RFR: 8346920: Serial: Support allocation in old generation before GC [v2]

[Albert Mingkun Yang]

On Mon, 6 Jan 2025 14:36:23 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

>> This PR introduces a new strategy to determine whether an allocation should be attempted in the old generation or if a GC cycle should be initiated, based on the `GCTimeRatio`. With this change, the benchmark attached to the ticket now completes in ~13 GC, a significant improvement compared to the >1000 GC observed previously.
>> 
>> Test: tier1-3
>
> Albert Mingkun Yang 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 three additional commits since the last revision:
> 
>  - review
>  - Merge branch 'master' into s1-gc-time-ratio
>  - s1-gc-time-ratio

Superseded by https://github.com/openjdk/jdk/pull/23270, where it doesn't use `GCTimeRatio` and affects only tight-heap configurations.

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PR Comment: https://git.openjdk.org/jdk/pull/22899#issuecomment-2610079116