RFR: 8193213 & 8182731: Make the UseAppCDS option obsolete

Jiangli Zhou jiangli.zhou at Oracle.COM
Wed Apr 25 00:53:24 UTC 2018

Please review the following changes that streamline the support for application class data sharing by eliminating the requirement of using -XX:+UseAppCDS to enable the feature. The support for application class data sharing is now enabled transparently when application classes or platform classes present in the classlist or generated archive with -Xshare:dump/on/auto.

	RFE: https://bugs.openjdk.java.net/browse/JDK-8193213
	Bug: https://bugs.openjdk.java.net/browse/JDK-8182731
	webrev: http://cr.openjdk.java.net/~jiangli/8193213_8182731/webrev.00/

Highlights of the changes:
* UseAppCDS is obsolete in JDK 11
* Remove the +UnlockCommercialFeatures requirement when using application class data sharing in OracleJDK binary
* SharedArchiveFile is a product flag for all configurations in JDK 11
* DumpLoadedClassList produces a complete classlist including all loaded library and application classes

Thanks David Holmes for his guidance on CSR process.

Following are the details for the VM and test changes:
- Removed various ‘if (UseAppCDS)’ checks and UseAppCDS asserts.

- Removed some of the CDS/AppCDS specifics from general class loading code.

- Removed scattered checks for non-empty directory. Dump time non-empty directory check is done at one central place, FileMapInfo::check_nonempty_dir_in_shared_path_table() after loading all classes on the classlist. The behavior is backwards compatible:
  - If no app/platform classes are loaded, dump time only reports error if non-empty directory exists in -Xbootclasspath/a path 
  - If app/platform classes are loaded, dump time reports error for any non-empty directory exists in -Xbootclasspath/a path, class path, or module path

- Removed unnecessary ‘if (!DumpSharedSpaces)’ from SharedClassUtil::initialize(). The code path is only executed when UseSharedSpaces is enabled. 

- Return immediately in SystemDictionaryShared::find_or_load_shared_class() if the archive header indicates there is no app or platform classes in the shared archive. This reduces overhead in class loading if the shared archive only contains system classes. It also provides backwards compatibility in cases where shared application classes should be disabled. For example, when the default system class loader is replaced by user provided loader, archived application classes are inactive (not loaded from archive) at runtime without affecting the use of archived system classes.

- Changed GenerateLinkOptData.gmk to filter out HelloClasslist from the default classlist in JDK image, which is generated using DumpLoadedClassList option. Thanks for David and Ioi's input on this.

- Updated various cds/appcds tests to reflect the JVM changes. The use of -XX:+UseAppCDS in tests remains unchanged.

  - Removed -XX:+UnlockCommercialFeatures for -XX:+UseAppCDS in tests

  - Removed -XX:+UnlockDiagnosticVMOptions for -XX:SharedArchiveFile in tests

  - Updated NonBootLoaderClasses.java: ensure app/platform classes on classlist are archived without -XX:+UseAppCDS

  - Updated DirClasspathTest.java: reflect the change for non-empty directory handling

  - Updated MismatchedUseAppCDS.java:  -XX:-UseAppCDS has no effect

Tested with all cds and appcds tests locally with both fastdebug and release builds. Tested with hs-teir1, hs-tier2, jdk-tier1 and jdk-tier2. The hs-tier3, hs-tier4 and hs-tier4 are in progress.


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