Compile kernel for various times and problem of too long time consuming

Hi all, Since I want to evaluate performance improvements by changing just one file in kernel(noop-iosched) and compiling kernel is too much time-consuming, I want to know that if I compile kernel for more than one time, does it take similar time to first time? I use following commands. If I don't use "make-kpkg clean" for next times, does it just compile the files which have been modified or it compile whole kernel package again? make-kpkg clean fakeroot make-kpkg --initrd --append-to-version=-some-string-here kernel-image kernel-headers Thanks for your help in advance, -- Amirali Shambayati Bachelor Student Computer Engineering Department Sharif University of Technology Tehran, Iran