RFR: 8330076: NMT: add/make a mandatory MEMFLAGS argument to family of os::reserve/commit/uncommit memory API [v5]

[Afshin Zafari]

On Sat, 13 Apr 2024 05:38:11 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

>> Afshin Zafari has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   mtCode and mtMetaspace were missed from System Dump map
>
> Just a thought: one (manual) test I would do would be that several JVMs run with the same conditions (I would do at least one with -Xmx=Xms and AlwaysPreTouch) accumulate the same NMT numbers, current, and peak. Just to make sure we use the same flags before and after.

Thank you @tstuefe for your review. Some changes were missed and/or not pushed. So, you should be b able to see them now.
The comment on removing MEMFLAGS from params of the `uncommit_memory` family of API is not applied since existence of the flag makes the VMATree operations more efficient.
I gather the following future PRs that you mentioned, to have individual threads of comments: 
- unify style of initialization in virtualspace.?pp code.
- check if any member can be `const`
- re-designing ReservedSpace

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PR Comment: https://git.openjdk.org/jdk/pull/18745#issuecomment-2084855905