L4 Microkernel Family

L4 Microkernel Family

L4 is a family of second-generation microkernels, generally used to implement Unix-like operating systems, but also used in a variety of other systems.

L4 was a response to the poor performance of earlier microkernel-base operating systems. German computer scientist Jochen Liedtke felt that a system designed from the start for high performance, rather than other goals, could produce a microkernel of practical use. His original implementation in hand-coded Intel i386-specific assembly language code sparked off intense interest in the computer industry. Since its introduction, L4 has been developed for platform independence and also in improving security, isolation, and robustness.

There have been various re-implementations of the original binary L4 kernel interface (ABI) and its higher level successors, including L4Ka::Pistachio (Uni Karlsruhe), L4/MIPS (UNSW) and Fiasco (TU Dresden). For this reason, the name L4 has been generalized and no longer only refers to Liedtke's original implementation. It now applies to the whole microkernel family including the L4 kernel interface and its different versions.

L4 is widely used; Open Kernel Labs claims deployment of one billion L4 kernels.