On Wed, 13 Nov 2024 20:33:25 GMT, Aleksey Shipilev <sh...@openjdk.org> wrote:
>> See the bug for more discussion and reproducer. This PR replaces the ad-hoc
>> linked list with the `ArrayList` wrapper that manages synchronization,
>> search and replacements efficiently. 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:
>
> Review feedback: make sure trimming actually works, stylistic changes
src/java.base/share/classes/jdk/internal/ref/CleanerImpl.java line 236:
> 234: static final class PhantomCleanableList {
> 235: private static final int MIN_CAPACITY = 16;
> 236: private final Object lock = new Object();
Why use another lock object when identity of this list is not escaped elsewhere?
src/java.base/share/classes/jdk/internal/ref/CleanerImpl.java line 311:
> 309: // want to cause an immediate resize on next insertion.
> 310: if ((size < arr.length / 4) && (size > MIN_CAPACITY)) {
> 311: int newLen = ArraysSupport.newLength(size, 1, size);
This code isn't immediately clear that it's trying to half the array size, as
you are using the size computation method for array growth. Can you add a
remark for so?
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/22043#discussion_r1841375400
PR Review Comment: https://git.openjdk.org/jdk/pull/22043#discussion_r1841378770
