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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, like its predecessor L3 was created by German computer scientist Jochen Liedtke as a response to the poor performance of earlier microkernel-based operating systems. 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 in 1993 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 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 deployed. One variant, OKL4 from Open Kernel Labs, shipped in billions of mobile devices. ==Design paradigm== Specifying the general idea of a microkernel, Liedtke states: A concept is tolerated inside the microkernel only if moving it outside the kernel, i.e., permitting competing implementations, would prevent the implementation of the system's required functionality. In this spirit, the L4 microkernel provides few basic mechanisms: address spaces (abstracting page tables and providing memory protection), threads and scheduling (abstracting execution and providing temporal protection), and inter-process communication (for controlled communication across isolation boundaries). An operating system based on a microkernel like L4 provides services as servers in user space that monolithic kernels like Linux or older generation microkernels include internally. For example, in order to implement a secure Unix-like system, servers must provide the rights management that Mach included inside the kernel. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「L4 microkernel family」の詳細全文を読む スポンサード リンク
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