RFR: 8343704: Bad GC parallelism with processing Cleaner queues [v14]

[Brent Christian]

On Thu, 21 Nov 2024 19:29:07 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> Ah (facepalms), I see, I thought I assigned it! Damn. Let me fix and re-measure.
>
> Redone the benchmark. We actually want all targets to be reachable, and only expose the Cleaner-side linked lists to the test. New performance data is updated here: https://github.com/openjdk/jdk/pull/22043#issuecomment-2470928360

Would this be considered a benchmark of the GC's PhantomReference management, then - deciding that all the `PhantomCleanerRef`s are still reachable, perhaps?

To measure `CleanableList`'s list manipulation at GC-time, a `Target` needs to become unreachable, so its `PhantomCleanerRef` will come off the `ReferenceQueue` (CleanerImp.java L140). Right?

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PR Review Comment: https://git.openjdk.org/jdk/pull/22043#discussion_r1853110692