RFR: 8351661: NMT: VMATree should support separate call-stacks for reserve and commit operations [v2]

[Gerard Ziemski]

On Thu, 13 Mar 2025 13:13:15 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:
> 
>   fixed a bug.

Changes requested by gziemski (Reviewer).

src/hotspot/share/nmt/vmatree.cpp line 100:

> 98:         stB.in.set_stack(leqA_n->val().out.stack());
> 99:         stA.out.set_second_stack(metadata.stack_idx);
> 100:         stB.in.set_second_stack(metadata.stack_idx);

Did we consider naming them differently?

One obvious choice would be ReserveStack and CommitStack?

Right now, we need to mentally map them one way, and I am afraid that we could possibly get it reversed at some other point in code...

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PR Review: https://git.openjdk.org/jdk/pull/24028#pullrequestreview-2682612623
PR Review Comment: https://git.openjdk.org/jdk/pull/24028#discussion_r1993880091