsible for 90% of the instances. I think the tree should be a tree in the Merge Shortest Paths to GC Roots, grouped by class name. That would show the number of items at each level. Also the tree could be expanded until the number of items wasn't >= 80% of the previous level. This would expand the tree without expanding it too much. If no one class was responsible for 80% of the instances then we could still expand all the classes at the base level.
Created attachment 281890 [details] Example 1
Created attachment 281891 [details] Example 2
Two examples of how it could work. Note the expansion and the highlighting of nodes which are the end of paths (in this example 'org.eclipse.equinox.internal.p2.metadata.InstallableUnit' instances). Is expansion at 80% the right number (90% did not expand this example properly). Note the tree shows the number of objects (of that type at that level in the path) and the number of referenced suspect objects in the path.
Created attachment 281892 [details] Example 2 replaces previous
New Gerrit change created: https://git.eclipse.org/r/158120
Gerrit change https://git.eclipse.org/r/158120 was merged to [master]. Commit: http://git.eclipse.org/c/mat/org.eclipse.mat.git/commit/?id=ddcdb49bf944e669d920f7a6353f91eb3286dc4d
New Gerrit change created: https://git.eclipse.org/r/158127
Gerrit change https://git.eclipse.org/r/158127 was merged to [master]. Commit: http://git.eclipse.org/c/mat/org.eclipse.mat.git/commit/?id=2bd2502fd5409d069ac498270c367d9fb1d16dab
Krum and Kevin, I've added you to this defect so you can review the leak suspects report as this is a high profile report. This change affects a suspect report for the case of multiple object instances. It adds a pie chart and a list if some of the instances are large. Also, if there is no accumulation point then it improves the reference pattern tree (and adds a reminder if there are more than 10000 paths than it is a 'Reference pattern for 10,000 randomly chosen instances').
New Gerrit change created: https://git.eclipse.org/r/158182
Gerrit change https://git.eclipse.org/r/158182 was merged to [master]. Commit: http://git.eclipse.org/c/mat/org.eclipse.mat.git/commit/?id=0ab47c1d8cbaf0953fe86b125b76bed4d61494e4
I'll mark this as complete for 1.10
