RFR: 8342540: InterfaceCalls micro-benchmark gives misleading results [v2]

[Aleksey Shipilev]

On Fri, 18 Oct 2024 16:18:02 GMT, Andrew Haley <aph at openjdk.org> wrote:

>> `InterfaceCalls.java` makes highly predictable memory accesses, which leads to a gross time underestimate of the case where a megamorphic access is unpredictable.
>> 
>> Here's one example, with and without randomization. The unpredictable megamorphic call takes more than 4* as long as the benchmark.
>> 
>> 
>> Benchmark                            (randomized)  Mode  Cnt   Score   Error  Units
>> InterfaceCalls.test2ndInt3Types             false  avgt    4   5.013 ± 0.081  ns/op
>> InterfaceCalls.test2ndInt3Types              true  avgt    4  23.421 ± 0.102  ns/op
>> ``` 
>> 
>> This patch adds the "randomized" parameter, which allows the measurement of predictable and unpredictable megamorphic calls.
>
> Andrew Haley has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Update test/micro/org/openjdk/bench/vm/compiler/InterfaceCalls.java
>   
>   Co-authored-by: Aleksey Shipilëv <shipilev at amazon.de>

Marked as reviewed by shade (Reviewer).

-------------

PR Review: https://git.openjdk.org/jdk/pull/21581#pullrequestreview-2382078512