Interview: Torvalds gets down to the kernel

Life seems to be getting even better for Linus Torvalds. Having just taken a leave from his "day job'' at chip designer Transmeta, Torvalds is about to begin a new one at the Open Source Development Lab (OSDL) where he will be able to focus even more on completing the upcoming 2.6 version of the Linux kernel. This version is seen by most observers as critical for Linux to succeed in the enterprise because it is being refined to work more capably on large, multiprocessor systems, especially those using nonuniform memory access, and given significant improvements in scalability and more reliable performance.

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At this week's CA World 2003 show in Las Vegas, Torvalds sat down with InfoWorld Editor at Large Ed Scannell and Staff Writer Brian Fonseca to talk about the completion this past weekend of Version 2.6's first test release; what will keep him up at night worrying about that test release; his thoughts about the impending SCO-IBM suit and possible impact on Linux development; and something of a wish list of technologies to be included in upcoming versions of the open source operating system.

InfoWorld: How difficult a development effort was Version 2.6 compared with previous efforts? Are they getting increasingly difficult as you include more complex features?

Torvalds: This was fairly comparable to Version 2.4. It is hard to tell, really. I actually put out the first test release on Sunday evening [July 13], and that is the last beta of the program. With 2.4, that testing took about six or seven months to complete. But I think 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. And what I mean is that doing a release always means synchronizing. And when you have more people to synchronize it takes longer because you get more issues that come up. But on the whole it was not that different from 2.4.

InfoWorld: When you say more people were involved, what people were involved this time who have not typically been so before?

Torvalds: In previous efforts, and I mean looking back at [Version] 2.0 or the precommercial days, most of the people involved tended to be literally engineers along with some involvement of the early Linux companies. But these days you still have all the engineers, but now you also have a number of larger companies. They interact with the kernel through their own engineers but they have their own issues that they want to make sure are sorted out and things like that. So that is really where the added people came from.

InfoWorld: In joining OSDL do you think you will have more technical resources at your disposal, thereby making the development efforts easier and the delivery of future kernels faster?

Torvalds: Well, long before I joined they had their own test projects. They had their own server farms where they developed not just their own hardware tests but literally had database loads to test Linux on their own load so could verify both performance and how they were operating. That has been all independent of me. What OSDL gives me is basically a little space where I can do Linux full time. And I don’t rely on OSDL itself. I consider that very independent of what I do. It is important, but it is not like my moving there changes much.

InfoWorld: How many test versions do you anticipate putting out before the code goes to GA (general availability)?

Torvalds: It will depend. 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. And so like every other week there was a new version. But you don't want to make them too often because you want to have people actually test the test versions and really beat on them to figure out all the problems before you make the next one. Developers obviously get daily snapshots they work on, but it depends a lot on what the feedback is. It also depends on the [Linux] companies rolling out these test versions, because one thing we have found is that it is important for companies like SuSE and Red Hat to roll them out to people who are not afraid to get involved in testing pre-releases and who are normally involved in a development process. But also it is surprising how much new stuff users find that developers never do. You put a copy in front of a normal user and they find all these bugs that you would think developers would find. The real users and developers are completely different species as far as I am concerned.

InfoWorld: What areas of the kernel are you expecting developers and users to really pound on? Any one area you have concerns 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] Virtual Machine 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 tend to be not as 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 that you can't think about them that well. They depend too much on actual hardware behavior. It is hard to analyze their behavior, so that is where you want to have a lot of users just pounding on the system. So device drivers end up being my main worry, but that is always true, it is not a new issue.

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