Maybe a bit of both?
I've seen previous discussion of this theory before on LWN, along with
amazement that it hadn't slowed down yet.
There's a number of dynamics in play here of which I'll only consider a
The big one is that for many years, Linux was playing catch-up, that is,
the state-of-the-art in kernel technology was ahead of Linux so far that
it had to well more than double-time it in ordered to have any hope of
catching up in something like computer-evolution-reasonable time. That
Linux was actually doing it surprised a LOT of people, and was a major
point behind the SCO suit -- they thought /surely/ IBM or /somebody/ must
be "cheating", in ordered for Linux to be evolving as incredibly fast as
it was, toward at that point and for what they were concerned about, a
real "enterprise" kernel. Well, we all know where /that/ ended up --
there was little if any cheating going on; it was real "organic" growth,
but at a speed nobody could really account for according to previous
models, because the Linux model really /is/ different. At the same time,
however, it /did/ make us more careful, prompting the introduction of
better origins documentation and signed-off-by.
In theory, while various (now) peer kernels may still be more mature than
Linux in some areas, that space is largely gone -- we're caught up, or
close enough so the speed of change should be slowing down toward that of
the more mature kernels as we match and now forge into new territory on
our own. However, this has been predicted since the late 2.4.teen kernels
at least, but it just didn't appear to be happening. In hindsight, we
weren't as mature as we thought we were back then (a common observation in
life, I might add, as one advances in years =8^S) and we still had more
growing to do.
Since the 2.6 series, however, there /have/ been some observable changes
toward this end. While the raw volume of change hasn't really slacked off
yet, the "scariness" of the changes has been decreasing. The first big
change from that was the switch from the odd/even cycle. At first, people
thought that it'd be relatively temporary, a couple years possibly, before
something "big and disruptive" enough to all systems to really need an
alternate development tree in which to coordinate all the changes, forcing
the opening of a new official development tree. That hasn't happened.
We've managed due both to somewhat smaller less-system-wide-disruption
changes, and an accommodation of more medium-scale changes into the
ongoing stable kernel. That this arrangement has continued to work is an
indication of relative maturity both in featureset and in development team
and method. The disruptive scale has been reduced both in absolute terms
and because we are better able to cope with it in stride than ever before.
That was the first big indication the kernel was maturing, altho raw
change continued at if anything an increased pace. A second, more recent
indication that may or may not prove out over time is the lack
of "scariness" in now really a couple of kernels in a row. If the above
change could be said to mark the transition from large to medium-large
sized disruption and the ability to handle it, this new one /may/ be the
first indications of the next level, moving from medium-large to simply
medium sized change. It should be noted that while two kernels in a row
is somewhat notable, it does not a safe trend make as yet. If we see a
continuing trend of this thru the end of the year, say a couple more
kernels in a row, for four, or only three but only one scary one and then
back to "medium", then it's probably safe to say there's a marked trend.
However, that's nowhere near suggesting that everything has been invented
now, only that we're finally catching up with the state of the art
sufficiently, while at the same time enhancing our ability to cope
in-stride with what might formerly have been disruptive, that things will
normally slow down a bit as it becomes /us/ that's doing the pioneering,
breaking the new ground.
Put in the large > med-large > medium language above, that's basically
saying we might /possibly/ expect one more notch, to medium-small in the
ordinary case, before we settle into a continuing sustainable pace as the
new pioneers, where progress is much more hard-fought because nobody's
been there before. I don't believe and would actually hope it doesn't
slow down much beyond that, nor do I believe many people are suggesting
that it will. Even then, there are likely to be occasional clusters of
difficulty and increased change, back into the medium to medium-large zone
for a kernel or three, before settling back into the medium-small zone.
However, the prediction is that as we are increasingly doing our own
pioneering, the average will drop to no higher than medium, with the
outliers being only medium-large, and large-to-hugely disruptive changes
will be a thing of the past as on the forefront it tends to be much more
That's my view from this observation point. =8^)