RFR: 8274178: G1: Occupancy value in IHOP logging and JFR event is inaccurate [v5]

[Thomas Schatzl]

> Hi all,
> 
>   please review this change that modifies heap occupancy reporting for IHOP to use the actual occupancy value the IHOP calculation actually uses.
> 
> I.e. previously IHOP logging used to report `G1CollectedHeap::used()` as occupancy (which is correct at a general level), but for IHOP/marking that value is not interesting, but the "occupancy" value used for comparing against the current heap occupancy threshold.
> 
> Testing: tier1-3, GHA
> 
> Thomas

Thomas Schatzl has updated the pull request incrementally with one additional commit since the last revision:

  * rename back `send_jfr_event`
  * rename `occupancy` to `non_young_occupancy`

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/28175/files
  - new: https://git.openjdk.org/jdk/pull/28175/files/15a720a9..c6e7e294

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=28175&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=28175&range=03-04

  Stats: 30 lines in 4 files changed: 0 ins; 0 del; 30 mod
  Patch: https://git.openjdk.org/jdk/pull/28175.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28175/head:pull/28175

PR: https://git.openjdk.org/jdk/pull/28175