RFR: 8291065: Creating a VarHandle for a static field triggers class initialization [v11]

[Chen Liang]

On Thu, 8 Jun 2023 01:32:20 GMT, Chen Liang <liach at openjdk.org> wrote:

>> 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 incrementally with one additional commit since the last revision:
> 
>   Remove meaningless target calls and clear outdated cache as needed

Will fix the indirect var handle NPE in a separate patch as recommended by Mandy.

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PR Comment: https://git.openjdk.org/jdk/pull/13821#issuecomment-1586604136