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	Context Switch definition
		A context switch (also sometimes referred to as a process switch or a task switch) is the switching of the CPU (central processing unit) from one process or thread to another.
		A context switch can also occur as a result of a hardware interrupt, which is a signal from a hardware device (such as a keyboard, mouse, modem or system clock) to the kernel that an event (e.g., a key press, mouse movement or arrival of data from a network connection) has occurred.
		In fact, although the cost of context switching has been declining when measured in terms of the absolute amount of CPU time consumed, this appears to be due mainly to increases in CPU clock speeds rather than to improvements in the efficiency of context switching itself.
	www.bellevuelinux.org /context_switch.html (928 words)

	Info and facts on 'Context switch' (Site not responding. Last check: 2007-10-21)
		The context switch is an essential feature of a multitasking (additional info and facts about multitasking) operating system ((computer science) software that controls the execution of computer programs and may provide various services).
		Context switches are usually computationally intensive and much of the design of operating system ((computer science) software that controls the execution of computer programs and may provide various services) s is to optimize the use
		This is due mainly to two reasons: that hardware context switching does not save all the registers (only general purpose registers, not floating point (additional info and facts about floating point) registers), and associated performance issues.
	www.absoluteastronomy.com /encyclopedia/c/co/context_switch.htm (673 words)

	Context switch - Wikipedia, the free encyclopedia
		A context switch means one of register context switch, task context switch, thread context switch, process context switch.
		When a transition between user mode and kernel mode is required in an operating system, a context switch is not necessary; a mode transition is not a context switch.
		This is due mainly to two reasons: that hardware context switching does not save all the registers (only general purpose registers, not floating point registers), and associated performance issues.
	en.wikipedia.org /wiki/Context_switch (737 words)

	Context - Wikipedia, the free encyclopedia
		The context of an event includes the circumstances and conditions which "surround" it; the context of a word, sentence, or longer utterance or text includes the words that "surround" it.
		In communications and linguistics, context is the meaning of a message (such as a sentence), its relationship to other parts of the message (such as a book), the environment in which the communication occurred, and any perceptions which may be associated with the communication.
		In Sitcoms, the context is the issues and trends that surround the time that the show is set in, e.g the sitcom "I love Lucy" relflects many issues and trends from its context of the 1950's.
	en.wikipedia.org /wiki/Context (518 words)

	vagueware.com—Innovation in Software (Site not responding. Last check: 2007-10-21)
		Context switching is something programmers first learn about in University purely in terms of what happens when a CPU or operating system has to stop doing what it’s doing, and do something else for a bit.
		The next thing programmers learn about context switching is that they are expected to behave just as well as a modern CPU at context switching when they are expected to juggle dozens of projects at once.
		The context switch is something that agile isn’t designed to handle, because it assumes that as a development manager you wouldn’t be so utterly irresponsible, moronic and boneheaded to attempt to try and get a developer handling several projects at once.
	vagueware.com /2006/11/20/the-context-switch (648 words)

	Timing Specification Context Switch Time (Site not responding. Last check: 2007-10-21)
		Context switch time is often touted as a performance measure of real-time executives.
		However, a context switch is performed as part of a directive's actions and should be viewed as such when designing an application.
		In this light, the context switch time is no more relevant than the performance of any other of the executive's subroutines which are not directly accessible by the application.
	www.engr.usask.ca /classes/EP/414/lab/rtemsdocs/i960/i96000047.html (256 words)

	Context Class Loader Enhancements - Eclipsepedia
		For the purpose of this design a Context Switch is defined as the point in an execution sequence when a component boundary is crossed from one component to the next.
		Typically when a container detects a context switch it will set the context class loader on the thread to a class loader associated with the component which is being entered.
		Switching the context class loader when calling out to these types of objects will not solve a large number of usecases.
	wiki.eclipse.org /index.php/Context_Class_Loader_Enhancements (2466 words)

	Chapter 3 (Site not responding. Last check: 2007-10-21)
		The number 4s is likely to be a gross overestimate, and it ignores the three initial context switches necessary to enter the generator task, switch from the generator task to a buffer task, and switch from the buffer task to a factoring task.
		Context switches under self-scheduling: The self-scheduling benchmark forces a context switch to and from the scheduler task after every message queue operation found in the real-time benchmark.
		Context switches under real-time scheduling: In addition to the context switches of the non-shelving case, there are 2 context switches for each shelving incident: switches to and from the shelf task.
	www.ecst.csuchico.edu /~walkerg/posixperf/paper/chp3/chp3.html (1722 words)

	Chapter 10 Performance Evaluation of HLS
		The high maximum value for a context switch does not mean that any context switch actually took that long, but rather that some thread other than one belonging to the context switch test application ran for about 1.7 ms at some point during the test.
		The context switch time for the released kernel is slightly faster than the context switch time for the rebuilt kernel because post-compilation optimizations are applied to released Windows 2000 kernels--these are not available as part of the Windows source kit.
		This section presents data supporting the view that the true cost of a context switch can be much larger than the cost of executing the context switch code path in the kernel, because a newly-running thread may be forced to re-establish its working set in the processor cache.
	www.cs.utah.edu /~regehr/papers/diss/doc-wwwch10.html (4777 words)

	Processes and Process Context (Site not responding. Last check: 2007-10-21)
		This operational state data is known as its context and the act of removing the process's thread of execution from the processor (and replacing it with another) is known as a process switch or context switch.
		In the case of the process switch much more information must be saved in order to later restore the process context than in the second case where the process remains resident in memory while it's thread of execution is interrupted.
		When a process switch is made the scheduler saves the process's task_struct and replaces the current tasks pointer with a pointer to the new process's task_struct, restoring its memory access and register context.
	www.redhat.com /mirrors/LDP/LDP/LGNET/issue23/flower/context.html (458 words)

	[No title] (Site not responding. Last check: 2007-10-21)
		Performance Implications of Context Switches on Misses to DRAM Lance Pompe van Meerdevoort MSc Research Report December 1998 Final revisions April 1999 Advances in microprocessor technology have resulted in the situation where CPU performance is improving faster than DRAM main memory performance.
		This ensures a faster context switch on average and avoids the complications of recursion in the miss handler when switching on a miss causes a miss itself.
		The objective of this study is to investigate the feasibility of context switching as an approach to dealing with the increasing gap between CPU and DRAM performance and to evaluate the scalability of this approach as the speed gap widens.
	www.cs.wits.ac.za /research/abs/TR-Wits-CS-1999-2 (462 words)

	Operating Systems Notes
		Context Switching Threads are very inexpensive to create and destroy, and they are inexpensive to represent.
		Each switch of the CPU from one process to another is called a context switch.
		In a multiprogrammed uniprocessor computing system, context switches occur frequently enough that all processes appear to be running concurrently.
	www.personal.kent.edu /~rmuhamma/OpSystems/Myos/threads.htm (1659 words)

	Modules Index (Site not responding. Last check: 2007-10-21)
		Each Context object can hold references to any number of different facilities, each of which must be identified by a unique name (e.g.
		is thus provided for a context to release a facility from a context.
		For example, the 'splash' context might define it's own stash to ensure that any variables it defines are totally separated from any user variables in other contexts.
	www.template-toolkit.org /v3/modules/Template/Context.html (745 words)

	Convincing management context switching isn’t a good idea
		So to reach managers and convince them that context switching is a bad idea, make sure you speak their language.
		Between each week is a bit of time context switching to remember the state of the fixing.
		Context switching is insanity, because it guarantees everything will be late.
	www.ayeconference.com /Articles/ContextSwitching.html (1399 words)

	[No title]
		For these switches, only 4% of the time were there over 10 contexts ready to choose from at that moment, and only 0.1% of the time were there twenty or more.
		When all contexts have used their entire time slice, the scheduler recalculates the priority of all contexts using the recalc loop.
		Then the next context to run is the context at the head of the ready queue.
	cs.nmu.edu /~randy/Research/Papers/Scheduler (1372 words)

	[No title]
		These are the two files "switch.k" and "switch.s" defining and implementing the context switching.
		If you should consider ever porting Nachos to another hardware platform this is where you would have to study in detail and re-implement the context switch.
		* * Context switching is inherently machine dependent, since * the registers to be saved, how to set up an initial * call frame, etc, are all specific to a processor architecture.
	www.cs.nmt.edu /~cs325/contextswitch.txt (829 words)

	What are the drawbacks of syscalls and context switches? - LinuxQuestions.org
		Trying to reduce context switches, when possible, is certainly a good idea, as a context switch is consuming system resources and time which are lost by the application.
		Actually, AFAIK a context switch might occur when the process is waiting for a syscall to compete, if the kernel decides that the process has completed it's time slice, but it's not an additional context switch, but a scheduled (planned) one.
		the context switch that he is talking about is not the process context switch but the switch from the user mode to kernel mode when a system call is invoked.
	www.linuxquestions.org /questions/showthread.php?t=257171 (1318 words)

	Context-Switch: Home Page
		In multi-processing environments, a context switch is when one process is suspended from execution on the CPU, its current state is recorded and another process starts its execution.
		Obviously, in computer processing environments, the goal is to have good design of the CPU and the components of the computer system in order to reduce the context switch management overhead or to have a processing load that works more efficiently and does not require too many context switches.
		Also, in terms of system administration or performance management, the context switch is the change from an innefficient state to one where the computer system is performing well, being managed more efficiently and effectively or is more easily managed by client staff.
	www.context-switch.com /aboutus.htm (334 words)

	The Two-Headed UltraSPARC Client
		Every time a context switch occurs, the contents of the high-order 32 bits of the 64-bit registers may be destroyed.
		If we find there are certain environments where the context switches are not reliably detected, we may have to re-test keys processed by the "B" clients, but we can always rely on the other half of the results, from the "A" clients.
		Since the whole idea of preemptive multitasking is to hide context switches from applications, it's a bit tricky for an application to detect when a context switch has occurred, but that's what we must do to recover from the 64-bit data corruptions.
	www.cs.cmu.edu /People/dkindred/twoheads.html (691 words)

	Context switch - Computing Reference - eLook.org
		The amount of separation between processes, and the amount of information in a context, depends on the operating system but generally the OS should prevent processes interfering with each other, e.g.
		A context switch can be as simple as changing the value of the program counter and stack pointer or it might involve resetting the MMU to make a different set of memory pages available.
		In order to present the user with an impression of parallism, and to allow processes to respond quickly to external events, many systems will context switch tens or hundreds of times per second.
	www.elook.org /computing/context-switch.htm (127 words)

	ContextSwitching - iDIA Computing (Site not responding. Last check: 2007-10-21)
		Don Gray's critique of Johanna Rothman's article on Context Switching was the trigger to write up a few of my own thoughts.
		I've been interrupted while in deep concentration and, while I turned to answer the interruption, was unable to let go of the previous context enough to concentrate on the new context.
		These two tasks are roughly equal in priority and urgency, and it's not worth the inefficiency and irritation of a context switch in the middle of either one of them.
	idiacomputing.com /moin/ContextSwitching (1718 words)

	TechOnLine - RTOS Task Switching: An Example Implementation In C
		The RTOS kernel will switch between tasks as necessary to ensure the task with the highest priority that is able to run is the task given processing time.
		The process of saving the context of a task being suspended and restoring the context of a task being resumed is called context switching.
		If the application code saves the entire context on entering the ISR there is no need to save it again before performing a context switch so none of the microcontroller registers get saved twice.
	www.techonline.com /community/tech_topic/rtos/feature_article/36921 (3048 words)

	Context switch at opensource encyclopedia (Site not responding. Last check: 2007-10-21)
		Context switches usually involve the following steps, assuming process P1 is running on the CPU and process P2 is the next process to run on the CPU:
		The context of the CPU will contain the value of registers such as the program counter, processor control and general purpose registers.
		Retrieve the context of P2 from memory (usually on the stack of P2).
	wiki.tatet.com /Context_switch.html (242 words)

	Bug ID: 6193066 REGRESSION: High context switch rate on 5.0 under linux (Fedora Core 2)
		Under previous JVM (tested on 1.4.2_01 and 1.4.2_06), context switch rate (as reported by vmstat) is approx 600/per second.
		When SwingSet2 is idle, the context switch rate with JDK 1.5 is approx 1100/sec while with 1.4.2 it's about 100/sec.
		Please note the high context switch rate has relevance beyond the performance of the java application itself.
	bugs.sun.com /bugdatabase/view_bug.do?bug_id=6193066 (1217 words)

	PIC specific Multitasking
		Note that task switching is very different from the switch statement used in the C language.
		Task switching is changing the focus of the processor from one ``task'' (process) to a relatively independent task.
		If we only switch at certain points in the task, when the task specifically calls or returns to the multitasking kernel (i.e., when the task has reached a "good stopping point"), that's co-operative.
	www.piclist.com /techref/microchip/multitasking.htm (2535 words)

	CSci 444/544, Fall 2005 Homework #1 (Site not responding. Last check: 2007-10-21)
		The primary difference is that kernel-level context switches involve execution of OS code.
		The overhead observed on a kernel-level context switch is much higher than that of a user-level context switch.
		The three ways to switch from between user-mode and kernel-mode in a general-purpose operating system are in response to a system call, an interrupt, or a signal.
	www.cs.wm.edu /~dsn/courses/444/homework/hw1sol.html (1843 words)

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