RFR: 8363932: G1: Better distribute KlassCleaningTask [v2]

[Thomas Schatzl]

On Mon, 22 Sep 2025 08:04:30 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

> Preexisting: These two methods, `subklass` and `next_sibling`, sounds like plain getters, but they actually query liveness and skip dead klasses. I wonder whether it's possible to prune dead klasses in one go at some place and turn these two methods into plain getters.

In my limited understanding of this part of the VM, apart from renaming them, I do not see a good way to improve the code. The klass graph walks may be concurrent to removing them, so at best the dead links could be ignored. The current implementation fixes them up at the same time as walking as well, which is arguable either way to me.

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PR Comment: https://git.openjdk.org/jdk/pull/27316#issuecomment-3322952079