RFR: 8337217: Port VirtualMemoryTracker to use VMATree [v32]

[Gerard Ziemski]

On Thu, 27 Feb 2025 13:25:35 GMT, Johan Sjölen <jsjolen at openjdk.org> wrote:

>> Afshin Zafari has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   removed UseFlagInPlace test.
>
> src/hotspot/share/nmt/memTracker.hpp line 60:
> 
>> 58:   static bool walk_virtual_memory(VirtualMemoryWalker* walker) {
>> 59:     return VirtualMemoryTracker::Instance::walk_virtual_memory(walker);
>> 60:   }
> 
> The `MemTracker` API exposes the outer and locking implementation to the rest of Hotspot. These two methods are used by us internally. I think it's better if these methods are deleted and the `VirtualMemoryTracker::Instance` methods are called directly, instead.

Not sure I agree with Johan's comment here - in memBaseline.cpp we use MemTracker a lot, so adding these APIs make sense there, otherwise we would have to split work between MemTracker and VirtualMemoryTracker.

Personally I like this way better.

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PR Review Comment: https://git.openjdk.org/jdk/pull/20425#discussion_r1974077639