Greetings,

The following change set normalizes the ThreadGroup constants being serialized to the .jfr binary file.

It does this in two parts:

1. Re-inserts a scavenging scheme to remove stale (unloaded) ThreadGroups; some logic that we used to have in place, but may have been lost as part of the major refactoring around JFR Event Streaming, or even earlier. 2. Introduces a per-epoch "is_serialized" scheme, building on top of JFR epoch generations.

Problem manifestation is a very high number of duplicated TGs (jdk.types.ThreadGroup) as part of JFR checkpoints.

Testing: jdk_jfr

Thanks Markus

Markus Grönlund has updated the pull request incrementally with one additional commit since the last revision: adjustment ------------- Changes: - all: https://git.openjdk.org/jdk/pull/26558/files - new: https://git.openjdk.org/jdk/pull/26558/files/e973f67b..0691e4c5 Webrevs: - full: https://webrevs.openjdk.org/?repo=jdk&pr=26558&range=04 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=26558&range=03-04 Stats: 1 line in 1 file changed: 0 ins; 1 del; 0 mod Patch: https://git.openjdk.org/jdk/pull/26558.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/26558/head:pull/26558 PR: https://git.openjdk.org/jdk/pull/26558