RFR: Account for humongous object waste

[William Kemper]

On Mon, 17 Apr 2023 19:00:02 GMT, Y. Srinivas Ramakrishna <ysr at openjdk.org> wrote:

>> I'm not sure I follow. This closure visits every region. We don't want to count the `free` portions of regular/in-use regions as humongous waste.
>
> I see the source of my confusion. A region is designated humongous only when it holds a humongous object (we don't reserve humongous regions a priori). Thus, the test `r->is_humongous` a fortiori implies `r->used() > 0`. Sorry for my confusion. 
> 
> I also realize now that this is used only during verification, which I hadn't realized before.
> 
> All good.

> a fortiori
>: with greater reason or more convincing force —used in drawing a conclusion that is inferred to be even more certain than another

TIL (Today I Learned)

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PR Review Comment: https://git.openjdk.org/shenandoah/pull/255#discussion_r1169253961