RFR: 8291065: Creating a VarHandle for a static field triggers class initialization [v12]
Chen Liang
liach at openjdk.org
Tue Jun 27 03:43:47 UTC 2023
> Also fixed the bug with NPE in `IndirectVarHandle::isAccessModeSupported`.
>
> A few implementation-detail methods in VarHandle are now documented with the implied constraints to avoid subtle problems in the future. Changed `IndirectVarHandle` to call `asDirect` lazily to accomodate the lazy VarHandle changes. Also changed VarHandleBaseTest to report the whole incorrect type of exception caught than swallow it and leaving only a message.
>
> Current problems:
> - [ ] The lazy var handle is quite slow on the first invocation.
> - As seen in the benchmark, users can first call `Lookup::ensureInitialized` to create an eager handle.
> - After that, the lazy handle has a performance on par with the regular var handle.
> - [ ] The class-loading-based test is not in a unit test
> - The test frameworks don't seem to offer fine-grained control for class-loading detection or reliable unloading
>
>
> Benchmark Mode Cnt Score Error Units
> VarHandleLazyStaticInvocation.initializedInvocation avgt 30 0.817 ± 0.012 ns/op
> VarHandleLazyStaticInvocation.lazyInvocation avgt 30 0.805 ± 0.007 ns/op
>
>
> Benchmark Mode Cnt Score Error Units
> Benchmark Mode Cnt Score Error Units
> LazyStaticColdStart.methodHandleCreateEager ss 10 36.890 ± 2.891 us/op
> LazyStaticColdStart.methodHandleCreateLazy ss 10 18.340 ± 1.537 us/op
> LazyStaticColdStart.methodHandleInitializeCallEager ss 10 50.000 ± 5.590 us/op
> LazyStaticColdStart.methodHandleInitializeCallLazy ss 10 90.550 ± 10.142 us/op
> LazyStaticColdStart.varHandleCreateEager ss 10 36.610 ± 2.685 us/op
> LazyStaticColdStart.varHandleCreateLazy ss 10 18.200 ± 1.811 us/op
> LazyStaticColdStart.varHandleInitializeCallEager ss 10 71.680 ± 11.097 us/op
> LazyStaticColdStart.varHandleInitializeCallLazy ss 10 72.090 ± 4.494 us/op
Chen Liang has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 25 commits:
- Fix bugs
- Merge branch 'master' into lazy-static-varhandle
- Move initialization barrier to getMethodHandle(Uncached)
- Merge branch 'master' into lazy-static-varhandle
- Remove meaningless target calls and clear outdated cache as needed
- Split ensureInitialized
- Merge branch 'master' into lazy-static-varhandle
- Significantly improve Lazy VH initial call performance
- Rename asDirect to target
- Merge branch 'master' into lazy-static-varhandle
- ... and 15 more: https://git.openjdk.org/jdk/compare/87e6fab2...0ac094b8
-------------
Changes: https://git.openjdk.org/jdk/pull/13821/files
Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13821&range=11
Stats: 789 lines in 11 files changed: 613 ins; 16 del; 160 mod
Patch: https://git.openjdk.org/jdk/pull/13821.diff
Fetch: git fetch https://git.openjdk.org/jdk.git pull/13821/head:pull/13821
PR: https://git.openjdk.org/jdk/pull/13821
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