RFR: 8338977: Parallel: Improve heap resizing heuristics [v3]

[Zhengyu Gu]

On Mon, 19 May 2025 11:05:59 GMT, Guoxiong Li <gli at openjdk.org> wrote:

>> The one inside the safepoint will print sth `log_info(gc)("GCOverheadLimitThreshold ...`. There can be multiple concurrent mutators reaching here; printing here is undesirable.
>> 
>> I don't think throwing OOM, from gc's perspective, is an "error".
>
>> I don't think throwing OOM, from gc's perspective, is an "error".
> 
> Nevermind; I just obey the statement in methods `MemAllocator::Allocation::check_out_of_memory` and `Universe::out_of_memory_error_java_heap`.

Returning `null` outside of a safe point does have unexpected negative effects. e.g. `HeapDumpOnOutOfMemoryError` may not get good heap dump, as other threads can come in and run additional GCs, then the heap dump may contain confusingly little live data.

I wonder if you can improve this situtation.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25000#discussion_r2181262727