RFR: Restrict generational mode to adaptive heuristic [v2]

[Aleksey Shipilev]

On Tue, 28 Mar 2023 18:31:45 GMT, William Kemper <wkemper at openjdk.org> wrote:

>> This is a small change to Shenandoah, but it prevents us from running the tests with the generational mode enabled via a jtreg vm option. This requires us to properly integrate the generational mode with the jtreg tests. There are many test files changed, but the `generational` mode is now handled in the same fashion as other modes (`iu`, `passive`). There are two additional advantages to these changes:
>> * We no longer need to run the test suite twice (once in the default mode and again with `-XX:ShenandoahGCMode=generational`).
>> * Expanded test coverage, as some tests would spawn their own VMs with permutations of mode and heuristic options that ignored the generational mode.
>
> William Kemper 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 12 additional commits since the last revision:
> 
>  - Put verify option on separate line
>  - Add generational modes to the test
>  - Allow more memory for young generation
>  - Update test to use shenandoah young gen pool when appropriate
>  - Add generational mode test case
>  - Don't make default mode explicit for consistency with other tests
>  - Fix errors, improve test summaries
>  - WIP: Bug fixes, add generational mode to more tests
>  - WIP: Integrate generational mode with more tests
>  - Restrict young generation adaptive heuristic
>  - ... and 2 more: https://git.openjdk.org/shenandoah/compare/a7ad66ba...28509ca0

test/hotspot/jtreg/gc/shenandoah/oom/TestAllocOutOfMemory.java line 90:

> 88:                           "-XX:+UseShenandoahGC",
> 89:                           TestAllocOutOfMemory.class.getName(),
> 90:                           "test", args[0]);

Suggestion: pull `args[0]` into the local variable.

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PR Review Comment: https://git.openjdk.org/shenandoah/pull/233#discussion_r1151542108