RFR: 8336463: Parallel: Add PSOldGen::expand_and_allocate

[Zhengyu Gu]

On Tue, 16 Jul 2024 16:34:52 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

>> Okay, let me ask in a different way: why use `cas_allocate_noexpand()` here, which implies there may be other threads (e.g. GC threads) that may perform allocation concurrently?
>
> There is no non-cas version API for allocate. Maybe I can add a comment to explain, sth like, "Reuse the CAS API even though this is VM thread in safepoint. This method is not invoked repeated, so the CAS overhead should be negligible."?

Thank you for the explanation. A comment will be good.

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PR Review Comment: https://git.openjdk.org/jdk/pull/20189#discussion_r1679754519