Alan Cox (alan@redhat.com) said:
That isn't to say the kernel is perfect and there is a ton of optimising work still going on, different scheduling algorithms and the like but most of the slowness is from user space - some from tools, some from combinations of tools and kernel (eg linker and paging patterns) and a lot of it from sheer stupid clueless design of applications and especially of GUI libraries.
Just as a data point, in my 57-second bootup timings, a full 10.5 seconds of that is before init - so there is plenty of places to improve all around.
Bill