8270321: Startup regressions in 18-b5 caused by JDK-8266310

[sercher]

Dear colleagues,

Please review the patch that replaces the lambdas with anonymous classes which solves the startup time regression as shown below.

I attached the Bytestacks flamegraphs for both original (regression) and fixed versions. The flamegraphs clearly show the lambdas were causing the performance issue.

bytestacks_flamegraphs.zip

Although the proposed JDK-8270321 patch fixes the startup time (it might appear even better than it was before the regression was introduced, i.e. before JDK-8266310) and generally fixes the footprint regression, it may increase MaxRSS slightly compared to the version before JDK-8266310, which is shown in the below graphs. (updated)

(update: added ZGC graphs)

I additionally include the heap objects histograms to show the change does not increase the total live objects size significantly with only 1000 bytes the total difference, namely 1116128 bytes in 25002 live objects after the proposed fix JDK-8270321 compared to 1115128 bytes in 24990 objects in the version with the original patch reverted (i.e. before JDK-8266310).

histograms.zip

The patch was tested w/hotspot/tier1/tier2 test groups.

---

Progress

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Issue

• JDK-8270321: Startup regressions in 18-b5 caused by JDK-8266310

Reviewers

• Mandy Chung (@mlchung - Reviewer)
• Alan Bateman (@AlanBateman - Reviewer)

Reviewing

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Update a local copy of the PR:
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$ git pull https://git.openjdk.java.net/jdk pull/4893/head

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$ git pr checkout 4893

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https://git.openjdk.java.net/jdk/pull/4893.diff

[bridgekeeper]

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[openjdk]

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[mlbridge]

Webrevs

• 00: Full (6940aac0)

[forax]

I don't understand your analysis, you are testing the startup time with -Xint which disable JITs, but there is no mention of -Xint in the bug report.
It's obvious to me that there is a regression with -Xint given that the lambda creation is using invokedynamic which is only optimizable by JITs.

I think you should first try to reproduce the issue with the correct flags and then follow the advice from Mandy on how to implement the fix. Using an anonymous class may introduce more allocation than using a lambda once the code is JITed.

[sercher]

Hi Rémi,

I don't understand your analysis, you are testing the startup time with -Xint which disable JITs, but there is no mention of -Xint in the bug report.
It's obvious to me that there is a regression with -Xint given that the lambda creation is using invokedynamic which is only optimizable by JITs.

I apologize, perhaps I wasn't quite clear describing the analysis. Also, there was a faulty picture, -Xint was only used to grab the opcode traces to build the flamegraphs. I replaced the faulty image and posted additional graphs with -XX:+UseZGC.
Performance (startup) testing, as well as the live objects dumps were obtained with JIT enabled and with G1GC and ZGC. Would you think more data is needed with -Xint? (in addition to the flamegraphs which are obtained with -Xint)

I think you should first try to reproduce the issue with the correct flags and then follow the advice from Mandy on how to implement the fix.

In my opinion removing computeXXX methods defeats the purpose of the entire deadlock fix. It is sufficient to avoid using lambdas in order not to trigger the method handles initialization, which is what Mandy Chung is really suggesting in the first note in JBS.

Using an anonymous class may introduce more allocation than using a lambda once the code is JITed.

I provided live objects dumps after noop.jar has been loaded with JIT enabled. Please see the attached histograms. The difference is always the same after full GC (1000 bytes in 12 objects compared to pre JDK-8266310 version tested w/G1) and it doesn't change with subsequent executions. The patch resolves the memory regression as you may observe in RSS graphs and heap dumps. Please see 'fixed.histogram' in comparison with the object dump before the fix (post JDK-8266310) in 'original.histogram'.

[AlanBateman]

I don't understand your analysis, you are testing the startup time with -Xint which disable JITs, but there is no mention of -Xint in the bug report.
It's obvious to me that there is a regression with -Xint given that the lambda creation is using invokedynamic which is only optimizable by JITs.

Eric Caspole (the submitter) may be able to share more data but the startup regression looks plausible given that this code executes early in the startup.

[mlchung]

NativeLibraries was called early during VM startup and the startup benchmark is just a Noop. So the lambda creation by NativeLibraries is likely still running in interpreted mode.

Looks like replacing it with an anonymous class may be an alternative. I ran a few startup benchmarks on linux x64 with this patch. It does show that the startup regression is fixed and also the footprint benchmark I included does not show any regression.

[forax]

Hi Sergey,
thanks for the explanation, i don't think there is a need for more data with -Xint.

Using anonymous classes instead of lambdas is good for me.

[openjdk]

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

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

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

8270321: Startup regressions in 18-b5 caused by JDK-8266310

Reviewed-by: mchung, alanb

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 72 new commits pushed to the master branch:

• 89f5c96: 8232066: Remove outdated code/methods from PKIX implementation
• 9856ace: 8268963: [IR Framework] Some default regexes matching on PrintOptoAssembly in IRNode.java do not work on all platforms
• b59418f: 8270060: (jdeprscan) tools/jdeprscan/tests/jdk/jdeprscan/TestRelease.java failed with class file for jdk.internal.util.random.RandomSupport not found
• 4f42eb6: 8269523: runtime/Safepoint/TestAbortOnVMOperationTimeout.java failed when expecting 'VM operation took too long'
• 77fbd99: 8270341: Test serviceability/dcmd/gc/HeapDumpAllTest.java timed-out
• 048fb2c: Merge
• 286d313: 8271489: (doc) Clarify Filter Factory example
• d09b028: 8271396: Spelling errors
• 489e5fd: 8268019: C2: assert(no_dead_loop) failed: dead loop detected
• 6afcf5f: 8270886: Crash in PhaseIdealLoop::verify_strip_mined_scheduling
• ... and 62 more: https://git.openjdk.java.net/jdk/compare/ec71e2d891fdb9b102ce232f65cfcc5c6a1a9580...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

As you do not have Committer status in this project an existing Committer must agree to sponsor your change. Possible candidates are the reviewers of this PR (@mlchung, @AlanBateman) but any other Committer may sponsor as well.

➡️ To flag this PR as ready for integration with the above commit message, type /integrate in a new comment. (Afterwards, your sponsor types /sponsor in a new comment to perform the integration).

[voitylov]

Thanks Sergey for dealing with this while I was on vacation, and sorry for causing this regression! Looks good (not a reviewer).

[sercher]

/integrate

[openjdk]

@sercher
Your change (at version 6940aac) is now ready to be sponsored by a Committer.

[AlexanderScherbatiy]

/sponsor

[openjdk]

Going to push as commit 5b3c418.
Since your change was applied there have been 73 commits pushed to the master branch:

• baf7797: 8049301: Suspicious use of string identity checks in JComponent.setUIProperty
• 89f5c96: 8232066: Remove outdated code/methods from PKIX implementation
• 9856ace: 8268963: [IR Framework] Some default regexes matching on PrintOptoAssembly in IRNode.java do not work on all platforms
• b59418f: 8270060: (jdeprscan) tools/jdeprscan/tests/jdk/jdeprscan/TestRelease.java failed with class file for jdk.internal.util.random.RandomSupport not found
• 4f42eb6: 8269523: runtime/Safepoint/TestAbortOnVMOperationTimeout.java failed when expecting 'VM operation took too long'
• 77fbd99: 8270341: Test serviceability/dcmd/gc/HeapDumpAllTest.java timed-out
• 048fb2c: Merge
• 286d313: 8271489: (doc) Clarify Filter Factory example
• d09b028: 8271396: Spelling errors
• 489e5fd: 8268019: C2: assert(no_dead_loop) failed: dead loop detected
• ... and 63 more: https://git.openjdk.java.net/jdk/compare/ec71e2d891fdb9b102ce232f65cfcc5c6a1a9580...master

Your commit was automatically rebased without conflicts.

[openjdk]

@AlexanderScherbatiy @sercher Pushed as commit 5b3c418.

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