RFR: 8342382: Implement JEP 522: G1 GC: Improve Throughput by Reducing Synchronization [v54]

[Emanuel Peter]

On Wed, 10 Sep 2025 08:19:15 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

>> test/hotspot/jtreg/testlibrary_tests/ir_framework/tests/TestIRMatching.java line 1489:
>> 
>>> 1487:     @Test
>>> 1488:     @IR(failOn = IRNode.ALLOC)
>>> 1489:     @IR(counts = {IRNode.COUNTED_LOOP, ">1"}) // not fail
>> 
>> Can you explain what led to the difference? Can you also set an upper bound?
>
> With the decreased complexity of the barrier, C2 started unrolling that loop. I do not know how to determine a bound here.

Is this going to be GC independent? What if the VM swaps to another GC ergonomically?

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PR Review Comment: https://git.openjdk.org/jdk/pull/23739#discussion_r2335985122