Interview With Arjan van de Ven of Intel and Lesswatts.org

Linux Journal recently caught up with Intel's Arjan van de Ven. Van de Ven leads Intel's green Lesswatts.org initiative and is the developer of PowerTOP, one of the most acclaimed power management tools on the Linux platform.

Linux Journal: Thanks for joining us, Arjan. First off, we are curious to know what are your main duties at Intel? Do you spend most of your time with Lesswatts.org and PowerTOP or in other areas?

Arjan van de Ven: I'm leading a team of engineers that does various things, including power management and performance optimization for Linux on Intel hardware.

LJ: Do you feel that Lesswatts.org is successful thus far? If so, why? If not, why not?

van de Ven: Judging by the number of visitors, I consider Lesswatts.org a great success for users. People seem to really look for and appreciate information and tips and tricks on saving power. I look forward to more external contributions as people get more familiar with the effort.

LJ: Is there a roadmap for the future of Lesswatts.org?

van de Ven: There are various smaller and bigger projects that Intel engineers are going to work on in the future that will be part of the Lesswatts.org umbrella project; I can't disclose the specifics now, some of them are tied to features on Intel's roadmaps, other things are more general improvements to Linux power management and power savings.

LJ: What resources has Intel devoted to Lesswatts.org?

van de Ven: I'm sorry but as a matter of policy Intel does not disclose staffing or resource amounts for projects.

LJ: How optimistic are you about the possibility that tools like those found on Lesswatts.org can really make a difference in real-world power consumption?

van de Ven: We're seeing it already in distributions like the latest releases of Fedora and Ubuntu; these releases use quite a bit less power than their versions, say, a year and a half ago. (The exact numbers obviously depend on exactly what kind of hardware you're measuring it on, and what the workload is). In the commercial enterprise space the customers are much more conservative and end up consuming Linux improvements after a longer period, so most of the gain for these customers is still to come.

LJ:What prompted you to create PowerTOP, the tool you've created to help find programs that are consuming extra power when a computer is idle, thus taking advantage of the tickless Linux kernel feature?

van de Ven: Thomas Gleixner and Ingo Molnar were working on the tickless idle feature, but we weren't seeing much power savings...contrary to our expectations. It turned out user space was so incredibly busy that the OS as a whole ended up having a tick in practice. At first I started fixing individual applications, but after some time I learned the hard way that the user-space people were introducing new issues faster than I could fix them. As part of this fixing I had made some crude tools for myself (based on infrastructure that Thomas and Ingo made). I decided to turn the tools into something actually usable so that many more people (especially the developers of the software) could fix the applications.

LJ: Are there certain applications or types of applications that are the worst offenders, i.e. preventing one to take full advantage of the tickless kernel?

van de Ven: At this point, media players and certain Web applications (AJAX websites and rich content) tend to be the worst offenders. Some of it is unavoidable, but even when idle these kind of apps
tend to not behave nicely.

LJ: What is your vision for PowerTOP in the future?

van de Ven: In the next few months we'll be expanding it to track disk usage. Disks take quite a bit of power when they're in active use (at this point, more than the CPU now that the apps are fixed for that). In addition, with the advent of flash based SSDs (in devices like the Eee PC) it's also a matter of having the flash live longer, so it's two birds with one stone.

LJ: What kinds of other power or environment related issues have you been focused on lately, if any?

van de Ven: Now that the CPU side is pretty well covered, I've been looking more at other parts of the system, such as the chipset, disk and memory. Part of this ends up being device-driver work, which is harder and has a somewhat smaller reach (fix Firefox and all users benefit, fix a wireless driver and only users with that specific model of hardware benefit), but it still needs to be done as well.

LJ: What are your other computing interests besides PowerTOP?

van de Ven: I do a whole lot of different things; lately I've been looking at how to deal with the Linux kernel quality issue that keeps coming up every year (and started tracking defect reports in an automated way on http://www.kerneloops.org) and on some nasty performance behavior of Linux that really annoys me. Linux as I use it on my laptop tends to "stutter" regularly, and it's really hard to find out why, so I started creating tools to figure out what is going on (http://www.latencytop.org) and then try to fix various things in the OS to make the problem go away for me.

LJ: Thank you for the information, Arjan van de Ven. It has been fascinating to learn more about your work. We wish you continued success!

van de Ven: You're welcome.