On Mon, 9 Sep 2024 16:51:35 GMT, Chris Plummer <cjplum...@openjdk.org> wrote:
>> There is no dedicated klass field anymore, the Klass* is encoded in the >> mark, and we would need to extract it. What is the purpose of the visitors? >> Do they need to see the klass/compressedKlass, or is it sufficient to visit >> the mark-word (which we already do, but as CInt). > > I've been looking into this. It's a bit hard to follow but I think you do > need to do something more here. Can you run ClhsdbInspect.java and send me > the output. In specific I need to know if the log includes the following: > > > hsdb> + inspect 0x00000007cff154b8 > instance of Oop for > java/util/concurrent/locks/AbstractQueuedSynchronizer$ConditionObject @ > 0x00000007cff154b8 (size = 24) > _mark: 1 > _metadata._compressed_klass: InstanceKlass for > java/util/concurrent/locks/AbstractQueuedSynchronizer$ConditionObject > firstWaiter: Oop for > java/util/concurrent/locks/AbstractQueuedSynchronizer$ConditionNode @ > 0x00000007cfff5f80 > lastWaiter: Oop for > java/util/concurrent/locks/AbstractQueuedSynchronizer$ConditionNode @ > 0x00000007cfff5f80 > this$0: Oop for java/util/concurrent/locks/ReentrantLock$NonfairSync @ > 0x00000007cff15498 I pulled your changes and I see one slight difference in the output. The following line is missing: `_metadata._compressed_klass: InstanceKlass for java/util/concurrent/locks/AbstractQueuedSynchronizer$ConditionObject` I realize that there is no `_metadata._compressed_klass` when you have compact headers, and that the Klass* is encoded in the `_mark` word, which is now looks something like this in the output: _mark: 16294762323640321 So you can say that the Klass* is embedded in the _mark work, but this isn't of much help to SA users. I think what is expected is that the visitor is passed a MetadataField object that when getValue() is called on it, the Klass mirror is returned. Maybe we need a new CompactKlassField type like we current have a NarrowKlassField field type, and it will do the decoding of the _mark work into a Klass. The current getKlass() is related to this. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/20677#discussion_r1750743693
