I'm not sure 20% is worth the hassle, to be honest. I did an experiment like this recently with our project compilation. Our project's pretty big, 875k LOC Java

I'm not sure 20% is worth the hassle, to be honest. I did an experiment like this recently with our project compilation. Our project's pretty big, 875k LOC Java according to SLOCCount, and takes around 15 mins to do a clean build on my workstation. I tested putting all the source, output dirs and ivy cache in a RAM disk, and was really surprised that it made less than 20% difference. I guess disk caches are really good these days.