2010 Collaboration Summit Impressions

It's a bit late, but there you have it anyway.

April 14 to 16 I attended the Linux Foundation Collaboration Summit in SFO. I was running two tracks, one on tracing and one on tools. You can see the tracks and the slides here:
http://events.linuxfoundation.org/events/collaboration-summit/slides

I was pretty busy both days, Thursday with a whole day tracing track, Friday with a half day toolchain track.

The sessions were well attended, the rooms were full, with people spilling in the hallways. Some new things were presented, like Kernelshark, by Steve Rostedt, a GUI (yes, believe it or not, a GUI) written in GTK. It is very nice, showing a timeline for traced kernel events, and you can zoom in and filter at will. It works on the latest kernels, and it requires some new things/fixes in GTK. I don't recall exactly what version of GTK though.

Dominique Toupin from Ericsson presented something about user requirements for tracing. Mostly though about who's who in the embedded world, and eclipse.
Masami and Mathieu presented an update on their work. See their slides.

The interesting thing to me was of course the new version of uprobes w/o underlying utrace presented by Jim Keniston. At the end of the session we had a discussion about the future of utrace. Roland wasn't there, butTom Tromey (also from RedHat) collected the feedback. Basically we are at a standstill now that utrace has been rejected yet again. There wasn't much advise that anybody could give, except jokingly, we decided that the only way in is to make it a part of perf events. There needs to be another refactoring, but most of all, this "killer app" that would be enabled because of utrace hasn't materialized yet. We think that having a good debugging story on Linux is enough of a killer app, for instance allowing multiple tracers, and not relying on SIGCHLD etc. I think this wasn't completely clear to the kernel community. Trying to achieve debugging via a gdb stub inside the kernel interfacing to utrace and that is controlled via the gdb remote protocol also lost its appeal (thankfully, since the gdb remote protocol is archaic). Somebody would have to be creative in how to submit utrace. It doesn't have to be called utrace (it was really a random choice, for lack of a letter that was not already used in front of the word "trace"). So basically, I think the ideas behind utrace are sound, and the necessity of a new interface is acknowledged. But I believe the integration/submission process with the kernel folks has to restart from scratch, clean slate. We'll see. There are many conferences and meetings coming up in the near future where things can be discussed further.

On the second day, Friday, we had the tools talks. It was interesting to observe the more "kernel" oriented people's behavior towards the gcc etc community. The first talk was by Mark Mitchell, about Gcc and its new plugin architecture. After that, Paolo talked about the new C++1x standard, which will be finalized in 2011. Many features are already implemented in the libstdc++ library and gcc and usable today. We had a few minutes (really, the half day track was quite short) where Bradley Kuhn from the Software Freedom Law Center explained the GPLv3 exception for gcc (due to the new gcc plugin architecture and the availability of the intermediate results from the compilation, which is a new thing). I will not try to explain, but basically you cannot take the result of the preprocessing and then use that in your own proprietary compiler. After, we had a talk by Ian Taylor about the new Gold linker. One good thing in that area is that they are trying to make gold the new default linker (for instance Fedora will use gold as the distro linker). However gold is very different from binutils' old linker. It doesn't use a linker script, for instance. The kernel has been linked with gold many times as an exercise (the ground work was done by Kris Van Hees), but this needs to be constantly tested/monitored because the kernel linker script is very complex, and uses esoteric features (Wenji is now monitoring that each kernel RC can be built with gold). It was positive that people are now aware of gold and the need for it to be ported to more architectures. It seems that the porting is very easy, with little arch dependent code. Finally Tom Tromey presented about gdb and the archer project. Archer is a development branch of gdb mostly done by RedHat, where they are focusing on better c++ printing, c++ expression parsing, and plugins. The archer work is merged regularly in the gdb mainline.

In general it was a good conference. I did miss most of the first day, because that's when I flew in. But I caught a couple of talks. Nothing earth shattering, except for Google giving each person registered a free Android phone. Yey.

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