Note that you aren't tied to Java 8, which is quite old by now, but can also run GraalJS with OpenJDK 11, 12, 13, and enjoy the recent performance improvements to the GC (using ZGC or Shenandoah) and startup time (using Application CDS):
So is graal polyglot already compatible with newer JDKs and it's just native image generation that's blocking the upgrade? https://github.com/oracle/graal/issues/651
We are working with a very high priority on JDK 11 support. We should be able to ship it in a few months from now.
> So is graal polyglot already compatible with newer JDKs and it's just native image generation that's blocking the upgrade?
Not just. We also need to upgrade the JVMCI version we use in order to support libgraal (Graal compiler as native-image in HotSpot). Also, modules make everything a little bit more complicated as well.