RFR: 8319548: Unexpected internal name for Filler array klass causes error in VisualVM

[jjscl8888]

On Mon, 29 Apr 2024 07:47:35 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

> > I observed a phenomenon on our application. When there is no traffic on a certain instance, the number of old generation objects suddenly increases at a certain moment. After dumping the object instances, I found a large number of jdk.internal.vm.FillerArray objects, occupying more than 10G of memory. Have you ever encountered this?
> 
> You probably did the heap dump right after G1 managed to free lots of memory - these `FillerArray` elements represent unused memory within regions.
> 
> Previously one would have seen a huge amount of int-arrays (`[I`) staying around.
> 
> Normally G1 would then incrementally reduce these `FillerArray`s in subsequent mixed collections (after marking etc) by evacuating the live objects between these filler objects, making these regions completely empty.
> 
> From the given output of `jmap` and not knowing what else is going on with the GC this behavior seems normal.

![image](https://github.com/openjdk/jdk/assets/32790117/55cef27f-06f0-435c-b60f-3f5e48a5c5b4)
Thank you for your clarification. if the instance in question had no traffic but you observed a sudden increase in the old generation size at 2:35 in the graph, and subsequent garbage collections (GCs) did not reduce the size of the old generation back to its original value

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PR Comment: https://git.openjdk.org/jdk/pull/17155#issuecomment-2084098768