RFR: 8343704: Bad GC parallelism with processing Cleaner queues [v4]

[Aleksey Shipilev]

On Thu, 14 Nov 2024 10:00:24 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> Speaking of testing, with this level of change, perhaps a new (white box?) regtest is warranted.
>
> I see that existing `Cleaner` tests are quite rich already. Array-based implementation does rise question about testing the resizes, that's obvious. But I have discovered that copying arrays is not really that good in this scenario which balloons cleaner lists and shrinks them rapidly in our reproducers. So I have reimplemented the whole thing as the linked list of arrays, which makes capacity management code much less problematic. The new asserts around that code should IMO test enough with existing tests.

Nevermind, I added a directed regression test for it now.

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PR Review Comment: https://git.openjdk.org/jdk/pull/22043#discussion_r1842210127