RFR: 8351565: Implement JEP 502: Stable Values (Preview) [v21]

[Per Minborg]

On Mon, 31 Mar 2025 15:15:31 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

> > Here are the latest benchmarks run on an M1 (macOS):
> > ```
> > Benchmark                                           Mode  Cnt  Score   Error  Units
> > StableFunctionBenchmark.function                    avgt   10  4.228 ? 0.172  ns/op
> > StableFunctionBenchmark.map                         avgt   10  4.323 ? 0.289  ns/op
> > StableFunctionBenchmark.staticIntFunction           avgt   10  1.724 ? 0.121  ns/op
> > StableFunctionBenchmark.staticSMap                  avgt   10  1.710 ? 0.045  ns/op
> > StableFunctionSingleBenchmark.function              avgt   10  4.329 ? 0.184  ns/op
> > StableFunctionSingleBenchmark.map                   avgt   10  4.291 ? 0.142  ns/op
> > StableFunctionSingleBenchmark.staticIntFunction     avgt   10  0.704 ? 0.022  ns/op
> > StableFunctionSingleBenchmark.staticSMap            avgt   10  0.708 ? 0.027  ns/op
> > StableIntFunctionBenchmark.intFunction              avgt   10  1.558 ? 0.063  ns/op
> > StableIntFunctionBenchmark.list                     avgt   10  1.579 ? 0.141  ns/op
> > StableIntFunctionBenchmark.staticIntFunction        avgt   10  1.044 ? 0.031  ns/op
> > StableIntFunctionBenchmark.staticList               avgt   10  2.280 ? 2.013  ns/op
> > StableIntFunctionSingleBenchmark.intFunction        avgt   10  2.333 ? 0.033  ns/op
> > StableIntFunctionSingleBenchmark.list               avgt   10  2.335 ? 0.046  ns/op
> > StableIntFunctionSingleBenchmark.staticIntFunction  avgt   10  0.670 ? 0.022  ns/op
> > StableIntFunctionSingleBenchmark.staticList         avgt   10  0.679 ? 0.021  ns/op
> > StableSupplierBenchmark.stable                      avgt   10  1.377 ? 0.042  ns/op
> > StableSupplierBenchmark.staticStable                avgt   10  0.362 ? 0.077  ns/op
> > StableSupplierBenchmark.staticSupplier              avgt   10  0.338 ? 0.016  ns/op
> > StableSupplierBenchmark.supplier                    avgt   10  1.609 ? 0.042  ns/op
> > StableValueBenchmark.atomic                         avgt   10  1.357 ? 0.046  ns/op
> > StableValueBenchmark.dcl                            avgt   10  1.369 ? 0.058  ns/op
> > StableValueBenchmark.refSupplier                    avgt   10  0.442 ? 0.007  ns/op
> > StableValueBenchmark.stable                         avgt   10  1.522 ? 0.267  ns/op
> > StableValueBenchmark.stableNull                     avgt   10  1.237 ? 0.117  ns/op
> > StableValueBenchmark.staticAtomic                   avgt   10  1.220 ? 0.058  ns/op
> > StableValueBenchmark.staticDcl                      avgt   10  0.357 ? 0.022  ns/op
> > StableValueBenchmark.staticHolder                   avgt   10  1.452 ? 0.205  ns/op
> > StableValueBenchmark.staticRecordHolder             avgt   10  0.367 ? 0.028  ns/op
> > StableValueBenchmark.staticStable                   avgt   10  0.365 ? 0.026  ns/op
> > Finished running test 'micro:java.lang.stable'
> > ```
> 
> This seems an outlier:
> 
> ```
> StableIntFunctionBenchmark.staticList               avgt   10  2.280 ? 2.013  ns/op
> ```
> 
> (I also note the high error)
> 
> I believe it could be useful to have one more benchmark showing a `StableValue` holding a `MethodHandle` and do a `get()` + `invokeExact`. I believe that should report more dramatic distinctions when compared to atomic/dcl?

Thanks for "hawk-eying" this discrepancy. There seemed to be some flux when I ran the benchmarks (I've used a laptop). Running the benchmarks in a more controlled environment revealed there was no difference. Also, rerunning the particular benchmark now shows:


StableIntFunctionBenchmark.intFunction         avgt   10  2.317 ? 1.252  ns/op
StableIntFunctionBenchmark.list                avgt   10  2.303 ? 1.302  ns/op
StableIntFunctionBenchmark.staticIntFunction   avgt   10  1.044 ? 0.036  ns/op
StableIntFunctionBenchmark.staticList          avgt   10  1.052 ? 0.061  ns/op


I will add a `MethodHandle` benchmark. Good suggestion!

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PR Comment: https://git.openjdk.org/jdk/pull/23972#issuecomment-2766618937