RFR: 8325134: Serial: Remove Generation::used_region

[Thomas Schatzl]

On Thu, 1 Feb 2024 15:44:40 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

> Trivial removing dead code. The change of moving the definition to `tenuredGeneration.hpp` is needed to work around linking failure.

Changes requested by tschatzl (Reviewer).

src/hotspot/share/gc/serial/tenuredGeneration.hpp line 96:

> 94:   size_t free() const;
> 95: 
> 96:   MemRegion used_region() const { return space()->used_region(); }

This move requires inclusion of `space.hpp`.

Maybe it is better to move `save_used_region()` into the `.inline.hpp` file as well and include the `.inline.hpp` file where needed.

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PR Review: https://git.openjdk.org/jdk/pull/17673#pullrequestreview-1856894012
PR Review Comment: https://git.openjdk.org/jdk/pull/17673#discussion_r1474717076