On Thu, 15 Oct 2026 21:29:19 GMT, Patrick Fontanilla <[email protected]> wrote:
>> ### Summary >> For Shenandoah and ZGC, safepoint workers were created at startup and only >> used for heap dump and heap inspection. If heap dump or heap inspection >> never runs, these threads consume memory without doing any work. For G1 and >> Parallel, GC pauses and non-GC safepoints share the GC worker pool, so heap >> dump and heap inspection don't need a separate worker pool. The downside is >> that dump and inspection work contributes to GC CPU time, which can affect >> how G1 sizes its heap. >> >> ### Changes >> Safepoint workers are replaced with a diagnostic worker pool used by heap >> dump and heap inspection. The diagnostic worker pool is created on the first >> heap dump or heap inspection that requests more than one thread, if the >> collector supports parallel heap iteration and >> `os::initial_active_processor_count()` > 1. The pool holds at most >> `os::initial_active_processor_count()` workers, and workers stay alive until >> the VM exits. >> >> G1 and Parallel no longer lend their GC worker pool. ZGC's `ZRuntimeWorkers` >> is deleted because it's no longer used. For Shenandoah, diagnostic workers >> have no GCLAB and fall back to shared allocation when they evacuate objects. >> >> ### Testing all passed >> - linux-x86_64-server-fastdebug: `hotspot:tier1_gc`, >> `hotspot:tier1_serviceability`, `gc/shenandoah` >> - GHA >> - Internal CI pipeline >> >> --------- >> - [x] I confirm that I make this contribution in accordance with the >> [OpenJDK Interim AI Policy](https://openjdk.org/legal/ai). > > Patrick Fontanilla has updated the pull request incrementally with one > additional commit since the last revision: > > Add comment to declaration of _workers OK. I forgot about the `parallel_object_iterator`. ------------- PR Comment: https://git.openjdk.org/jdk/pull/33218#issuecomment-6210209569
