Grzegorz says in #1078:
The original numbers I got back in January were wrong because I was using hacked version of incremental compiler for benchmarks. I gathered more numbers using sbt 0.13.2 and the overhead of incremental compiler [snip] As you can see, for all projects apart from Scala itself, the overhead is below 10%.
So the case was closed as invalid. Related, Ability to disable incremental compiler for CI builds was closed as won't-fix.
Is this possible?
The here answer is, no (we might be open to pull reqs).