Hi, please review this change to generate classlists at build-time
bug: https://bugs.openjdk.java.net/browse/JDK-8150044 webrevs: top: http://cr.openjdk.java.net/~redestad/8150044/top.01/ jdk: http://cr.openjdk.java.net/~redestad/8150044/jdk.01/ hotspot: http://cr.openjdk.java.net/~redestad/8150044/hotspot.01/ The implementation generates an interim image consisting of a minimal set of modules, then use this to run a small generator program to load common utilities and facilities and dump the result of this to a classlist that is then bundled with the final images. The smaller number of classes on the default classlist (~1100 instead of ~2500) requires some adjustment to the metaspace defaults. This achieves the following: - Removes a manual, error-prone process to update the versioned classlists - Ensures the classlists shipped with the JDK/JRE is up to date with recent JDK changes, e.g., when moving classes from sun.* to jdk.internal.* - Automatically picks up and incorporates the output of jlink plugins such as GenerateJLIClassesPlugin into the classlist - Supports cross-compilation build targets, although it runs using a build JDK that can run on the host platform to generate such classlists (this isn't ideal, but no worse than the current situation, where the versioned classlist for the host platform is simply copied to the cross-compiled target) There are a few concerns/drawbacks: - It does add complexity to the build, and concern has been voiced that this would adversely affect build times. However, I'm happy to say that on my machine build times are roughly the same: Before: real 2m37.303s user 35m33.576s sys 3m46.476s After: real 2m36.168s user 35m31.232s sys 3m52.268s (real time varies ± 5s from build to build) - Startup on the specific applications we've used to generate the classlists for previously suffer small regressions. These are specifically rather dated AWT and Swing-based applications. OTOH, startup characteristics generally improve on other applications (minimal VM, jetty, etc...) Testing: JPRT -testset hotspot Thanks! /Claes