Toward real microkernels

Abstract

The inefficient^ inflexible first generation inspired development of the vastly improved second generation^ which may yet support a variety of operating systems.HE microkernel story is full of good ideas and blind alleys. The story began with enthusiasm about the promised dramatic increase in flexibility, safety, and modularity. But over the years, enthusiasm changed to disappointment, because the first-generation microkernels were inefficient and inflexible. • Today, we observe radically new approaches to the microkernel idea that seek to avoid the old mistakes while overcoming the old constraints on flexibility and performance. Tbe second-generation microkernels may be a basis for all types of operating systems, including timesharing, multimedia, and soft and hard real time. The Kernel VisionTraditionally, the word kernel denotes the mandatory part of the operating system common to all other software. The kernel can use all features of a processor (e.g., programming the memory management unit); software running in user mode cannot execute such safety-critical operations.Most early operating systems were implemented by means of large monolithic kernels. Loosely speaking, the complete operating system-scheduling, file system, networking, de\ice drivers, memory management. paging, and more-^was packed into a single kernel.In contrast, the microkernel approach involves minimizing the kernel and implementing servers outside the kernel. Ideally, the kernel implements only address spaces, interprocess communication (IPC), and basic scheduling. All servers-even device drivers-run in user mode and are treated exactiy like any other apphcation by the kernel. Since each server has its own address space, all these objects are protected from one another.When the microkernel idea was introduced in the Jochen Liedtk 70 l<l<Hi/Viil. W. Nil © ACM 0OO2-O782/9(i/0!)0() $3,50 s<-i.iiiiitit-r licjii/Vol. :)«.No, y

Proving Fairness and Implementation Correctness of a Microkernel Scheduler

“…This first generation of microkernels such as Mach [41] or IBM's Workplace OS [21] suffered from a poor performance. When Jochen Liedtke analyzed these systems [35], he pinned the problem down to a feature-overloaded mechanism for inter-process communication (IPC). Together with a light-weight, flexible IPC mechanism [33], he proposed the minimality of hardware abstractions [34] in the kernel and suggested that servers implement the traditional services of operating systems.…”

Taming “Trusted Platforms” by Operating System Design

“…The high-level PERSEUS architecture is illustrated in Figure 2. The PERSEUS security kernel is based on the efficient L4 microkernel [25,18] that provides (i) a hardware abstraction, (ii) elementary mechanisms, and (iii) flexible policies that are required to control and protect critical system services, device drivers and resource managers as separated user-space processes (a socalled multi-server system). This prevents that errors of one component can affect others, ensures that only authorized processes can access the hardware and guarantees that only the microkernel itself is executed in the supervisor mode of the CPU.…”

Fast Control Method of Software-Managed TLB for Reducing Zero-Copy Communication Overhead

“…Microkernel operating systems (OSes) [1], [2] architecture involves the implementation of near-minimum OS functions as a kernel; these include scheduling, memory management, and interprocess communication (IPC) functions. Other OS functions are implemented as processes (OS servers).…”