RFR: 8253877: gc/g1/TestGCLogMessages.java fails - missing "Evacuation failure" message

[Thomas Schatzl]

Hi all,

  can I have reviews for this change to gc/g1/TestGCLogMessages to hopefully make it more reliable?

One subtest tries to force evacuation failure, but apparently this does not always succeed. Particularly with upcoming
young gen sizing changes, there seems to be a larger than before chance that the current mechanism does not work.

This mechanism assumes that before that test the young gen has been sized that much that the allocation of a half-heap
humongous object causes an evacuation failure next time - of course that's a somewhat dodgy assumption that apparently
recently started failing more.

The change employs the G1 internal evacuation failure debugging mechanism to force this kind of situation. The
advantage is that this is guaranteed to work, the disadvantage is that it relies on that feature.

Additionally I did some slight renaming to the helper that used the term "ToSpaceExhaustion" instead of
"EvacuationFailure" which is the name of the message that is actually checked for.

Testing: 2k+ tests of previous version without reproduction (meaning that at least for me without context of other
tests, the issue has not been reproducable, at least not with the mentioned 1% failure rate), 3k tests with new version
without reproduction

Thanks,
  Thomas

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Commit messages:
 - Initial import

Changes: https://git.openjdk.java.net/jdk/pull/624/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=624&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8253877
  Stats: 18 lines in 1 file changed: 9 ins; 0 del; 9 mod
  Patch: https://git.openjdk.java.net/jdk/pull/624.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/624/head:pull/624

PR: https://git.openjdk.java.net/jdk/pull/624