32% performance increase with Oracle JDK 8 over OpenJDK 7. I pity projects tied to this modern day Cobol that have to deal with this crap. Write once, run anywhere (badly, unless Oracle likes your platform enough).
Yes, we were also surprised by the difference. We'd like to try with OpenJDK 8 instead to see if it's performance was better overall, but the charm for Cassandra doesn't include that as an option yet.