RFR: 8337217: Port VirtualMemoryTracker to use VMATree [v34]

[Afshin Zafari]

On Wed, 5 Mar 2025 16:06:55 GMT, Johan Sjölen <jsjolen at openjdk.org> wrote:

>> Afshin Zafari has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   test cases for doing reserve or commit the same region twice.
>
> src/hotspot/share/nmt/memReporter.cpp line 451:
> 
>> 449:     });
>> 450: 
>> 451:     if (reserved_and_committed)
> 
> Missing braces

Done.

> src/hotspot/share/nmt/regionsTree.hpp line 37:
> 
>> 35: // for processing the tree nodes in a shorter and more meaningful way.
>> 36: class RegionsTree : public VMATree {
>> 37:  private:
> 
> Remote private, not needed.

Done.

> src/hotspot/share/nmt/regionsTree.hpp line 56:
> 
>> 54:       NodeHelper() : _node(nullptr) { }
>> 55:       NodeHelper(Node* node) : _node(node) { }
>> 56:       inline bool is_valid() { return _node != nullptr; }
> 
> Missing `const`

Done.

> src/hotspot/share/nmt/regionsTree.inline.hpp line 33:
> 
>> 31: void RegionsTree::visit_committed_regions(const ReservedMemoryRegion& rgn, F func) {
>> 32:   position start = (position)rgn.base();
>> 33:   size_t end = (size_t)rgn.end() + 1;
> 
> Can we `static_cast<size_t>(rgn.end())` instead?

Should be `reinterpret_cast<>` instead.
Done.

> src/hotspot/share/nmt/virtualMemoryTracker.cpp line 60:
> 
>> 58:     if (tracker == nullptr) return false;
>> 59:     _tracker = new (tracker) VirtualMemoryTracker(level == NMT_detail);
>> 60:     return _tracker->tree() != nullptr;
> 
> @afshin-zafari , `_tracker->tree()` can never be null anymore. In the future we should do a PR where we change it to return a reference.

Removed.

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

PR Review Comment: https://git.openjdk.org/jdk/pull/20425#discussion_r1983447519
PR Review Comment: https://git.openjdk.org/jdk/pull/20425#discussion_r1983447822
PR Review Comment: https://git.openjdk.org/jdk/pull/20425#discussion_r1983448306
PR Review Comment: https://git.openjdk.org/jdk/pull/20425#discussion_r1983449521
PR Review Comment: https://git.openjdk.org/jdk/pull/20425#discussion_r1983450068