Excellent example where CRaC [Coordinated Restore at Checkpoint, %] would be useful.

[%] https://wiki.openjdk.org/display/crac

Very interesting. Have you already investigated where is Mill's overhead spent? What can be optimized in Mill to get its time closer to just invoking the javac? Do you already have a plan?

Why is it

./mill common.compile

and

./mill clean common

but not

./mill common.clean

?