RFR: 8336463: Parallel: Add PSOldGen::expand_and_allocate

[Zhengyu Gu]

On Tue, 16 Jul 2024 10:00:35 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

> Simple adding an API to old-gen to support calls by VM thread in safepoint.
> 
> Test: tier1-3

src/hotspot/share/gc/parallel/psOldGen.cpp line 129:

> 127:     expand(word_size*HeapWordSize);
> 128:   }
> 129:   return cas_allocate_noexpand(word_size);

This implies a race and `cas_allocate_noexpand()` can fail prematurely due to the race. Is it an acceptable case?

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PR Review Comment: https://git.openjdk.org/jdk/pull/20189#discussion_r1679349561