Torvalds gets down to the kernel

Life appears to keep getting better for Linux creator Linus Torvalds. After taking leave from his “day job” at chip designer Transmeta, Torvalds started work at the Open Source Development Lab,  where he is focused on developing the next Linux kernel, Version 2.6. At last week’s CA World show in Las Vegas, Torvalds sat down with Editor at Large Ed Scannell and Staff Writer Brian Fonseca to talk about his work.

IW: How difficult was Version 2.6 development compared with previous efforts?

Torvalds: This was fairly comparable to Version 2.4. With 2.4, testing took about six or seven months to complete, but we are actually in better shape this time. We are aiming for three months, but we will see what happens. It has gotten slightly more complicated mainly because there are now more people involved. With more people involved it takes longer because more issues get raised.

IW: How many test versions do you anticipate putting out before the code goes GA [general availability]?

Torvalds: It depends. Last time around we had 12 test versions and then one final one. We wanted to avoid the embarrassment of having to deal with last-minute changes. But we had a new version like every other week. You don’t want to make them too often because you want people to have the time to really beat on them.

IW: What areas of the kernel are you expecting developers and users to really pound on? Any area you are concerned about?

Torvalds: I am actually less concerned this time. That is one of the reasons I think 2.6 looks better than 2.4 did at this point. We had a much more stable VM system. We had a much more stable file system infrastructure. We did a lot of changes between 2.2 and 2.4, and there are lots of changes between 2.4 and 2.6 as well, but they tended to be not quite as central as some other 2.4 changes. What I end up being most nervous about are device drivers. Drivers are nasty in the sense of you can’t think about them that well. They depend too much on actual hardware behavior, so it’s hard to analyze their behavior. So, that is where you want to really have a lot of users just pounding on the system.

IW: Has the specter of the IBM-SCO suit altered the way you approach your work on the kernel?

Torvalds: From a technical angle not at all. There has been some worry about the IP [intellectual property] issues, especially early on. SCO was running around talking about IP so people ended up looking through code for anything that looked like it was SCO’s. That all kind of died down when SCO started telling us more of the details and it became clearer that the IP issue wasn’t really at the center of it.

IW: What about legal concerns for the larger Linux community?

Torvalds: You would be crazy not to have concerns about lawsuits going forward. First, it is a lawsuit and could drag on forever. But at the same time, I am personally convinced that the Linux development model itself, which is all about openness, means you have very good visibility into exactly what is happening. We don’t have a paper trail but we have an incredibly detailed electronic trail. But if something turns out to have been improper, which I think is unlikely, we already have a better system in place than any proprietary system has ever had in terms of being able to figure out what happened in a certain case.

IW: With 2.6 you focused on both new server capabilities as well as embedded devices. What about the desktop?

Torvalds: We spent a lot of time trying to make the VM system in particular very predictable. Even under heavy workloads people expect [desktop] systems to be very smooth. You do not want to have multisecond pauses because a compile took all your disk I/O or throughput away. Sounds like a simple thing but it actually ended up being a pretty hard problem.