RFR: 8352147: G1: TestEagerReclaimHumongousRegionsClearMarkBits test takes very long [v2]

[Thomas Schatzl]

> Hi all,
> 
>   please review this refactor of the TestEagerReclaimHumongousRegionsClearMarkBits test that runs way too long, and sometimes even causing timeouts in GHA.
> 
> So the problem is that TestEagerReclaimHumongousRegionsClearMarkBits checks whether after eager reclaim during marking the mark on the humongous object is cleared correctly. It does so with a trial-and-error approach allocating humongous objects and hoping that the faulty state somehow occurs.
> 
> This can take a long time, and although the test limits itself to 50s runtime, for some reason there can still be sporadic timeouts in some setups.
> 
> However for a long time it is possible to halt concurrent mark just before completion, inducing the exact state needed for this test. So rewrite the test to be more targeted.
> 
> Testing: gha, running test locally
> 
> Thanks,
>   Thomas

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

  * also check for actual region reclamation

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/24077/files
  - new: https://git.openjdk.org/jdk/pull/24077/files/8e834051..240f01f4

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=24077&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=24077&range=00-01

  Stats: 4 lines in 1 file changed: 4 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/24077.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24077/head:pull/24077

PR: https://git.openjdk.org/jdk/pull/24077