I'd like to share a blog post that describes the work that Lightbend's Scala Team has been busy with this year:
We now run compiler performance tests across every merged pull request to help us catch performance regressions. This was motivated by a big regression in the pre-release version of Scala 2.12 which went unnoticed for months, a situation we don't want to repeat.
The benchmarks helped us pinpoint which changes were responsible for the regression, and we've not only restored the baseline performance, but bettered it by 15-30%. More improvements are planned!