[jdk25u] RFR: 8359947: GenShen: use smaller TLABs by default

[Aleksey Shipilev]

On Mon, 18 Aug 2025 20:59:53 GMT, William Kemper <wkemper at openjdk.org> wrote:

> Clean backport. This is a performance improvement for the generational mode of Shenandoah.

On further thought and reading through the set of mainline experiments, I suspect we should really do this after the CAS allocation path is done? This would mitigate any problems with contention on heap lock with smaller TLABs.

(The synopsis is also misleading, since it also affects non-generational Shenandoah -- but there is nothing to be done at this point.)

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PR Comment: https://git.openjdk.org/jdk25u/pull/99#issuecomment-3223859711