RFR: 8328944: NMT reports "unknown" memory [v2]

[Afshin Zafari]

On Tue, 19 Nov 2024 22:01:13 GMT, Gerard Ziemski <gziemski at openjdk.org> wrote:

>> We use `mtNone` value in several functions default parameters, which may show up in NMT reports.
>> 
>> We address this, by avoiding using `mtNone`.
>> 
>> Eventually the goal would be to eliminate using `mtNone` whenever possible.
>> TODO: update copyrights.
>> 
>> Testing: undergoing MARCH5 tier1-5 ...
>
> Gerard Ziemski has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains six additional commits since the last revision:
> 
>  - avoid using mtNone
>  - Merge remote-tracking branch 'upstream/master' into JDK-8328944
>  - revert, we will re-do with a smaller change
>  - remove more mtNone
>  - remove API that allows to change the mem_tag for virtual memory, feedback
>  - do not allow default parameter for mtNone

src/hotspot/share/memory/virtualspace.hpp line 65:

> 63: 
> 64:   void initialize(size_t size, size_t alignment, size_t page_size,
> 65:                   char* requested_address, bool executable, MemTag mem_tag = mtNone);

When `mtNone` is default, it is still possible to introduce/create regions of Unknown types. The MemTag arg should be mandatory.

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PR Review Comment: https://git.openjdk.org/jdk/pull/21843#discussion_r1850003383