Is it possible to import all of the Perforce history into Kiln

First look here:

Mercurial Wiki entry for converting from Perforce

Since the conversion of VC systems with different paradigms is non trivial, you might want to tweak one of the methods considered there.

If this fails totally, you can also try to convert to a intermediate VC system like, SVN, CVS, git and then to mercurial.

Once you got it in mercurial locally you can always move it up to Kiln or one of the other hosted systems.

View the original article here