RFR: 8278756: Parallel: Drop PSOldGen::_reserved

[Thomas Schatzl]

On Tue, 14 Dec 2021 11:35:02 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

> Simple change of removing `PSOldGen::_reserved` and constructing reserved mem region on the fly.
> 
> Test: hotspot_gc, tier1-3

Looks good, but worried about the SA changes. Please confirm that tier4/5 are good.

src/hotspot/share/gc/parallel/vmStructs_parallelgc.hpp line 60:

> 58:   nonstatic_field(PSYoungGen,                  _max_gen_size,                                 const size_t)                          \
> 59:                                                                                                                                      \
> 60:   nonstatic_field(PSOldGen,                    _reserved,                                     MemRegion)                             \

Can you please test tier4/5 because of the removal of this `vmStructs` field to make sure that the SA agent still runs? The tests for it are in tier4 (or 5).

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Changes requested by tschatzl (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/6829