RFR: Account for humongous object waste

[William Kemper]

On Fri, 14 Apr 2023 23:22:54 GMT, Y. Srinivas Ramakrishna <ysr at openjdk.org> wrote:

>> The unused portion of the last region in a humongous object is now tracked and logged.
>
> src/hotspot/share/gc/shenandoah/shenandoahVerifier.cpp line 425:
> 
>> 423: 
>> 424:     if (!generation->is_global()) {
>> 425:       // Humongous waste is currently only tracked for young and old generations
> 
> Why?
> 
> (May be this gets back to my question about where and how this statistic is being used or being planned to be used.)

I will try to change this. Ultimately, I want the "global" generation to subsume the usage metrics currently tracked in `ShenandoahHeap`.

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PR Review Comment: https://git.openjdk.org/shenandoah/pull/255#discussion_r1167344393