Twitter is a massively distributed system with thousands of machines running thousands of JVMs. In any similar big system a small change in performance and CPU utilization is multiplied thousandfold and results in big savings. Electricity costs, cooling costs, and possibly reduction of server farm size. One way to improve Java performance and reduce CPU utilization is to simply generate better machine code. Simply is obviously not trivial but doable. Twitter is going down that road and experimenting with Graal to generate better code and reduce cost.
Chris Thalinger is a software engineer working on Java Virtual Machines for over 13 years. His main expertise is in compiler technology with Just-In-Time compilation in particular. Initially being involved with the CACAO and GNU Classpath projects, the focus shifted to OpenJDK as soon as Sun made the JDK open-source. Ever since Chris has worked on the HotSpot JVM at Sun, Oracle and now at Twitter.