RFR: 8350550: Preload classes from AOT cache during VM bootstrap [v11]

[Vladimir Kozlov]

On Tue, 23 Sep 2025 03:24:28 GMT, Ioi Lam <iklam at openjdk.org> wrote:

>> This PR loads the classes for the boot/platform/app loaders with `AOTLinkedClassBulkLoader::preload_classes()`. This happens at the very beginning of `vmClasses::resolve_all()`, before any Java code is executed. 
>> 
>> - We essentially iterate over all the classes inside the `AOTLinkedClassTable` and adds them into the system dictionary using the new method `SystemDictionary::preload_class()`.
>> - `SystemDictionary::preload_class(..., k)` is lightweight because it's called in a single thread after all super types of `k` have been loaded. So most of the complicated work (such as place holders, circularity detection, etc) in `SystemDictionary::resolve_or_null(..., k)` can be skipped. We also don't need to call into `ClassLoader::load_class()` as the boot/platform/app loaders are well-behaved.
>> - In the assembly phase, we record the mirror, package, protection domain, code source, etc, of these classes. So there's no need to programmatically create them in the production run. See `HeapShared::copy_java_mirror()` and also changes in ClassLoader.java and SecureClassLoader.java.
>
> Ioi Lam has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 31 commits:
> 
>  - @vnkozlov review comments
>  - Merge branch 'master' into 8350550-preload-aot-classes-during-vm-bootstrap
>  - @ashu-mehra comment - AOTLinkedClassBulkLoader::link_or_init_javabase_classes() should also call exit_on_exception()
>  - Fixed 32-bit builds
>  - Removed JVMCI-specific checks that are no longer necessary with class preloading -- all CP entries discoverable by JVMCI will always point to already-loaded classes
>  - Simplify implementation after JDK-8367366: Do not support -XX:+AOTClassLinking for dynamic CDS archive
>  - Merge branch 'master' into 8350550-preload-aot-classes-during-vm-bootstrap
>  - Merge branch 'master' into 8350550-preload-aot-classes-during-vm-bootstrap
>  - @ashu-mehra comment: removed AOTLinkedClassBulkLoader::is_pending_aot_linked_class
>  - @ashu-mehra review comments
>  - ... and 21 more: https://git.openjdk.org/jdk/compare/61c5245b...bd08a0b5

Good.

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Marked as reviewed by kvn (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/26375#pullrequestreview-3258111898