RFR: 8366363: MemBaseline accesses VMT without using lock [v3]

[Afshin Zafari]

On Tue, 2 Sep 2025 07:03:27 GMT, Johan Sjölen <jsjolen at openjdk.org> wrote:

>> Hi,
>> 
>> The `MemBaseline` used to access the VMT instance directly without a lock. We fix that, and we switch from using a `LinkedList` to a copied `RegionsTree` instead.
>
> Johan Sjölen has refreshed the contents of this pull request, and previous commits have been removed. Incremental views are not available.

When we do a `visit_in_order` we can set `next(right node)` of new nodes one by one. IOW, since Key-Values are retrieved in order, we can insert them one after another. Right?
Inspired by the `visit_in_order()` itself: there we first get `leftmost()` and then use `next()` in a loop.

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PR Comment: https://git.openjdk.org/jdk/pull/27003#issuecomment-3244624236