8297692: Avoid sending per-region GCPhaseParallel JFR events in G1ScanCollectionSetRegionClosure

[tschatzl]

Hi all,

please review this change that significantly reduces the amount of "Code Roots" and "Optional Roots" JFR events to reduce default recording sizes significantly.

E.g. a 10min BigRamTester run creates a 23MB recording without this change, with like hundreds of thousands of these events (#gcs * #gc threads * #regions in collection set). With this change, the recording is reduced to 4MB (#gcs * #gc threads)

Testing: gha, tier1-3

Thanks,
Thomas

---

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Issue

• JDK-8297692: Avoid sending per-region GCPhaseParallel JFR events in G1ScanCollectionSetRegionClosure (Enhancement - P4)

Reviewers

• Ivan Walulya (@walulyai - Reviewer)
• Albert Mingkun Yang (@albertnetymk - Reviewer)
• Sangheon Kim (@sangheon - Reviewer)

Reviewing

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[openjdk]

@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:

8297692: Avoid sending per-region GCPhaseParallel JFR events in G1ScanCollectionSetRegionClosure

Reviewed-by: iwalulya, ayang, sangheki

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At the time when this comment was updated there had been 87 new commits pushed to the master branch:

• 90e9234: 8344074: RISC-V: C1: More accurate _exception_handler_size and _deopt_handler_size
• 3b28354: 8339288: Improve diagnostic logging runtime/cds/DeterministicDump.java
• 0dab920: 8343984: Fix Unsafe address overflow
• 168b18e: 8343958: Remove security manager impl in java.lang.Process and java.lang.Runtime.exec
• 5ac330b: 8344039: Remove security manager dependency in java.time
• 1eb38c8: 8343219: Manual clientlibs test failures after SM removal
• dde6230: 8343416: CDS dump fails when unregistered class can also be loaded from system modules
• ffea980: 8344023: Unnecessary Hashtable usage in LdapClient.defaultBinaryAttrs
• 5e01c40: 8343981: Remove usage of security manager from Thread and related classes
• dbf2346: 8341260: Add Float16 to jdk.incubator.vector
• ... and 77 more: https://git.openjdk.org/jdk/compare/0c281acfb4c87436096cb562d70f800dffa3671a...master

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[openjdk]

@tschatzl The following label will be automatically applied to this pull request:

• hotspot-gc

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[mlbridge]

Webrevs

• 00: Full (af42bec9)

[tschatzl]

Fwiw, I went with splitting code root scan and optional root scan into two iterations that are each bracketed by a single per-thread JFR event now.
This also allowed a minor optimization: in the initial evacuation there can be no optional roots, so that iteration over all regions can be skipped.

[walulyai]

LGTM!

[sangheon]

LGTM

[tschatzl]

Thanks @sangheon @walulyai @albertnetymk for your reviews

/integrate

[openjdk]

Going to push as commit a73226b.
Since your change was applied there have been 105 commits pushed to the master branch:

• 6e28cd3: 8343488: Test VectorRebracket128Test.java can't exclude by test/hotspot/jtreg/ProblemList.txt
• 6757994: 8343633: The ClassLoader::print_counters() prints to stdout when logging is enabled.
• 8ccc48c: 8344032: InterpreterRuntime::verify_mdp() missing lock while printing MethodData on failure
• 2145ace: 8341094: Clean up relax_verify in ClassFileParser
• 5731ab7: 8335991: Implement Simple Source Files and Instance Main Methods (Fourth Preview)
• 81342ac: 8343752: The javadoc should contain a note about usages of requires transitive java.base;
• 8523880: 8342693: Use byte[] as parameter in a FDBigInteger constructor and as field
• 2b57f40: 8343426: ConcurrentSkipListMap.spliterator() can no longer split the stream
• a8152bd: 8343941: IGV: dump graph at different register allocation steps
• bd6152f: 8343855: HTTP/2 ConnectionWindowUpdateSender may miss some unprocessed DataFrames from closed streams
• ... and 95 more: https://git.openjdk.org/jdk/compare/0c281acfb4c87436096cb562d70f800dffa3671a...master

Your commit was automatically rebased without conflicts.

[openjdk]

@tschatzl Pushed as commit a73226b.

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