RFR: 8309240: Array classes should be stored in dynamic CDS archive [v3]

[David Holmes]

On Thu, 27 Jul 2023 19:39:04 GMT, Calvin Cheung <ccheung at openjdk.org> wrote:

>> Please review this RFE for adding array classes in the dynamic CDS archive.
>> 
>> During dynamic dump, only the array classes with the `element_klass` already in the static archive will be stored in the dynamic archive. See `ArchiveBuilder::gather_array_klasses()`. It is because the array classes which are in the same archive (either static or dynamic) are already "connected" together. Higher dimension primitive array classes are also stored in the dynamic archive. Note that one-dimensional primitive array classes are store in the static archive.
>> 
>> During runtime, the `DynamicArchive::setup_array_klasses()` is for setting up the array classes. If only the `bottom_klass` is in the static archive, the function will point the `array_klasses` to the stored array classes in the dynamic archive. If a lower dimension array class is already in the static archive, its `higher_dimension` will be set to refer to the stored array classes in the dynamic archive.
>> 
>> Some logging is added to `ObjArrayKlass::array_klass(int n, TRAPS)` to indicate an array class is being loaded from the archive.
>> 
>> Passed tiers 1 - 4 testing.
>
> Calvin Cheung has updated the pull request incrementally with one additional commit since the last revision:
> 
>   @iklam comments

src/hotspot/share/cds/dynamicArchive.cpp line 435:

> 433:       if (elm->is_instance_klass()) {
> 434:         assert(InstanceKlass::cast(elm)->array_klasses() == nullptr, "must be");
> 435:         InstanceKlass::cast(elm)->release_set_array_klasses(oak);

I know you were asked to use this here but a release operation only has meaning when paired with an acquire - so where is the matching acquire?

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PR Review Comment: https://git.openjdk.org/jdk/pull/14959#discussion_r1276883057