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Topic: Microkernel

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	Microkernel - Wikipedia, the free encyclopedia
		Commonly, microkernels provide services such as address space management, thread management, and inter-process communication, but not networking or display for example.
		Advantages of the microkernel approach to system design: (a) adding new service does not require modifying the kernel, (b) it is more secure as more operations are done in user mode than in kernel mode, (c) a simpler kernel design and functionality typically results in a more reliable operating system.
		Microkernels, with their extensive use of interprocess communication, need higher performance.
	en.wikipedia.org /wiki/Microkernel (2683 words)

	Microkernel-based OS Efforts
		Microkernels move many of the OS services into "user space" that on other operating systems are kept in the kernel.
		The fundamental attribute that distinguishes monolithic vs. microkernel vs. exokernel architectures is what the architecture implements in kernel space (that which runs in supervisor mode on the cpu) vs. what the architecture implements in user space (that which runs in non-supervisor mode on the cpu).
		In microkernel architectures device-drivers, virtual memory, process/task/thread management/scheduling, and other such facilities are implemented in the kernel, and parallel facilities that specialize those facilities for the operating system's personality are implemented in user-space processes.
	www.cbbrowne.com /info/microkernel.html (1967 words)

	Interface Design: Microkernels (Site not responding. Last check: 2007-10-11)
		Microkernels initially met with great enthusiasm and in the late 80s there was much work on them in both academic and commercial settings.
		After several microkernels had been built into real OSs, and were being used for real applications, people found that their performance, when measured objectively as in [Bershad 92], was quite lackluster.
		This was largely due to the development history of the microkernels which had been derived from monolithic kernels, inheriting many of their interfaces and implementation strategies [Liedtke 95].
	www.cs.cornell.edu /home/ulfar/ukernel/ukernel.html (4320 words)

	Obsolete Microkernel Dooms Mac OS X to Lag Linux in Performance
		Microkernels are mostly discredited now, however, because they have performance problems, and the benefits originally promised are a fantasy.
		I think microkernel zealots are victims of an overgeneralization: they come to UNIX from legacy systems such as Windows 3.1 and Mac OS 6, which deludes them into the impression that memory protection everywhere is an abstract, unquestionable Good.
		Microkernels make eliminating block copies more difficult because there are more memory protection barriers to copy across and because data has to be copied in and out of the formatted messages that microkernel systems pass around.
	www.linuxjournal.com /node/6105/print (1968 words)

	Object Oriented Transaction Processing in the KeyKOS Microkernel
		In addition to the checkpoint and journaling mechanisms, the microkernel uses automatic disk mirroring to ensure that no data can be lost from a single disk failure at any time.
		The KeyKOS microkernel protects against this occurrence by allocating log pages in mirrored disk storage, and completing the write operation on one page before starting it on the other.
		The microkernel's checkpoint mechanism supports the caching in virtual memory of information normally stored in disk files, while maintaining consistency and durability.
	www.cis.upenn.edu /~KeyKOS/KeyTXF/KeyTXF.html (4920 words)

	The GNU Hurd - GNU Project - Free Software Foundation (FSF)
		A microkernel provides only a limited functionality, just enough abstraction on top of the hardware to run the rest of the operating system in user space.
		GNU Mach is not the most advanced microkernel known to the planet, nor is it the fastest or smallest, but it has a rich set of interfaces and some features which make it useful as the base of the Hurd system.
		As a microkernel, GNU Mach doesn't implement a lot of the features commonly found in an operating system, but only the bare minimum that is required to implement a full operating system on top of it.
	www.gnu.org /software/hurd/gnumach.html (558 words)

	Micro Kernel
		But in reality, the performance of MicroKernel is often poor enough and the implementation is complicated enough that still today most OperatingSystems are written using MonolithicKernel.
		XNU is not a MicroKernel, it is a kernel obtained by merging the Mach MicroKernel with parts of the BSD kernel and parts specific to Darwin, all running in kernel space.
		Microkernels like L4 are much closer to this ideal, and perform much better as a result.
	c2.com /cgi/wiki?MicroKernel (746 words)

	QNX Product Overview
		Microkernel architecture offers two core mechanisms that set it apart from other architecture choices to provide a solid foundation for reliability, performance, shortened development cycles, and increased scalability.
		As a result, capabilities that are virtually impossible to implement in other architecture models, such as a monolithic systems, come for "free" in a microkernel-based system.
		Microkernel architectures have often been dismissed, due to concerns about sacrificing performance to gain reliability — defined as the additional time required to execute multiple context switches.
	www.qnx.com /tech_highlights/microkernel (384 words)

	RoughlyDrafted: The Microkernel Myth part 1
		A rapid influx of other new functionality in the core kernel space has resulted in modern versions of Unix (and Linux, which is essentially a clean room rewrite of Unix) having 2-3 million lines of code in their kernel alone.
		Microkernel refers to an approach to system design that began as a reaction to the rapid expansion of the standard Unix kernel into a fat, monolithic chunk of code.
		Microkernel development came to be seen as a way to apply this Unix design model, common in userland functions, to the kernel itself.
	www.roughlydrafted.com /0506.mk1.html (469 words)

	Dr. Dobb's \| Microkernel Scalability: Maximizing Concurrency Offered By Chip Multiprocessors \| July 18, 2005 (Site not responding. Last check: 2007-10-11)
		A microkernel operating system is designed as a set of cooperating user space processes that interact through some form of inter-process communication.
		It is not clear that using a microkernel on a chip multiprocessor will translate directly to an improvement in performance.
		It is application dependent and it is possible that even though a the microkernel is able to run more than one thread of execution to perform a system service it has nothing to do or is blocked for some reason.
	www.ddj.com /184407797 (3121 words)

	MicroKernel - Castle (Site not responding. Last check: 2007-10-11)
		Most Inversion of Control containers implementations mix different concerns resulting in a tool which is hard to test and hard to extend.
		The decision of building a simple kernel simplified the development of the container and allowed it to be easily extended to adjust to new use cases.
		The MicroKernel will inspect and attempt to satisfy component dependencies and properties as components are added.
	www.castleproject.org /index.php/MicroKernel (317 words)

	Dr. Dobb's \| Interprocess Communication & the L4 Microkernel \| October 14, 2005
		This is a function of a microkernel—arguably the primary function—and L4 microkernels handle IPC with surprising agility.
		Unfortunately, the operating-system research and development community took a strong interest in microkernel design during the same period that the Mach kernel was unable to significantly improve performance and the result of this is that today, most developers steer clear of the microkernel because of the understanding that with it comes poor performance.
		This, along with the small size of the Pistachio microkernel's IPC critical path means and the frequency that IPC is used results in the executed instructions residing entirely in the processor's L1 instruction cache most of the time.
	www.ddj.com /dept/cpp/184402030?pgno=1 (5417 words)

	L4 microkernel family - Wikipedia, the free encyclopedia
		They are microkernels that are becoming well known in the computer industry for their excellent performance and small footprint.
		The realization of drawbacks in design and performance of the Mach microkernel led a number of developers to re-examine the entire microkernel concept in the mid-1990s.
		As a proof of concept that a high performance microkernel could also be constructed in a higher level language, the group developed L4Ka::Hazelnut, a C++ version of the kernel that ran on IA32 and ARM based machines.
	en.wikipedia.org /wiki/L4_microkernel_family (1842 words)

	microkernel definition - isp.webopedia.com - The Glossary for Internet Service Providers
		A microkernel (abbreviated 5K or uK) can be considered a compact kernel as it performs only the basic functions universal to all computers.
		Designed to be integrated into different operating systems, a microkernel works with OS-specific servers that provide higher level functions.
		A microkernel is a component-based structure which improves portability at the expense of performance.
	isp.webopedia.com /TERM/M/microkernel.html (132 words)

	Green Hills Software Unleashes the Royalty-Free velOSity Microkernel
		Shipping for over seven years as the INTEGRITY kernel, the velOSity microkernel is small, fast and royalty-free, making it ideal for resource-constrained applications such as consumer and mobile electronics, computer peripherals, office automation equipment, portable data terminals and automotive electronics.
		The velOSity microkernel requires as little as 3 KB of RAM and uses a state-of-the-art architecture that never disables interrupts in systems calls, guaranteeing the fastest possible interrupt response times across all microprocessors.
		The velOSity microkernel enables exceptionally fast application development out of the box and is tightly integrated with the MULTI Integrated Development Environment (IDE), the industry’s market-leading development tool set and the Green Hills Optimizing C and C++ compilers.
	www.ghs.com /news/20040329_velosity.html (906 words)

	KeyKOS Architecture-Major microkernel features (Site not responding. Last check: 2007-10-11)
		The KeyKOS microkernel is small, runs in privileged state, is unswapped, and runs with address translation off.
		A total computing system consists of multiple levels of abstraction, including the hardware, the operating system, the file system, the database management system, etc. The function provided at each level must be carefully selected and implemented or else higher levels may be subject to penalties in performance and/or complexity of design.
		The KeyKOS microkernel itself does not provide all of the functionality conventionally associated with an operating system; rather it provides a set of primitives which allow such (guest operating system) functions to be implemented by problem mode programs in domains.
	www.cis.upenn.edu /~KeyKOS/agorics/KeyKos/architecture/Major.Micro.html (319 words)

	The Neutrino Microkernel
		Neutrino is a microkernel implementation of the core POSIX 1003.1, 1003.1a, 1003.1b, 1003.1c, and 1003.1d features used in embedded realtime systems, along with the fundamental QNX message-passing services.
		The execution of a running thread is temporarily suspended whenever the microkernel is entered as the result of a kernel call, exception, or hardware interrupt.
		Since the microkernel's call interface is implemented via software interrupts (which work exactly like hardware interrupts), kernel call processing works essentially the same as interrupt processing.
	www.swd.de /documents/manuals/neutrino/kernel_en.html (13201 words)

	Sartoris Microkernel (Site not responding. Last check: 2007-10-11)
		A task is composed by a virtual address space, a set of inter task communication objects, and a set of permissions for accessing the input/output address space.
		The microkernel memory-sharing mechanism allows a task to share portions of its address space with other tasks in a secure way.
		We are also porting the microkernel to a x86-like architecture, simulated using single process in a Linux machine.
	sartoris.sourceforge.net (262 words)

	IoC:MicroKernel architecture - Castle (Site not responding. Last check: 2007-10-11)
		The MicroKernel is the result of several design attempts to create an easily extensible container that can grow both horizontally and vertically.
		The MicroKernel is the core for Castle Inversion of Control ambitions.
		The MicroKernel does not provide an implementation of IProxyFactory, this is left to Windsor so the MicroKernel can be used with fewer dependencies.
	www.castleproject.org /index.php/IoC:MicroKernel_architecture (2083 words)

	The Off++ microkernel
		The third version of the system (known as Off++v2) is rather different from the original design and is named Plan B.
		The 2K OS is a distributed adaptable OS using Off++ as a nucleus.
		The OS toolkit (OSKit) developed at Utah as part of the Flux project has been used to develop the both the old Off and the new Off++ microkernel.
	plan9.escet.urjc.es /who/nemo/off.html (452 words)

	Microkernel Operating Systems Software Computers
		Based on small microkernel that does process management, interprocess communication; all other services are processes out of kernel.
		Built from first principles to focus on small size, modularity, and be fully compatible with Win32 and industry standards; reads FAT-12/16/32.
		Brief, clear descriptions and critiquing of microkernel design concepts, with some links.
	www.iaswww.com /ODP/Computers/Software/Operating_Systems/Microkernel (301 words)

	Omniseek: /Computing /Software /Operating Systems /Microkernel /
		OUVERTURE (6603) The objective of OUVERTURE is to add value to a market standard, Unix System V Release 4 (SVR4), through the addition of the Chorus distributed Microkernel technology and other object-oriented technologies.
		Write an essay describing your ideal microkernel, keeping your document to be less than eight mosiac pages at a reasonable font size.
		Microkernel -based and Similar Operating Systems some very old ideas in operating systems with some newer ideas
	www.omniseek.com /srch/{23300} (555 words)

	Coyotos Microkernel Specification (via CobWeb/3.1 planetlab-01.bu.edu) (Site not responding. Last check: 2007-10-11)
		It is a microkernel in the sense that it is a minimal protected platform on which a complete operating system can be constructed.
		It is a security microkernel in the sense that it is a minimal protected platform on which higher level security policies can be constructed.
		EROS [5] was a small, robust microkernel whose central design ideas were pervasive use of capabilities [13] as the fundamental access model, an atomic, blocking capability invocation (therefore atomic and blocking IPC) model, and a persistent single-level store [6].
	www.eros-os.com.cob-web.org:8888 /docs/ukernel/spec.html (11183 words)

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