Monday, May 18, 2009

HotOS 2009, Day One

The Twelfth Workshop on Hot Topics in Operating Systems (HotOS) is under way this week in Ascona, Switzerland, at a former nudist colony called Monte Verità. (Sadly, this aspect of the locale has not had much influence on the attendees.) HotOS is about pushing the boundaries of our field and defining new research agendas. It is typically held in a remote, beautiful location and involves an unhealthy amount of alcohol. It's also by invitation only and you usually have to get a paper accepted to attend. This year there were 84 paper submissions and 22 papers accepted.

A few highlights from Day One...

Adam Greenfield, Nokia gave a keynote talk on The Elements of Networked Urbanism. Adam painted a very broad picture of the impact of new technologies on how people in cities connect, share information, and learn about their environment. Of course, this topic is near and dear to my heart since one of my projects is building a city-scale wireless sensor network. Adam's premise is that every physical object in a city (fire hydrants, streetlights, slabs of pavement) will be networked and addressable, turning them into networked and interactive resources, not just passive objects. (Personally, I think this a bit off mark --the fact that you can give every physical object an IPv6 address doesn't mean it makes any sense to talk to it. The real issue is the protocol, not the addressing.) Adam touched on many issues -- technical, legal, social, and economic -- tying into this vision. I wish he had said more about how this will impact the poorest denizens of the world's cities, and though he mentioned the slums of Mexico City, Manila, and Nairobi, it wasn't clear how "networked urbanism" help these people very much.

Margo Seltzer got the technical sessions off to a great start with a talk on Hierarchical Filesystems are Dead. She probably made it through two slides before the ornery audience started peppering her with questions - exactly what I like to see at HotOS. Her basic argument is that files are objects with multiple attributes and forcing them into a hierarchical namespace conflates naming and storage. The proposed approach is to allow users to build their own personalized namespaces for objects (in any structure they see fit) and apply well-established techniques from the Web (like bookmarks and search).

Colin Dixon argued that we should banish network middleboxes as too expensive, complex, and difficult to manage. The talk was focused on enterprise networks (Cisco middleboxes cost several thousand dollars) and ignored the prevalance of cheap (essentially free) middleboxes in home networks. He argued that end hosts are overprovisioned so it's better to run middlebox services at the edge where they are easier to manage. (I'm not sure I buy this. It seems easier to manage a single middlebox than a bunch of possibly misconfigured end hosts.) Also, the assumption of overprovisioned hardware doesn't necessarily hold for smartphones, which are increasingly important as network clients. (Colin's response to my question on this was that you should run a proxy for smartphones. But that's a middlebox. This probably deserves a bit more thought.)

Bingsheng He from Microsoft Research Asia talked about a new apporach for optimizing dataflow queries in clouds, called wave computing. The basic idea is to co-optimize multiple concurrent queries running within a framework like DryadLINQ or MapReduce to reduce redundant computation and I/O. It wasn't clear to me how this relates to conventional multiquery optimization in database systems; Bingsheng's response was that this is a hybrid approach between conventional query optimization and streaming query optimization.

Byung-Gon Chun from Intel Research Berkeley made the case for automatic partitioning of smart phone apps between the phone and a back-end cloud. The idea is to run a "clone" of the phone image in the cloud and use it to do things like background processing, verification, and running heavyweight computations that you can't do on a phone. The proposed approach involves partitioning and migration of process state between the phone and the cloud. This strikes me as unnecessarily complex. After all, most smartphone apps are already partitioned between the phone and a back-end service -- Byung-Gon suggested that this was painful and complex for programmers, but thousands of iPhone apps and hundreds of millions of users of services like Facebook suggest otherwise.

Prabal Dutta from Berkeley made the case that mobility changes everything in sensor networks. He focused on "mobiscopes" involving mobile sensors that collect data from their environment and exchange messages opportunistically. The key idea is that if a sensor can detect and characterize its own mobility, the networking stack can use this information to do a better job at link estimation, routing, and so forth. He described some cool new hardware that has a hardware vibration detection circuit that can wake itself up when it starts moving.

Jason Waterman gave the talk for our paper on Peloton. He got a lot of good questions, mostly dealing with concerns about the overhead of our proposed global tuple space for sharing resource state across nodes. Michael Scott made the point that a "one size fits all" approach probably won't work well. That's undoubtedly true, just as it is true for the wide range of services we have built up in more conventional distributed systems (RPC, shared memory, you name it). The question is whether the overhead of our underlying mechanisms can be recouped through better coordination between nodes in managing their resources.

Over dinner, I got a chance to gab with Mothy, Dave Anderson, Garth Gibson, Prabal, George Candea, Michael Kaminsky, and Shivnath Babu on a wide range of topics, including my wacky idea about "The Next Billion Programmers". I'll blog on that one later.

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