RFR: 8246241: LambdaFormEditor should use a transform lookup key that is not a SoftReference

[Paul Sandoz]

Looks good. I sent some trivial comments offline.

Paul.

> On Jun 1, 2020, at 4:07 AM, Claes Redestad <claes.redestad at oracle.com> wrote:
> 
> Hi,
> 
> the LambdaFormEditor uses a SoftReference-based cache to avoid
> generating LambdaForms we have already generated. By introducing a
> lookup key that is not a SoftReference we can improve this by allocating
> less up front and by inducing less work for the GC later on.
> 
> I also refactored a few cases where I had neglected to add a static
> factory method to create the Transform (now TransformKey). For the
> transform types affected this helps further reduce allocations.
> 
> Bug:    https://bugs.openjdk.java.net/browse/JDK-8246241
> Webrev: http://cr.openjdk.java.net/~redestad/8246241/open.00/
> 
> Testing: tier1-2, java/lang/invoke locally with STRESS_TEST=true
> 
> Verified a speed-up on the micro added by JDK-8246152)[1], and
> on related startup tests[2].
> 
> Thanks!
> 
> /Claes
> 
> [1]
> Before (JDK-8246152):
> Benchmark Mode Cnt Score Error Units
> StringConcatFactoryBootstraps.makeConcatWithConstants avgt 10 2764.634 ± 56.244 ns/op
> StringConcatFactoryBootstraps.makeConcatWithConstants:·gc.alloc.rate.norm avgt 10 4136.187 ± 0.013 B/op
> 
> After:
> Benchmark                Mode  Cnt     Score     Error   Units
> StringConcatFactoryBootstraps.makeConcatWithConstants avgt 10 2299.919 ± 58.003 ns/op
> StringConcatFactoryBootstraps.makeConcatWithConstants:·gc.alloc.rate.norm avgt 10 3308.145 ± 6.378 B/op
> 
> [2] http://cr.openjdk.java.net/~redestad/scratch/erase_scf_types.00/ObjStringCombos.java
> 
> Before (JDK-8246152):
>     3,485,679,714      instructions              #    1.09  insn per cycle           ( +-  0.90% )
>       692,247,529      branches                  #  491.822 M/sec          ( +-  0.92% )
>        28,939,534      branch-misses             #    4.18% of all branches          ( +-  0.90% )
> 
>       0.291642667 seconds time elapsed          ( +-  0.93% )
> 
> After:
>     3,411,619,586      instructions              #    1.09  insn per cycle           ( +-  0.63% )
>       677,767,258      branches                  #  493.911 M/sec               ( +-  0.64% )
>        28,337,022      branch-misses             #    4.18% of all branches          ( +-  0.63% )
> 
>       0.288959534 seconds time elapsed          ( +-  0.86% )