RFR: 8343704: Bad GC parallelism with processing Cleaner queues [v10]

[Chen Liang]

On Fri, 15 Nov 2024 19:30:06 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> See the bug for more discussion and reproducer. This PR replaces the ad-hoc linked list with segmented list of arrays. Arrays are easy targets for GC. There are possible improvements here, most glaring is parallelism that is currently knee-capped by global synchronization. The synchronization scheme follows what we have in original code, and I think it is safer to continue with it right now.
>> 
>> I'll put performance data in a separate comment.
>> 
>> Additional testing:
>>  - [x] Original reproducer improves drastically
>>  - [x] New microbenchmark shows no regression on "churning" tests, which covers insertion/removal perf
>>  - [x] New microbenchmark shows improvement on Full GC times (crude, but repeatable), serves as a proxy for reproducer
>>  - [x] `java/lang/ref` tests in release 
>>  - [x] `all` tests in fastdebug
>
> Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision:
> 
>   prev is not needed

test/jdk/jdk/internal/ref/Cleaner/CleanableListTest.java line 30:

> 28:  * @compile/module=java.base jdk/internal/ref/CleanableListTestHelper.java jdk/internal/ref/TestCleanable.java
> 29:  * @modules java.base/jdk.internal.ref
> 30:  * @run testng/othervm --add-exports java.base/jdk.internal.ref=ALL-UNNAMED CleanableListTest

I don't think you need this --add-exports flag; JTReg modules tag should take care of it for you.

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PR Review Comment: https://git.openjdk.org/jdk/pull/22043#discussion_r1845168888