RFR: 8349213: G1: Clearing bitmaps during collection set merging not claimed by region

[Albert Mingkun Yang]

On Mon, 3 Feb 2025 14:11:20 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

> Hi all,
> 
>   please review this change that makes (optional) bitmap clearing during merging remembered sets claim regions. Otherwise every thread will do the (currently little) work themselves over and over again.
> 
> Testing: tier1-3
> 
> Thanks,
>   Thomas

src/hotspot/share/gc/g1/g1RemSet.cpp line 1390:

> 1388:         g1h->collection_set_iterate_increment_from(&merge, worker_id);
> 1389:         for (uint i = 0; i < G1GCPhaseTimes::MergeRSContainersSentinel; i++) {
> 1390:           p->record_or_add_thread_work_item(merge_remset_phase, worker_id, merge.stats().merged(i), i);

`stats()` has side-effect; should be invoked only once.

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PR Review Comment: https://git.openjdk.org/jdk/pull/23419#discussion_r1940791948