RFR: 8366241: NMT: Consolidate [Virtual/Committed/Reserved]Regions into one structure [v4]

[Johan Sjölen]

On Mon, 29 Sep 2025 09:37:44 GMT, Afshin Zafari <azafari at openjdk.org> wrote:

>> The structures `CommittedMemoryRegion` and `ReservedMemoryRegion` are merged into the `VirtualMemoryRegion`.
>> 
>> Tests:
>> tiers1-5, main platforms, debug/product
>
> Afshin Zafari has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains seven commits:
> 
>  - Merge remote-tracking branch 'origin/master' into _8366241_nmt_consolidate_structures
>  - Merge remote-tracking branch 'origin/master' into _8366241_nmt_consolidate_structures
>  - master merge fix
>  - Merge remote-tracking branch 'origin/master' into _8366241_nmt_consolidate_structures
>  - after merge with 8366363.
>  - Merge remote-tracking branch 'origin/master' into _8366241_nmt_consolidate_structures
>  - 8366241: NMT: Consolidate [Virtual/Committed/Reserved]Regions into one structure

src/hotspot/share/nmt/virtualMemoryTracker.hpp line 196:

> 194:  */
> 195: class VirtualMemoryRegion {
> 196:  private:

Style, pre-existing: Remove this private as it's private by default at the start.

src/hotspot/share/nmt/virtualMemoryTracker.hpp line 200:

> 198:   size_t          _size;
> 199:   MemTag          _mem_tag;
> 200:   NativeCallStack _reserved_stack, _committed_stack;

Style: Please separate out these into two declarations on two lines.

src/hotspot/share/nmt/virtualMemoryTracker.hpp line 236:

> 234: 
> 235:   inline bool contain_address(address addr) const {
> 236:     assert(is_valid(), "snaity");

"sanity"

src/hotspot/share/nmt/virtualMemoryTracker.hpp line 244:

> 242:     assert(sz > 0, "Invalid size");
> 243:     assert(size() > 0, "Invalid size");
> 244:     assert(is_valid(), "snaity");

"sanity"

src/hotspot/share/nmt/virtualMemoryTracker.hpp line 265:

> 263:   inline bool equals(const VirtualMemoryRegion& rgn) const {
> 264:     return compare(rgn) == 0;
> 265:   }

Is this used?

src/hotspot/share/nmt/virtualMemoryTracker.hpp line 273:

> 271:   bool is_valid() const { return base() != nullptr && size() != 0;}
> 272: 
> 273:   inline void  set_reserved_call_stack(const NativeCallStack& stack) { _reserved_stack = stack; }

Is this used? Doesn't it make more sense for these values to be constant and the VMR to be an immutable object (in essence).

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PR Review Comment: https://git.openjdk.org/jdk/pull/27137#discussion_r2388569129
PR Review Comment: https://git.openjdk.org/jdk/pull/27137#discussion_r2388582133
PR Review Comment: https://git.openjdk.org/jdk/pull/27137#discussion_r2388570928
PR Review Comment: https://git.openjdk.org/jdk/pull/27137#discussion_r2388571464
PR Review Comment: https://git.openjdk.org/jdk/pull/27137#discussion_r2388573486
PR Review Comment: https://git.openjdk.org/jdk/pull/27137#discussion_r2388575968