RFR: 8338977: Parallel: Improve heap resizing heuristics [v22]

[Albert Mingkun Yang]

On Tue, 16 Dec 2025 07:09:55 GMT, SilenceZheng66 <duke at openjdk.org> wrote:

> Since my JVM's version is 25.191-b12 ...

I thought it means JDK25... My apologies.

>  Now I just curious about is it a bug when people use configurations as following and could raise full GC problems and heap can't expand.

I think that behavior is definitely undesirable. Whether or not it's a bug can be subjective.

I believe this behavior has been fixed/improved in later releases of JDK. At least the following two tickets are relevant.

JDK-8328744: Parallel: Parallel GC throws OOM before heap is fully expanded
Use max old-gen capacity to decide whether to start a "proactive" full-gc, instead of young-gc.

JDK-8338977: Parallel: Improve heap resizing heuristics 
In `PSParallelCompact::summary_phase`, old-gen is expanded via `ParallelScavengeHeap::heap()->old_gen()->try_expand_till_size` even with `-XX:-UseAdaptiveSizePolicy`.

I wonder if you can try your benchmark(s) with newer JDKs and check if the problem persists.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25000#discussion_r2622829786