> ClassLoaderDataGraph provides APIs for walking different metadata. All the > iterators which are not designed to be used by the GC also keep the holder of > the CLDs alive and by extensions keeps all metadata alive. This is > problematic for concurrent GC as it keeps otherwise unreachable classes from > being unloaded and the respective metadata freed. > > This patch changes the default iteration behaviour to not keep the holder > alive, with the exception of `loaded_classes_do` (renamed > `loaded_classes_do_keepalive`) and `modules_do` (renamed > `modules_do_keepalive`) which is used by jvmti APIs that requires that the > holder is kept alive. > > All other uses consumes all the metadata it queries during its safepoint or > before releasing the `ClassLoaderDataGraph_lock`. > > Before this change some jcmd, new jfr chunks and some jfr events, all of > which consumed these APIs, could cause class unloading to not occur. > > Been running our internal stress test in an even more stressful mode which > without this patch reproduces the metaspace OOME > [JDK-8326005](https://bugs.openjdk.org/browse/JDK-8326005) consistently > within a few hours. And after this patch it does not. > > Currently running tier1-tier8 testing.
Axel Boldt-Christmas has updated the pull request incrementally with one additional commit since the last revision: Document the iterator and functions ------------- Changes: - all: https://git.openjdk.org/jdk/pull/19769/files - new: https://git.openjdk.org/jdk/pull/19769/files/08366b12..0048f8bd Webrevs: - full: https://webrevs.openjdk.org/?repo=jdk&pr=19769&range=01 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=19769&range=00-01 Stats: 28 lines in 2 files changed: 12 ins; 0 del; 16 mod Patch: https://git.openjdk.org/jdk/pull/19769.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/19769/head:pull/19769 PR: https://git.openjdk.org/jdk/pull/19769
