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

[Thomas Schatzl]

On Sun, 28 Apr 2024 08:25:34 GMT, jjscl8888 <duke 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.

-------------

PR Comment: https://git.openjdk.org/jdk/pull/17155#issuecomment-2082081516