An LCA 2012 summary

Your editor is still recovering from his journey home from Ballarat, Australia, where the 2012 linux.conf.au was held. The richness of this event can be seen in the numerous articles already published here; this article will attempt to cover a variety of talks that, for various reasons, did not turn into articles of their own.

Freedom is always a strong theme at LCA, and the 2012 version was no exception. That emphasis tends to be especially strong in the keynote talks, as should be clear from the reports on the keynotes by Bruce Perens and Jacob Appelbaum. Karen Sandler's keynote was just as concerned with freedom and just as noteworthy; it would have merited an article of its own had we not covered some of her topics from another talk back in 2010. Karen retold her chilling story of trying to get access to the source code for an implanted device designed to protect her from abrupt heart failure. Not only is that source not available to her; even the regulatory agency in the US (the FDA) charged with approving the device normally does not review the code. The presence of catastrophic bugs seems guaranteed.

In addition to simple worries about whether the device will work as needed, there is another concern: these devices are increasingly given wireless communications capabilities that allow them to be reconfigured and controlled remotely. To the extent that the security associated with that access can be verified, it seems to be notable mostly in its absence. In other words, implanted medical devices would appear to be open to a variety of denial of service attacks with extreme consequences. Given that some of them are implanted into important people (she named Dick Cheney who, as a result of his implanted device, no longer has a pulse), it only seems like a matter of time until somebody exploits one of these vulnerabilities in a high-profile way. Karen noted dryly that, given the type of people she hangs around with, it would be unwise to expose herself to such attacks; she went out of her way to get an older device with no wireless connectivity.

She pointed out that a lot of other safety-critical devices - automotive control systems were mentioned in particular - have similar problems. The solution to the problem is clear: we need more free software in safety-critical applications so that we can all review the code and convince ourselves that we can trust our lives to it. And that, she said, is why she made the move to the GNOME Foundation. GNOME's work to make free software usable and attractive in current and future systems is, she said, an important part of getting free software adopted in places where we need it to be.

Another theme at LCA has always been represented by the maker contingent: whether it's Arduino, rockets, robots, or home automation, the people who make their own toys always turn out in force at LCA. Notable among a strong set of maker-oriented talks was "Rescuing Joe" by Andrew "Tridge" Tridgell. The challenge here is to make an autonomous aircraft that can search a defined area for a lost bushwalker ("hiker," in US dialect), drop a water bottle nearby (without hitting him), then return safely back to its landing point. This challenge has been run for a few years, but nobody has yet fully achieved its goals; Tridge's team hopes to be the first to succeed.

Getting there requires the design of a complex system involving autonomous avionics, an independent failsafe mechanism that will crash the plane if it leaves the search area, computer vision systems to locate the hiker, mechanical systems to reliably drop the water bottle in the desired location, and high-bandwidth digital communications back to the launch base. The test systems currently run with a combination of Pandaboard and Arduino-based systems, but the limitations of the Arduino are becoming clear, so the avionics are likely to move to another Linux-based Pandaboard in the near future.

This project requires the writing of a lot of software, most of which is finding its way back upstream. The hardware requirements are also significant; Tridge noted that the team received a sophisticated phased-array antenna as a donation with a note reading "thanks for rsync." All told, "challenge" appears to not even begin to describe the difficulty of what this team has taken on. The whole talk, done in Tridge's classic informative and entertaining style, is well worth watching.

Rusty Russell and Matt Evans recently took a look at V6 Unix, as built for the PDP-11, and noted something obvious but interesting: it was a whole lot smaller than the systems we are running now. The cat binary on that system was all of 152 bytes - in an era when everything was statically linked - while cat on Ubuntu 11.10 weighs in at 47,696 bytes - and that is with dynamic linkage. We have seen similar growth in grep (2,190 bytes to 151,056) and ls (4,920 bytes to 105,776). So they asked: where is all this growth coming from, and what did we get for it?

What followed was an interesting look into how Unix-like systems have changed over the years; watching the video is well recommended. Their first observation was that contemporary binaries could be reduced in size by about 30% by using the GCC -Os option, which causes the compiler to optimize for size. In other words, we are paying a 30% size penalty in order to gain some speed; the actual speed benefit they measured was about 9%. But there is a lot more to it than that.

A simple program consisting of a single "return 42;" line on Ubuntu will, when build statically, weigh in at about 500,000 bytes. Rusty and Matt determined that this program, which makes no direct C library calls, was pulling in about 17% of glibc anyway. Even the simplest program, anymore, must make provisions for dynamic loading, atexit() handling, proper setuid behavior, and more. So the program gets huge but, in this case, only about 2% of the pulled-in code actually gets run. In general, they found, most of the code dragged in by contemporary programs is simply wasted space. That waste can be reduced considerably by linking against dietlibc instead of glibc, though.

How much does 64-bit capability cost? An amusing exercise in porting the V6 code to the imaginary 64-bit "PDP-44" architecture increased its size by about 50%; the size difference between 32-bit and 64-bit Ubuntu programs is rather smaller, at about 9%. Use of "modern infrastructure" (that, for example, forces malloc() to be used instead of sbrk() in all programs) bloats things by about 120%. The large growth in features (ls has 60 options) leads to a massive 440% increase in size; they also measured a 20% time overhead caused by rarely-used features in ls. It's worth noting that half of that time cost goes away when running with LANG=C, leading to the conclusion that locales and other flexibility built into contemporary systems has a large cost. In the end, though, these appear to be costs that we are willing to pay.

David Rowe gave a fascinating talk on the development of Codec2, a speech-oriented codec that is able to produce surprisingly good voice quality at data rates as low as 1,400 bits/second. To understand the math involved, one should watch the video. But even without following that aspect of things, the talk is an interesting discussion of the open development of a patent-free codec with interesting real-world applications - sufficiently interesting that it risked being classified as a munition and treated like cryptographic code.

In summary, LCA remains unique in its combination of strongly technical talks, freedom-oriented and hands-on orientation, wide variety of topics covered, and infectious Australian humor. There is a reason some of us seem to end up there every year despite the painful air-travel experiences required. Linux Australia has put together a structure that allows the conference to be handed off to a new team in a new city every year, bringing a fresh view while upholding the standards set in the previous years. With regard to upholding the standards, the LCA 2012 lived up to expectations in a seemingly effortless manner - it was a job well done indeed. They have set a high bar for the 2013 team (Canberra, January 28 to February 2) to live up to.

[ Conference videos can be found on YouTube, in Ogg format, and in WebM. Your editor would like to thank the LCA 2012 organizers for assisting with his travel to the event. ]

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