> This is the 3rd PR for [JEP 483: Ahead-of-Time Class Loading & > Linking](https://bugs.openjdk.org/browse/JDK-8315737). > > **Overview** > > - A new `-XX:+AOTClassLinking` flag is added. See [JEP > 498](https://bugs.openjdk.org/browse/JDK-8315737) and the > [CSR](https://bugs.openjdk.org/browse/JDK-8339506) for a discussion of this > command-line option, its default value, and its impact on compatibility. > - When this flag is enabled during the creation of an AOT cache (aka CDS > archive), an `AOTLinkedClassTable` is added to the cache to include all > classes that are AOT-linked. For this PR, only classes for the > boot/platform/application loaders are eligible. The main logic is in > `aotClassLinker.cpp`. > - When an AOT archive is loaded in a production run, all classes in the > `AOTLinkedClassTable` are loaded into their respective class loaders at the > earliest opportunity. The main logic is in `aotLinkedClassBulkLoader.cpp`. > - The boot classes are loaded as part of `vmClasses::resolve_all()` > - The platform/application classes are loaded after the module graph is > restored (see changes in `threads.cpp`). > - Since all classes in a `AOTLinkedClassTable` are loaded before any > user-code is executed, we can resolve constant pool entries that refer to > these classes during AOT cache creation. See changes in > `AOTConstantPoolResolver::is_class_resolution_deterministic()`. > > **All-or-nothing Loading** > > - Because AOT-linked classes can refer to each other, using direct C++ > pointers, all AOT-linked classes must be loaded together. Otherwise we will > have dangling C++ pointers in the class metadata structures. > - During a production run, we check during VM start-up for incompatible VM > options that would prevent some of the AOT-linked classes from being loaded. > For example: > - If the VM is started with an JVMTI agent that has ClassFileLoadHook > capabilities, it could replace some of the AOT-linked classes with > alternative versions. > - If the VM is started with certain module options, such as > `--patch-module` or `--module`, some AOT-linked classes may be replaced with > patched versions, or may become invisible and cannot be loaded into the JVM. > - When incompatible VM options are detected, the JVM will refuse to load an > AOT cache that has AOT-linked classes. See > `FileMapInfo::validate_aot_class_linking()`. > - For simplfication, `FileMapInfo::validate_aot_class_linking()` requires > `CDSConfig::is_using_full_module_graph()` to be true. This means that the > exact same set of modules are visible whe...
Ioi Lam has updated the pull request incrementally with one additional commit since the last revision: @dholmes-ora comments ------------- Changes: - all: https://git.openjdk.org/jdk/pull/20843/files - new: https://git.openjdk.org/jdk/pull/20843/files/a5e7eb51..ac1ed798 Webrevs: - full: https://webrevs.openjdk.org/?repo=jdk&pr=20843&range=01 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=20843&range=00-01 Stats: 61 lines in 7 files changed: 29 ins; 15 del; 17 mod Patch: https://git.openjdk.org/jdk/pull/20843.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/20843/head:pull/20843 PR: https://git.openjdk.org/jdk/pull/20843
