8281168: Micro-optimize VarForm.getMemberName for interpreter

[shipilev]

I was looking for easy things to do to improve java.lang.invoke cold performance. One of the things is inlining VarForm.getMemberName a bit, so that interpreter does not have to call through getMemberNameOrNull.

There is direct VarHandle benchmark in our corpus:

$ CONF=linux-x86_64-server-release make run-test TEST=micro:java.lang.invoke.VarHandleExact MICRO="TIME=200ms;WARMUP_TIME=200ms;VM_OPTIONS=-Xint"

Benchmark                                 Mode  Cnt     Score    Error  Units

# -Xint
# Baseline
VarHandleExact.exact_exactInvocation      avgt   30   714.041 ±  5.882  ns/op
VarHandleExact.generic_exactInvocation    avgt   30   641.570 ± 11.681  ns/op
VarHandleExact.generic_genericInvocation  avgt   30  1336.571 ± 11.873  ns/op

# -Xint
# Patched
VarHandleExact.exact_exactInvocation      avgt   30   678.495 ± 10.752  ns/op ; +5%
VarHandleExact.generic_exactInvocation    avgt   30   573.320 ±  5.100  ns/op ; +11%
VarHandleExact.generic_genericInvocation  avgt   30  1338.593 ± 14.275  ns/op 

# (server, default)
# Baseline
VarHandleExact.exact_exactInvocation      avgt   30   0.620 ± 0.079  ns/op
VarHandleExact.generic_exactInvocation    avgt   30   0.602 ± 0.063  ns/op
VarHandleExact.generic_genericInvocation  avgt   30  10.521 ± 0.065  ns/op

# (server, default)
# Patched
VarHandleExact.exact_exactInvocation      avgt   30   0.621 ± 0.070  ns/op
VarHandleExact.generic_exactInvocation    avgt   30   0.601 ± 0.061  ns/op
VarHandleExact.generic_genericInvocation  avgt   30  10.499 ± 0.070  ns/op

Additional testing:

• Linux x86_64 fastdebug tier1
• Linux x86_64 fastdebug tier2
• Linux x86_64 fastdebug tier3

---

Progress

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Issue

• JDK-8281168: Micro-optimize VarForm.getMemberName for interpreter

Reviewers

• Claes Redestad (@cl4es - Reviewer) ⚠️ Review applies to 6202837
• Vladimir Ivanov (@iwanowww - Reviewer)
• Mandy Chung (@mlchung - Reviewer)

Reviewing

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[mlbridge]

Webrevs

• 01: Full - Incremental (a84a4e7e)
• 00: Full (62028379)

[cl4es]

Looks reasonable.

[openjdk]

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

8281168: Micro-optimize VarForm.getMemberName for interpreter

Reviewed-by: redestad, vlivanov, mchung

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At the time when this comment was updated there had been 44 new commits pushed to the master branch:

• 92f4f40: 8281104: jar --create should create missing parent directories
• 7f19c70: 8281061: [s390] JFR runs into assertions while validating interpreter frames
• 380378c: 8281400: Remove unused wcslen() function
• 83d6745: 8281450: Remove unnecessary operator new and delete from ObjectMonitor
• f5d8ceb: 8281296: Create a regression test for JDK-4515999
• 861f279: 8280917: Simplify G1ConcurrentRefineThread activation
• f2a9627: 8279329: Remove hardcoded IPv4 available policy on Windows
• 4eacacb: 8281314: Rename Stack{Red,Yellow,Reserved,Shadow}Pages multipliers
• 2f71a6b: 8279613: JFR: Snippify Javadoc
• 8a66210: 6779701: Wrong defect ID in the code of test LocalRMIServerSocketFactoryTest.java
• ... and 34 more: https://git.openjdk.java.net/jdk/compare/63a00a0df24b154ef459936dbd69bcd2f0626235...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.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

[shipilev]

Looks reasonable.

Thanks. Any more reviews needed, or I am pushing?

[cl4es]

Thanks. Any more reviews needed, or I am pushing?

I think you're good to push. I suspect some might question making the code ever so little less obvious/maintainable on behalf of interpreter performance, but I think it's well-motivated since startup speed is where MHs/VHs continue to feel a bit lackluster.

[iwanowww]

Thanks, looks good.

[mlchung]

This change looks okay. One biggest cold startup overhead we measured for JEP 416 is due to the overhead of spinning and loading classes of MH/VH. This micro-optimization focuses on the performance of VH invocation. Do you see class spinning and loading from your benchmark? Maybe in the generic invocation case?

[shipilev]

This change looks okay. One biggest cold startup overhead we measured for JEP 416 is due to the overhead of spinning and loading classes of MH/VH. This micro-optimization focuses on the performance of VH invocation. Do you see class spinning and loading from your benchmark? Maybe in the generic invocation case?

Not really, I am trying to see that -Xint does not have easy to fix impediments to cold performance. In this benchmark, bootstrapping stuff had already happened at warmup, it measures the overheads of doing all the MH/VH without the optimizing compiler assistance.

[shipilev]

/integrate

[openjdk]

Going to push as commit fc77217.
Since your change was applied there have been 50 commits pushed to the master branch:

• bce5dd1: 8280438: Improve BufferNode::Allocator::release to avoid walking pending list
• 13f739d: 8280830: Change NonblockingQueue::try_pop variable named "result"
• 2f46af0: 8280132: Incorrect comparator com.sun.beans.introspect.MethodInfo.MethodOrder
• fb17a8e: 8278947: Support for array constants in constant table
• d658d94: 8280828: Improve invariants in NonblockingQueue::append
• 5fb56db: 8281476: ProblemList tools/jar/CreateMissingParentDirectories.java
• 92f4f40: 8281104: jar --create should create missing parent directories
• 7f19c70: 8281061: [s390] JFR runs into assertions while validating interpreter frames
• 380378c: 8281400: Remove unused wcslen() function
• 83d6745: 8281450: Remove unnecessary operator new and delete from ObjectMonitor
• ... and 40 more: https://git.openjdk.java.net/jdk/compare/63a00a0df24b154ef459936dbd69bcd2f0626235...master

Your commit was automatically rebased without conflicts.

[openjdk]

@shipilev Pushed as commit fc77217.

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