RFR: 8314653: Metaspace: remove allocation guard feature [v4]

[David Holmes]

On Thu, 4 Jul 2024 07:51:32 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

>> In Metaspace in debug builds, one can guard allocations. This has been a useful feature in during implementation of JEP 387 to find bugs, but has not found much use thereafter, and remains an obscure and underused feature.
>> 
>> But these guards cause quite a bit of complexity, mainly since they make testing difficult: with guards on, predicting arena growth gets quite complex.
>> 
>> I propose to remove this feature to reduce Metaspace complexity.
>> 
>> Tests: local (mac m1, Linux x64) Metaspace tests. GHAs.
>
> Thomas Stuefe 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 five additional commits since the last revision:
> 
>  - copyrights
>  - Merge branch 'master' into metaspace-remove-allocation-guard
>  - Merge branch 'openjdk:master' into metaspace-remove-allocation-guard
>  - Merge branch 'openjdk:master' into metaspace-remove-allocation-guard
>  - start

Re-approving as required under the new rules.

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Marked as reviewed by dholmes (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/19611#pullrequestreview-2158331881