RFR: 8367993: G1: Speed up ConcurrentMark initialization [v3]

[Leo Korinth]

On Mon, 12 Jan 2026 13:32:35 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

>> src/hotspot/share/gc/g1/g1Policy.cpp line 744:
>> 
>>> 742:   if (!_g1h->concurrent_mark()->is_fully_initialized()) {
>>> 743:     return false;
>>> 744:   }
>> 
>> Is this needed? The `in_progress()` check below makes sure to only check the cm_thread when fully initialized.
>
> And this can never return true during initialization as no GC can have happened so that we end up in the Prepare Mixed GC

I removed it, and it seems to work.

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PR Review Comment: https://git.openjdk.org/jdk/pull/28723#discussion_r2716695044