8368367: Test jdk/jfr/event/gc/detailed/TestGCHeapMemoryUsageEvent.java fails jdk.GCHeapMemoryUsage "expected 0 > 0"

[tschatzl]

Hi all,

please review this change to the TestGCHeapMemoryUsageEvent test that checks whether these kind of events are posted and contain some sensibles values.

In this failure, the used metric for the first of two events that is checked was zero. This is because G1, the default collector, updates the used value only at certain synchronization points to avoid inconsistencies in other cases. One of these synchronization points is region refill. With the 30gb heap in the test environment, region size is larger than what is allocated during startup, so no region refill/synchronization point has been reached yet, and used turns out to be 0.

This change fixes this by checking the last event instead of the first, it must have happened after that system.gc() call in the test, and used ought to be larger than zero because of allocations during VM startup.

An alternative could be limiting the test's heap size to something small, that would also help, but I thought this might need additional explanations.

Testing: local runs with G1 heap region size >= 16M or so do not fail any more.

Thanks,
Thomas

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Issue

• JDK-8368367: Test jdk/jfr/event/gc/detailed/TestGCHeapMemoryUsageEvent.java fails jdk.GCHeapMemoryUsage "expected 0 > 0" (Bug - P4)

Reviewers

• Ivan Walulya (@walulyai - Reviewer)
• Albert Mingkun Yang (@albertnetymk - Reviewer)
• SendaoYan (@sendaoYan - Committer)

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@tschatzl This change now passes all automated pre-integration checks.

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After integration, the commit message for the final commit will be:

8368367: Test jdk/jfr/event/gc/detailed/TestGCHeapMemoryUsageEvent.java fails  jdk.GCHeapMemoryUsage "expected 0 > 0"

Reviewed-by: iwalulya, ayang, syan

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At the time when this comment was updated there had been 14 new commits pushed to the master branch:

• 528f93f: 8367391: Loss of precision on implicit conversion in vectornode.cpp
• f36c33c: 8368152: Shenandoah: Incorrect behavior at end of degenerated cycle
• f68cba3: 8367611: Enable vblendvp[sd] on Future ECore
• ... and 11 more: https://git.openjdk.org/jdk/compare/29908148f819281dc6d1ef1274ca4d67a47754c0...master

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• 01: Full - Incremental (611551fd)
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[sendaoYan]

This fix works for me

[tschatzl]

Thanks @albertnetymk @sendaoYan @walulyai for your reviews
/integrate

[openjdk]

Going to push as commit ed31023.
Since your change was applied there have been 27 commits pushed to the master branch:

• f7c9fef: 8352069: Renamings after JEP 522: G1 GC: Improve Throughput by Reducing Synchronization
• 2a232d0: 8360979: Remove use of Thread.stop in krb5/auto/KDC.java
• 1cd186c: 8368331: ClassFile Signature parsing fails for type parameter with no supertype
• ... and 24 more: https://git.openjdk.org/jdk/compare/29908148f819281dc6d1ef1274ca4d67a47754c0...master

Your commit was automatically rebased without conflicts.

[openjdk]

@tschatzl Pushed as commit ed31023.

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