RFR: 8351661: NMT: VMATree should support separate call-stacks for reserve and commit operations [v8]

[Afshin Zafari]

On Mon, 7 Apr 2025 12:37:30 GMT, Afshin Zafari <azafari at openjdk.org> wrote:

>> In NMT detail mode, we need to have separate call-stacks for Reserve and Commit operations.
>> This PR adds a second stack to every node that will be used when committing (and uncommitting) the start node of a reserved region.
>
> Afshin Zafari has updated the pull request incrementally with one additional commit since the last revision:
> 
>   fixes. New check_tree impl and visualization.

Dear Reviewers,
In the `test_vmatree.cpp` at test `NMTVMATreeTest.SeparateStacksForCommitAndReserve`, the nodes in the tree and their metadata are visualized in commented lines. A new data-structure is also introduced to use the info in the visualization for checking (using the `check_tree` function) the actual and expected values in a tree. The structure and the visulazation are made similar as much as possible. One can use the comments first to analyze the test-case and then use the structure and the function to check expected results. Or, the structure alone can be used both as illustration and checking.

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PR Comment: https://git.openjdk.org/jdk/pull/24028#issuecomment-2783204779