RFR: 8337217: Port VirtualMemoryTracker to use VMATree [v33]

[Afshin Zafari]

On Tue, 4 Mar 2025 09:23:08 GMT, Johan Sjölen <jsjolen at openjdk.org> wrote:

>> test/hotspot/gtest/nmt/test_regions_tree.cpp line 98:
>> 
>>> 96:   rt.reserve_mapping(1400, 50, rd);
>>> 97: 
>>> 98:   rt.commit_region((address)1010, 5UL, ncs);
>> 
>> What would, what should happen if we repeat the same reserve_mapping?
>> 
>> rt.commit_region((address)1010, 5UL, ncs);
>> rt.commit_region((address)1010, 5UL, ncs);
>> 
>> Are/should we be allowed to do this?
>
> Nothing would happen, the state of the tree would stay the same. We should allow it, at least on product builds! For me, the most important part of this rewrite is getting rid of NMT crashing because it reaches states that it can't do anything with. We can handle more usage patterns, and we try our darnest to not fail.

The test `TEST_VM_F(NMTRegionsTreeTest, ReserveCommitTwice)` is added.

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PR Review Comment: https://git.openjdk.org/jdk/pull/20425#discussion_r1979094540