RFR JDK-8234049: Implementation of Memory Access API (Incubator)

[Maurizio Cimadamore]

On 05/12/2019 23:27, Maurizio Cimadamore wrote:
> This gives same performance as with -XX:+TrustFinalNonStaticFields - 
> if we remove these changes, then memory segment bounds are never 
> inlined. I'm happy to change this if you have other suggestions on how 
> to get there, of course (I can run some benchmarks w/ and w/o and post 
> some numbers if that helps). 

Here are some numbers for a straight VH get using a constant address; 
with the patch I get this (throughput - higher the better):

GetSetConstantBenchmark.testMemoryHandleGet  --> 299325598.056 ± 
160635.595  ops/s

Without the patch I get this:

GetSetConstantBenchmark.testMemoryHandleGet  -->  163721200.469 ± 
2344351.046  ops/s


So, the difference is quiet big. Graal (using JVMCI) seems less 
sensitive to this particular issue, and I detected no differences there.

That said, if we have plans to fix this another way, I'm happy to remove 
this workaround.

Cheers
Maurizio