8280784: VM_Cleanup unnecessarily processes all thread oops

[stefank]

While looking at ZGC latencies in a benchmark with >20000 Java threads, I noticed that the Cleanup VM operation could take up to 500 ms. It turned out that the time was spent processing the oops in all Java threads. Since none of the safepoint cleanup tasks use the oops in the threads, I propose that we stop processing the oops in this VM Operation.

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Issue

• JDK-8280784: VM_Cleanup unnecessarily processes all thread oops

Reviewers

• Erik Österlund (@fisk - Reviewer)
• Aleksey Shipilev (@shipilev - Reviewer)

Reviewing

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[stefank]

/label add hotspot

[stefank]

Tested with Oracle tier1-3

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[openjdk]

@stefank
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[mlbridge]

Webrevs

• 00: Full (31f9a04f)

[fisk]

Looks good.

[openjdk]

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

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8280784: VM_Cleanup unnecessarily processes all thread oops

Reviewed-by: eosterlund, shade

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At the time when this comment was updated there had been 3 new commits pushed to the master branch:

• cab5905: 8280583: Always build NMT
• 7f68759: 8280719: G1: Remove outdated comment in RemoveSelfForwardPtrObjClosure::apply
• 94380d0: 8278232: [macos] Wrong chars emitted when entering certain char-sequence of Indic language

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[shipilev]

Looks fine, but doesn't that apply to other "empty" VMOps: VM_None, VM_ForceSafepoint, VM_ThreadSuspend, etc? Probably some code commoning is in order there...

[stefank]

@shipilev Yeah, probably. None of the listed VM operations seemed time-sensitive to me, so I left them as-is. But I'll try to unify this and re-run the tests.

[shipilev]

@shipilev Yeah, probably. None of the listed VM operations seemed time-sensitive to me, so I left them as-is. But I'll try to unify this and re-run the tests.

No need to do the unification here, I think. This point change is cleanly backportable. Unification in some future RFR would be nice.

[stefank]

/integrate

[openjdk]

Going to push as commit 8a3cca0.
Since your change was applied there have been 14 commits pushed to the master branch:

• 973dda5: 8280804: Parallel: Remove unused variables in PSPromotionManager::drain_stacks_depth
• 55f180f: 8280004: DCmdArgument::parse_value() should handle NULL input
• 178ac74: 8251466: test/java/io/File/GetXSpace.java fails on Windows with mapped network drives.
• a1d1e47: 8280823: Remove NULL check in DumpTimeClassInfo::is_excluded
• 094db1a: 8277948: AArch64: Print the correct native stack if -XX:+PreserveFramePointer when crash
• 7857405: 8280744: Allow SuppressWarnings to be used in all declaration contexts
• 40a2ce2: 8270476: Make floating-point test infrastructure more lambda and method reference friendly
• 6d242e4: 8280835: jdk/javadoc/tool/CheckManPageOptions.java depends on source hierarchy
• ece89c6: 8280366: (fs) Restore Files.createTempFile javadoc
• b94ebaa: 8280686: Remove Compile::print_method_impl
• ... and 4 more: https://git.openjdk.java.net/jdk/compare/0dba1707910734d03c318424764b8682b028a8e0...master

Your commit was automatically rebased without conflicts.

[openjdk]

@stefank Pushed as commit 8a3cca0.

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