D-Bus in the kernel [linux.conf.au 2014]

Most more modern OS designs than Unix started out with a high-level IPC from the beginning, and then built the rest of the OS on top of it. Linux/Unix began with only the most basic low-level IPC primitives in place (Pipes and stream sockets). Building on those over time various higher-level IPC systems were built, but only very few stood the test of time or became universal. On current Linux systems the best established high-level IPC layer is D-Bus. It implements a reliable message passing scheme, with access control, multicasting, filtering, introspection and supports a flexible object model.


In this talk I'd like to discuss the kdbus IPC system, a kernel implementation of the D-Bus logic and its userspace side. kdbus takes the concepts of classic D-Bus but makes them more universally useful, reducing latency and roundtrips, and increasing bandwidth, even covering streaming usecases. (For comparison, with kdbus, a full transaction takes only 2 copy operations, even supporting zero-copy for large messages). I'll discuss the lessons we learnt from Android's binder, Solaris' doors IPC system, and Mach's port scheme. We'll discuss, how we implemented a reliable (though probabilistic) multicasting scheme, and the tricks we used in userspace to make transparent zero-copy work, without compromising on security, and providing compatibility with classic D-Bus.

kdbus will soon show up in your favourite distribution as part of the systemd package, please attend if you want to know more about the ideas behind it.

http://lca2014.linux.org.au/schedule/...
slides: http://0pointer.de/public/lca.pdf