RFR: 8312132: Add tracking of multiple address spaces in NMT [v54]

[Thomas Stuefe]

On Mon, 29 Apr 2024 19:34:41 GMT, Gerard Ziemski <gziemski at openjdk.org> wrote:

>> Johan Sjölen has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   assert device != nullptr in MemoryFileTracker::instance
>
> src/hotspot/share/nmt/vmatree.cpp line 29:
> 
>> 27: #include "utilities/growableArray.hpp"
>> 28: 
>> 29: VMATree::SummaryDiff VMATree::register_mapping(size_t A, size_t B, StateType state,
> 
> Does `VMATree` stand for "Virtual Memory Allocation Tree"?
> 
> We have some long name already in nmt, ex: `NativeCallStackStorage`, `MemoryFileTracker`, `MallocSiteHashtableEntry`, `MemSummaryDiffReporter`. Can we then name it: `VirtualMemAllocationTree` or `VirtualMemAllocTree` or `VirtMemAllocTree` ?

@gerard-ziemski I originally chose "VMA" because its a clearly defined acronym in linux and has close pendants in other OSes as well. I like its brevity. 

If we really want to rename it, I would name it something like `IntervalTree`. Since that's what it really is - managing sets of numeric intervals with attributes. But IMHO VMATree is fine.

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PR Review Comment: https://git.openjdk.org/jdk/pull/18289#discussion_r1584195115