RFR: 8300727: java/awt/List/ListGarbageCollectionTest/AwtListGarbageCollectionTest.java failed with "List wasn't garbage collected"

[Sergey Bylokhov]

On Thu, 23 Feb 2023 23:12:02 GMT, Phil Race <prr at openjdk.org> wrote:

>> I followed the piece of advice in the [JBS comment](https://bugs.openjdk.org/browse/JDK-8300727?focusedCommentId=14560139&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-14560139).
>> 
>> If using `System.gc()` is good enough for testing references:
>> 
>> https://github.com/openjdk/jdk/blob/f612dcfebea7ffd4390f833646ad45d6f0ebd04f/test/jdk/java/lang/ref/ReferenceEnqueue.java#L54-L60
>> 
>> https://github.com/openjdk/jdk/blob/f612dcfebea7ffd4390f833646ad45d6f0ebd04f/test/jdk/java/lang/ref/PhantomReferentClearing.java#L85-L92
>> 
>> Then it should be good enough for this test too.
>> 
>> Perhaps, the same effect could be achieved by causing OOME in a loop. However, using `System.gc()` makes the intention clearer: *run GC*, wait for the phantom reference to be cleared and enqueued.
>> 
>> I can explicitly select a GC: `-XX:+UseG1GC` (default) or `-XX:+UseSerialGC`.
>
> There are lots of tests that rely on System.gc() actually triggering a gc.
> SFAIK all collectors we have today will obey it unless you use
> -XX:+DisableExplicitGC
> If you can make the test work with that then that would be interesting but calling just System.gc() is no worse than all those other tests.

Many client tests generate OOM for that, we have a special Util, see the usage of Util.generateOOME() or various implementation of generateOOME.

If the OOM + sleep(to give the GC a chance to clean the weakrefs in case of slow systems) does not work, then could it be considerred as a GC bug?

>OutOfMemoryError: The Java Virtual Machine implementation has run out of either virtual or physical memory, and the automatic storage manager was unable to reclaim enough memory to satisfy an object creation request.
https://docs.oracle.com/javase/specs/jvms/se19/html/jvms-6.html#jvms-6.3

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PR: https://git.openjdk.org/jdk/pull/12594