Adapted from the book Open Sources: Voices from the Open Source Revolution first published in 1999 by O'Reilly.
I'm sure we made the right decision with Linux to do as little as possible in the kernel space. At this point the honest truth is I don't envision major updates to the kernel. A successful software project should mature at some point, and then the pace of changes slows down. There aren't a lot of major new innovations in store for the kernel. It's more a question of supporting a wider range of systems than anything else: taking advantage of Linux's portability to bring it to new systems.
There will be new interfaces, but I think those will come partly from supporting the wider range of systems. For example, when you start doing clustering, suddenly you want to tell the scheduler to schedule certain groups of processes as gang scheduling and things like that. But at the same time, I don't want everybody just focusing on clustering and super-computing, because a lot of the future may be with laptops, or cards that you plug in wherever you go, or something similar, so I'd like Linux to go in that direction too.
And then there are the embedded systems were there is no user interface at all, really. You only access the system to upgrade the kernel perhaps, but otherwise they just sit there. So that's another direction for Linux. I don't think Java or Inferno (Lucent's embedded operating system) are going to succeed for embedded devices.
They have missed the significance of Moore's Law. At first it sounds good to design an optimized system specific for a particular embedded device, but by the time you have a workable design, Moore's Law will have brought the price of more powerful hardware within range, undermining the value of designing for a specific device. Everything is getting so cheap that you might as well have the same system on your desktop as in your embedded device. It will make everyone's life easier.
Symmetric Multi-Processing (SMP) is one area that will be developed. The 2.2 Linux kernel will handle four processors pretty well, and we'll develop it up to eight or sixteen processors. The support for more than four processors is already there, but not really. If you have more than four processors now, it's like throwing money at a dead horse. So that will certainly be improved.
But, if people want sixty-four processors they'll have to use a special version of the kernel, because to put that support in the regular kernel would cause performance decreases for the normal users.
Some particular application areas will continue to drive kernel development. Web serving has always been an interesting problem, because it's the one real application that is really kernel-intensive. In a way, web serving has been dangerous for me, because I get so much feedback from the community using Linux as a web-serving platform that I could easily end up optimizing only for web serving. I have to keep in mind that web serving is an important application but not everything.
Of course Linux isn't being used to its full potential even by today's web servers. Apache itself doesn't do the right thing with threads, for example.
This kind of optimization has been slowed down by the limits in network bandwidth. At present, you saturate ten-megabit networks so easily that there's no reason to optimize more. The only way to not saturate ten-megabit networks is to have lots and lots of heavy duty CGIs. But that's not what the kernel can help with. What the kernel could potentially do is directly answer requests for static pages, and pass the more complicate requests to Apache. Once faster networking is more commonplace, this will be more intriguing. But right now we don't have the critical mass of hardware to test and develop it.
The lesson from all these possible future directions is that I want Linux to be on the cutting edge, and even a bit past the edge, because what's past the edge today is what's on your desktop tomorrow.
But the most exciting developments for Linux will happen in user space, not kernel space. The changes in the kernel will seem small compared to what's happening further out in the system. From this perspective, where the Linux kernel will be isn't as interesting a question as what features will be in Red Hat 17.5 or where Wine (the Windows emulator) is going to be in a few years.
In fifteen years, I expect somebody else to come along and say, hey, I can do everything that Linux can do but I can be lean and mean about it because my system won't have twenty years of baggage holding it back. They'll say Linux was designed for the 386 and the new CPUs are doing the really interesting things differently. Let's drop this old Linux stuff. This is essentially what I did when creating Linux. And in the future, they'll be able to look at our code, and use our interfaces, and provide binary compatibility, and if all that happens I'll be happy.
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