I wonder how things would have stacked with OpenJ9 - AdoptOpenJDK project makes OpenJ9 builds available for Java 8/11/13/14 - so it should be trivial to include it in the benchmarks.
We have been experimenting with it in light of the Oracle licensing situation and it does provide interesting set of options - AOT, various GCs (metronome, gencon, balanced) along with many other differentiators to OpenJDK like JITServer which offloads JIT compilation to remote nodes.
It doesn't get as much coverage when it should - it's production hardened - IBM has used it and still uses it for all their products - and it's fully open source.
We have been experimenting with it in light of the Oracle licensing situation and it does provide interesting set of options - AOT, various GCs (metronome, gencon, balanced) along with many other differentiators to OpenJDK like JITServer which offloads JIT compilation to remote nodes.
https://www.eclipse.org/openj9/docs/gc/
It doesn't get as much coverage when it should - it's production hardened - IBM has used it and still uses it for all their products - and it's fully open source.