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

[David Holmes]

On Wed, 20 Dec 2023 10:15:44 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

>> Hi all,
>> 
>>   please review this change that changes the filler array class name (again) after user feedback.
>> 
>> In particular, the previous name `Ljdk/internal/vm/FillerArray;` confuses some tools (https://github.com/oracle/visualvm/issues/523). I.e. it's not an array, but still variable sized.
>> This change adds the `[` array bracket, and renames the element name to not have `Array` inside to not try to pretend that the element is some other kind of array.
>> 
>> Testing: tier1-6
>> 
>> Thanks,
>>   Thomas
>
> Fwiw, the original issue introducing details the advantages too https://bugs.openjdk.org/browse/JDK-8284435; it does not particularly point out how much memory this saves, but it mentions that it removes the need for keeping around an extra mark bitmap covering the whole Java heap (that 1.5%).

Thanks for clarifying @tschatzl that these pretend arrays are only exposed in this one case.

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PR Comment: https://git.openjdk.org/jdk/pull/17155#issuecomment-1865383374