RFR: 8337217: Port VirtualMemoryTracker to use VMATree [v8]

[Robert Toyonaga]

On Mon, 9 Dec 2024 16:38:48 GMT, Robert Toyonaga <duke at openjdk.org> wrote:

>> Only regions with the same `MemTag` can be merged into one. It is possible to have two adjacent committed regions with different `MemTag`s.
>
> Ok I see. Thank you for clarifying.

I have a couple more questions about this function:

Why bother keeping the variable `base`. It's updated whenever `prev` is updated, so why not just use `prev`?

Why do you allow for grouping two adjacent committed regions w/ diff `MemTags` together when creating `CommittedMemoryRegion`? Shouldn't they be treated as separate committed regions?  And if we are supposed to be grouping adjacent regions, shouldn't we be using the address of the first region, not the current one, when creating `CommittedMemoryRegion` (since we've been incrementing `comm_size`)?

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PR Review Comment: https://git.openjdk.org/jdk/pull/20425#discussion_r1876423806