On Tue, 18 Jun 2024 12:25:36 GMT, Axel Boldt-Christmas <abold...@openjdk.org> wrote:
> 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. This pull request has now been integrated. Changeset: 5909d541 Author: Axel Boldt-Christmas <abold...@openjdk.org> URL: https://git.openjdk.org/jdk/commit/5909d54147355dd7da5786ff39ead4c15816705c Stats: 80 lines in 6 files changed: 31 ins; 25 del; 24 mod 8326820: Metadata artificially kept alive Reviewed-by: eosterlund, stefank, coleenp ------------- PR: https://git.openjdk.org/jdk/pull/19769
