RFR: 8337217: Port VirtualMemoryTracker to use VMATree [v41]

[Gerard Ziemski]

On Tue, 17 Jun 2025 10:17:06 GMT, Afshin Zafari <azafari at openjdk.org> wrote:

>> - `VMATree` is used instead of `SortedLinkList` in new class `VirtualMemoryTracker`.
>>  -  A wrapper/helper `RegionTree` is made around VMATree to make some calls easier.
>>  - `find_reserved_region()` is used in 4 cases, it will be removed in further PRs.
>>  - All tier1 tests pass except this https://bugs.openjdk.org/browse/JDK-8335167.
>
> Afshin Zafari has updated the pull request incrementally with one additional commit since the last revision:
> 
>   fixes to a few failures.

Small changes (copyright years) and one question, otherwise LGTM.

Nice!

Marked as reviewed by gziemski (Reviewer).

src/hotspot/share/nmt/regionsTree.cpp line 2:

> 1: /*
> 2:  * Copyright (c) 2024, Oracle and/or its affiliates. All rights reserved.

Copyright year

src/hotspot/share/nmt/regionsTree.hpp line 2:

> 1: /*
> 2:  * Copyright (c) 2024, Oracle and/or its affiliates. All rights reserved.

Copyright year

test/hotspot/gtest/runtime/test_virtualMemoryTracker.cpp line 259:

> 257:   static void test_add_committed_region_overlapping() {
> 258:     RegionsTree* rtree = VirtualMemoryTracker::Instance::tree();
> 259:     rtree->tree().remove_all();

Why are we calling `remove_all()` right after we create the tree?

-------------

Marked as reviewed by gziemski (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/20425#pullrequestreview-2936231261
PR Review: https://git.openjdk.org/jdk/pull/20425#pullrequestreview-2936387120
PR Review Comment: https://git.openjdk.org/jdk/pull/20425#discussion_r2152711203
PR Review Comment: https://git.openjdk.org/jdk/pull/20425#discussion_r2152711676
PR Review Comment: https://git.openjdk.org/jdk/pull/20425#discussion_r2152621722