Robert Love, Preemptible Kernel Maintainer Interviewed

Tom F writes: "LinuxDevices did an interesting interview with Robert Love, the maintainer of the Linux preemptible kernel along with MontaVista. It is an exciting read and has Robert's usual wit and insight."

Comments

Re:Kernel Maintainer

[Nothinman]

Obviously, you want someone that knows the kernel really well and can maintain every part of it.

That person doesn't exist, not even Linus knows every part of the kernel inside and out.

You have to trust the maintainers of their parts of the kernel because as good as Linus, Marcelo, Alan, etc are they can't know all the gotchas, etc of all the drivers and different kernel subsystems.

Aren't you taking a good developer (who can maintain every part of the kernel) away from the newer versions of the kernel?

They don't have to do it if they don't want to or don't have the time. But with Alan's recent want to not maintain 2.4.x so he can work on other things seems to say how much time is really required for the maintenance of a kernel tree.

There are only so many developers, what happens if you run out?

I highly doubt there will ever be that many currently maintained kernel versions.

You just can't win

[wowbagger]

If you maintain different kernels, people say "OHMYGOD we are forking we will all DIE"

If you roll changes into a kernel and make it unstable, people say "OHMYGOD production kernel's not stable we will all DIE"

RTFA and lighten up. The patches are being considered for 2.5. They haven't been ruled out.

Because Linux is a Macrokernel architechture OS

[ithmus]

Remember when you had to compile your device drivers into the kernel yourself instead of using a module? The idea here is that the vital OS features are part of the kernel.

The open source movement is about modifying your software and sharing it. Anyone with the ability can modify a vital OS feature and share it. voila! Many, many kernels.

But, the problem here is that real time processing does not belong in a macrokernel architechture. Look at the commercial RTOS (Real Time Operating Systems) like QNX and you will see that a microkernel architechture -- a kernel that a provides minimal feature set is favored. This is because if you are depending on time constraints, all you want in your kernel is message passing and task syncronization.

Re:Because Linux is a Macrokernel architechture OS

[renehollan]

But, the problem here is that real time processing does not belong in a macrokernel architechture.

I'm inclined to agree, but I see no reason to exclude an attempt at "poor-man's" real-time processing in a macro kernel, by making the kernel preemptable. So long as one does not have serious hard real-time constraints (e.g. manned aircraft auto-pilot) and is concerned with snappier interactive response and media streaming this seams appropriate. This is certainly the case if it can be compiled in or out at will.

Re:Because Linux is a Macrokernel architechture OS

[Cato the Elder]

It's not that "real time processing does not belong in a macrokernel architechture" it's that "macrokernel architechture does not belong in a hard real time system"

I don't see any problem with making the linux kernel preemptible to be able to make better real time garuntees. Sure, I don't think you'll ever get hard realtime, but that doesn't mean that you won't get benefits from being able to respond to interrupts even when the system is running the kernel.

("hard realtime" -- maximum interrupt latency of xxx nanoseconds. "soft realtime" -- runs fast enough, usually)

Re:Impressive.

[John Whitley]

Don't they have to study at all?

What in the heck do you think this IS? Many of the best students treat developing their coding and CS skills more like a musician or artist practicing and performing for many hours a day. It's a creative act, and can be very involving. Moreover, that level of involvement hones problem solving and practival skills that the "just a job" students can never hope to achieve.

I always wondered about students who didn't have any passion for the field. From what I've seen in both academia and industry, that "just a job" mentality reduces one's skills to "programming fodder", and would seem to be a pretty unenjoyable career.