> does nothing.  So if you 'cd /usr/src; make includes' it takes a LOT
> longer than if you break it down and run 'make includes' in each

While it is (tautologically even) clear that this is the case, perhaps
there is a chance for optimization here?  What's the difference in
time between, for example, using find (given some advance prep of the
tree) to run make includes locally where it's needed (based on
grep'ing makefiles, or having a "includes-here" flag file touched each
place needed [I'm *not* advocating this as a real solution -- just a
bit of scaffolding for measuring the over head of make!])?