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Conference report: HotOS 2011 in Napa

This week, I served as program chair for the Thirteenth Workshop on Hot Topics in Operating Systems, or HotOS 2011, which took place at the Westin Verasa in Napa, California. HotOS is a unique workshop and one of my favorite venues -- it is the place for systems researchers to put forth their most forward-thinking ideas. Unlike most conferences, HotOS takes 5-page position papers, and it's expected that the submission really represents a position, not a mature piece of technical work condensed into the shorter format.

When it's done right, HotOS is full of great, big sky papers and lots of heated discussions that give the community a chance to think about what's next. In some years, HotOS has been more like an "SOSP preview," with 5-page versions of papers that are likely to appear in a major conference a few months after the workshop. We tried to avoid that this year, and for the most part I think we were successful -- very few papers in this year's HotOS were mature enough to have been considered for SOSP (although that remains to be seen).

I've already blogged about the highly contentious cloud computing panel at HotOS. Here's the rest of the trip report.

Timothy Roscoe holding court at HotOS.
This year I tried to tinker with the conventional conference format in which speakers give 25 minute talks with 5 minutes of questions afterwards. For HotOS, this seems excessive, especially since the papers are so short. Instead, we limited speakers to 10 minutes. There was some pushback on this, but overall I think it was extremely successful: I didn't feel that anyone was rushed, speakers did a great job of staying within the time limits, and by the time a talk started to get boring, it was over.

The other side is we wanted to have room for longer discussions and debates, which often can't happen in the 5 minutes between talks. Too often you hear "let's take that offline," which is code language for "I don't want to get into that in front of the audience." This is a cop-out. At HotOS, after every couple of paper sessions we had a 30-to-45 minute "open mic" session where anybody could ask questions or just rant and rave, which gave plenty of time for more in-depth discussions and debate. At first I was worried that we wouldn't be able to fill up the time, but remarkably there was often plenty of people lined up to take the mic, and lots of great back-and-forth.

A few highlights from this years' HotOS... all of the papers are available online, although they might be limited to attendees only for a while.

Jeff Mogul from HP kicked off the workshop with a talk about reconnecting OS and architecture research. He argued that the systems community is in a rut by demanding that new systems run on commodity hardware, and the architecture community is in a rut by essentially pushing the OS out of the way. He made some great points about the opportunity for OS designs to leverage new hardware features and for the systems community not to be afraid to do so.

To prove this point, Katelin Bailey from UW gave a great talk about how OS designs could leverage fast, cheap NVRAM. The basic idea is to get rid of the gap between memory and disk-based storage altogether, which opens up a wide range of new research directions, like processes which never "die." I find this work very exciting and look forward to following their progress.

Mike Walfish from UT Austin gave a very entertaining talk about "Repair from a Chair." The idea is to allow PC users to have their machines repaired by remote techs by pushing the full software image of their machine into the cloud, where the tech could fix it in a way that the end user can still verify exactly what changes were made to their system. The talk included a nice case study drawn from interviews with Geek Squad and Genius Bar techs -- really cool. My only beef with this idea is that the problem is largely moot when you run applications in the cloud and simply repair the service, rather than the end-user's machine.

Dave Ackley from UNM gave the wackiest, most out-there talk of the conference on "Pursue Robust Indefinite Scalability." I am still not sure exactly what it is about, but the idea seems to be to build modular computers based on a cellular automaton model that can be connected together at arbitrary scales. This is why we have workshops like HotOS -- it would be really hard to get this kind of work into more conventional systems venues. Best quote from the paper: "pledge allegiance to the light cone."

Steve Rumble from Stanford talked about "It's Time for Low Latency," arguing that the time has come to build RPC systems that can achieve 10 microsecond RTTs. Back in the mid-1990s, myself and a bunch of other people spent a lot of time working on this problem, and we called 10 usec the "Culler Constant," since that was the (seemingly unattainable) goal that David Culler set forth for messaging in the Berkeley NOW cluster project. Steve's argument was that the application pull for this -- cloud computing -- is finally here so maybe it's time to revisit this problem in light of modern architectures. I would love to see someone dust off the old work on U-Net and Active Messages and see what kind of performance we can achieve today, and whether there is a role for this kind of approach in modern cluster designs.

Geoff Challen from Univ. Buffalo and Mark Hempstead from Drexel gave the most entertaining talk of the workshop on "The Case for Power-Agile Computing." The idea of the talk was that mobile devices should incorporate multiple hardware components with different power/performance characteristics to support a wide range of applications. As you can see below, Geoff was dressed as a genie and had to say "shazam" a lot.
This might be the first open-shirted presentation ever at HotOS. Let us hope it was the last.
Moises Goldszmidt from MSR gave a really energetic talk on the need for better approaches for modeling and predicting the performance of complex systems. He proposed to use intervention at various points within the system to explore its state space and uncover dependencies. To me, this sounds a lot like the classic system identification problem from control theory, and I would love to see this kind of rigorous engineering approach applied to computer systems performance management.

The traditional Wild and Crazy Ideas session did not disappoint. Margo Seltzer argued that all of the studies assuming users keep cell phones in their pocket (or somewhere on their person) failed to account for the fact that most women keep them in a bag or elsewhere. Good point: I have lost count of how many papers assume that people carry their phones on them at all times. Sam King from UIUC talked about building an app store for household robots, in which the killer app really is a killer app. Dave Andersen from CMU made some kind of extended analogy between systems researchers and an airliner getting ready to crash into a brick wall. (It made more sense with wine.)

We gave away four amazing prizes: Google ChromeOS Laptops! Dave Ackley won the "most outrageous opinion" prize for his wild-eyed thoughts on computer architecture. Vijay Vasudevan from CMU won the best poster award for a poster entitled "Why a Vector Operating System is a Terrible Idea", directly contradicting his own paper in the workshop. Chris Rossbach from MSR and Mike Walfish from UT Austin won the two best talk awards for excellent delivery and great technical content.

Finally, I'd like to thank the program committee and all of the folks at USENIX for helping to make this a great workshop.


  1. When I was a kid, I expected a college professor would be exactly like Dave Ackley. Now that I'm a stodgy, adult academic, I'm glad there are still some people in academia like him. Plus his paper is actually pretty interesting - although definitely very different.

  2. Wild and Crazy Ideas? Maybe you systems folks should bother to look at Ubicomp 2006 to find RESEARCH on where people carry their phones :) :

  3. While I think the Ubicomp paper is quite interesting, actually it completely ignores a result that its data supports, which was the entire purpose of my presentation. My claim is that research claiming proximity is inherently gender biased. I surveyed more people, far less scientifically, but both Patel (who I think is amazing) and I find that men are far more likely to be carrying their phone on-their-person or within arm's reach than women. (His number show that on-average, the female participants had their phone within arm reach 37% of the time, while the male participants had their phone on their person 59% of the time). So Patel's wonderful study simply confirms the point I was making.

  4. Regarding "Repair from a Chair." I really think that many people will continue to use non-cloud-based apps for the foreseeable future. If for no other reason, people aren't always connected. More people are connected more often, but that's not the same thing.

  5. Have you considered running HotOS as an unconference for part of the time? This would be a little tricky to pull off in conjunction with the standard peer review, but the participant driven format is in keeping with what I understand to be the spirit of HotOS.

  6. David - I actually did think about adopting an unconference model, but chickened out, in part because (a) I've never actually BEEN to an unconference before, and (b) I think most other attendees would not have either, so it would have been hard to get people on board with the format. But in theory it's a great idea.


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