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Andrew Morton on kernel development

Andrew Morton on kernel development

Posted Jun 19, 2008 13:54 UTC (Thu) by Duncan (guest, #6647)
In reply to: Andrew Morton on kernel development by giraffedata
Parent article: Andrew Morton on kernel development

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^)


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