8372412: Increase buffer size for ring-buffer events in CollectedHeap

[jsikstro]

Hello,

The buffer size we changed to when separating GC and Metaspace printing code is too small for Parallel and Serial (and maybe also for long-running programs in general). I suggest we bump the buffer-size to 1024 bytes. This also leaves room for more lengthy prints, which ZGC might have if running on a machine with many NUMA nodes.

The default number of events stored in each ring-buffer is 20, controlled via the diagnostic flag LogEventsBufferEntries. In it's default setting, the total memory usage of each ring-buffer (Metaspace and Heap) will increase from (512 bytes * 20) 10KB to (1024 * 20) 20KB.

For completeness, the content of the ring-buffers are only printed in hs_err files, using the -XX:+PrintVMInfoAtExit (diagnostic flag) or using jcmd VM.info

Testing:

• Local testing with java -XX:+UseParalellGC/UseSerialGC -XX:+PrintVMInfoAtExit ... to see that the message is not cut-off any longer.

---

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Issue

• JDK-8372412: Increase buffer size for ring-buffer events in CollectedHeap (Bug - P4)

Reviewers

• Stefan Karlsson (@stefank - Reviewer)
• Thomas Schatzl (@tschatzl - Reviewer)

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[openjdk]

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

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8372412: Increase buffer size for ring-buffer events in CollectedHeap

Reviewed-by: stefank, tschatzl

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At the time when this comment was updated there had been 7 new commits pushed to the master branch:

• 67b57f4: 8370978: Zero JVM fails to build on i386 after JDK-8351149
• f8cf9ca: 8370039: GenShen: array copy SATB barrier improvements
• a091af1: 8371475: HttpClient: Implement CUBIC congestion controller
• ... and 4 more: https://git.openjdk.org/jdk/compare/0c1ef366686b7ff1b461e2617f7f3b7a71467c04...master

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[jsikstro]

Thank you for the reviews! @stefank @tschatzl
/integrate

[openjdk]

Going to push as commit 81ea144.
Since your change was applied there have been 25 commits pushed to the master branch:

• d94c52c: 8367656: Refactor Constantpool's operand array into two
• c00d29a: 8372414: Command "make test-prebuilt" fails when listing tests
• 35f4a74: 8366888: C2: incorrect assertion predicate with short running long counted loop
• ... and 22 more: https://git.openjdk.org/jdk/compare/0c1ef366686b7ff1b461e2617f7f3b7a71467c04...master

Your commit was automatically rebased without conflicts.

[openjdk]

@jsikstro Pushed as commit 81ea144.

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