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| | Context switch - Wikipedia, the free encyclopedia |
 | | Context switches are usually computationally intensive and much of the design of operating systems is to optimize the use of context switches. | | | A context switch is the computing process of storing and restoring the state of a CPU (the context) such that multiple processes can share a single CPU resource. | | | Context switching can be performed primarily by software or hardware. |
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http://en.wikipedia.org/wiki/Context_switch
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| | Chapter 3 |
| | 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 self-scheduling: Each message queue operation in the real-time scheduling benchmark results in a pair of context switches in the self-scheduling benchmark. |
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http://www.ecst.csuchico.edu/~walkerg/posixperf/paper/chp3/chp3.html
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| | Timing Specification Context Switch Time |
| | For example, if a task is unable to acquire a semaphore and blocks, a context switch is required to transfer control from the blocking task to a new task. | | | An RTEMS context switch is defined as the act of taking the CPU from the currently executing task and giving it to another task. | | | From the application's perspective, the context switch is a direct result of not acquiring the semaphore. |
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http://www.engr.usask.ca/classes/EP/414/lab/rtemsdocs/i960/i96000047.html
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| | Context - Wikipedia, the free encyclopedia |
| | In computer science, context is the circumstances under which a device is being used, e.g. | | | In Artificial Intelligence, context is very much related to it's properties in communications, linguistics and philosophy. | | | Research is being performed about how these aspects can be modelled in computer systems (e.g. |
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http://en.wikipedia.org/wiki/Context
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| | Processes and Process Context |
| | 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. | | | 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. | | | 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. |
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http://www.redhat.com/mirrors/LDP/LDP/LGNET/issue23/flower/context.html
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| | [No title] |
| | 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. | | | 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. | | | A secondary result shows that pinning code used to perform context switches in SRAM under the RAMpage hierarchy substantially improves average context switching time, particularly when large pages are used. |
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http://www.cs.wits.ac.za/research/abs/TR-Wits-CS-1999-2
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| | Context-Switch: Home Page |
| | 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. | | | 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. |
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http://www.context-switch.com/aboutus.htm
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| | Operating Systems Notes |
| | In a multiprogrammed uniprocessor computing system, context switches occur frequently enough that all processes appear to be running concurrently. | | | In other words, it is relatively easier for a context switch using threads. | | | If a process has more than one thread, the Operating System can use the context switching technique to schedule the threads so they appear to execute in parallel. |
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http://www.personal.kent.edu/~rmuhamma/OpSystems/Myos/threads.htm
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| | 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. | | | switch macro retlw $+1 ; return 'return' endm context equ 0x20 movlw task1 ; note task 1 will run first movwf context movlw task2 ; task switcher call $+2 ; make a place for 'switch' to return to goto $-1 ; (i.e. |
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http://www.piclist.com/techref/microchip/multitasking.htm
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| | [No title] |
| | Process switch time describes how long it takes for the computer to switch between two concurrently executing programs. | | | Also, note that using this benchmark NT is much faster than Linux at context switching, either between processes (1.9x) or threads (3.2x). | | | Since context switching occurs much more frequently than context creation, it would seem that Linux has a problem. |
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http://cs.nmu.edu/~randy/Research/Papers/Scheduler
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| | 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. | | | First, syscalls are always inducing a context switch, while context switches are not always a consequence of a system call. |
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http://www.linuxquestions.org/questions/showthread.php?t=257171
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| | ipedia.com: Interrupt Article |
| | In computer engineering, an interrupt is a signal from a device to the kernel, which typically results in a context switch. | | | The processor and interrupt code make a context switch into a specifically written piece of software to handle the interrupt. | | | Digital computers usually provide a way to start software routines in response to asynchronous electronic events. |
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http://www.ipedia.com/interrupt.html
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| | TechOnLine - RTOS Task Switching: An Example Implementation In C |
| | The process of saving the context of a task being suspended and restoring the context of a task being resumed is called context switching. | | | 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. | | | It is done this way due to the implementation of non-preemptive context switches (where a task blocks itself)—which are not described here. |
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http://www.techonline.com/community/tech_topic/rtos/feature_article/36921
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| | LWN: Patch: AIO workqueue context switch reduction |
| | The first three optimizations got me down to 360,000 context switches per second, and they help build a little structure to allow optimization #4, which uses queue_delayed_work(HZ/10) instead of queue_work. | | | During the pipetest run, 2.6 generates ~600,000 context switches per second while 2.4 generates 30 or so. | | | That brings down the number of context switches to 2.4 levels. |
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http://lwn.net/Articles/96786
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| | NetBSD Documentation: How lazy FPU context switch works |
| | The hardware supported context switch capability is costly, seldom used in practice, and many consider it as CISCy or a waste of silicon. | | | In this way, FPU context switch is deferred until a different process attempts to use the FPU. | | | In that case the cost of an MMU context switch can be reduced by having multiple memory regions and switching between them by updating dedicated register(s) via a special MMU instruction. |
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http://www.netbsd.org/Documentation/kernel/lazyfpu.html
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| | CSci 444/544, Fall 2005 Homework #1 |
| | One of pros of busy waiting is that it is efficient in cases where the expected wait time is less than the overhead of context switching out of and back to the waiting thread. | | | For example "child1->child2" signifies a context switch from child1 to child2. | | | In your answer use the notation "childX->childY" to signify a context switch. |
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http://www.cs.wm.edu/~dsn/courses/444/homework/hw1sol.html
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| | The Two-Headed UltraSPARC Client |
| | It then attempts to detect when a context switch has occurred, and when it does, it rolls the computation back to the most recent safe checkpoint and restarts from there. | | | In order to overcome this problem, the UltraSPARC DESCHALL client periodically checkpoints the state of the computation. | | | So far, it has been 100% reliable in a test environment. |
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http://www.cs.cmu.edu/People/dkindred/twoheads.html
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| | Embedded.com - Context Switch |
| | Every time software maintenance causes some code to be changed or added in the tasks which run before the mid-task switch, machine cycles need to be re-counted and task timings recalculated. | | | The schedulers which have been surveyed so far are called non-preemptive, because switching between tasks only takes place when one task has fully completed its execution and another task wants to start its execution (from its beginning). | | | With a preemptive scheduler, switching between tasks can take place at any point within the execution of a task (even when the task isn't yet done executing its code). |
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http://www.embedded.com/story/OEG20010222S0038
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| | Context Switching |
| | After the task and TSS have been created and all the relevant fields are filled in correctly, you need to create a GDT entry for the TSS, and from there you can switch to the new context at will. | | | A TSS needs to be added to the GDT before anything context switching can ever occur. | | | Most of the registers can be left alone for the application's use; however, the following fields must be filled in before you start the task initially: |
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http://www.acm.uiuc.edu/sigops/roll_your_own/5.a.html
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| | HI-TECH Software Forums: Implementing context switch or thread using hi-tech PIC C |
| | The point is that it is up to the user to manually recognize which auto-like data objects need preservation across context switches and make them static. | | | This way, they will never be reused by other functions, and their state will be preserved on a context switch. | | | on the other hand, based on my research, if we implement context switch best to have multi-threading or threading........... |
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http://www.htsoft.com/forum/all/showflat.php?Number=17944&page=
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| | Geek.com Geek News - Quicks: Context switch, Intel price cuts, Interconnects, Celeron price/power, Chipset roadmap, ... |
| | In short, Linux is actually slower than Windows 2K & XP on a context switch (under certain circumstances). | | | Sam submitted this item: Dr. Edward G. Bradford, a senior programmer at IBM, has done a few tests to show context switching speed on Windows and Linux. | | | Plus, Windows is more configurable (without recompiling the kernel, that is). |
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http://www.geek.com/news/geeknews/2002Jul/bch20020724015574.htm
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| | context switch from FOLDOC |
| | 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. | | | Many operating systems implement concurrency by maintaining separate environments or "contexts" for each process. | | | 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. |
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http://www.instantweb.com/foldoc/foldoc.cgi?context+switch
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| | Operating Systems : CPU Scheduling |
| | Comments: While the FIFO algorithm is easy to implement, it ignores the service time request and all other criteria that may influence the performance with respect to turnaround or waiting time. | | | So if one task requires some I/O operation, you want to initiate the I/O operation and go on to the next task. | | | To implement this, on a context switch, you have to |
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http://bridgeport.edu/sed/projects/cs503/Spring_2001/kode/os/scheduling.htm
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| | LWN: Patch: Prefetch kernel stacks to speed up context switch |
| | The following patch adds a hook in the schedule() function to prefetch switch stack structure as soon as 'next' task is determined. | | | This allows maximum overlap in prefetch cache lines for that structure. | | | For context switch intensive application, we found that significant amount of cache misses occurs in switch_to() function. |
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http://lwn.net/Articles/150644
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| | (WO 00/079394) METHODS AND APPARATUS FOR PROVIDING MANIFOLD ARRAY (MANARRAY) PROGRAM CONTEXT SWITCH WITH ARRAY ... |
| | In multiple PE arrays, the software controllable context switch mechanism is used to reconfigure the array to take advantage of the multiple context support the merged SP/PE (401) provides. | | | The ManArray architecture specifies a bit in the instruction format, the S/Pbit, to differentiate SP instructions from PE instructions. | | | Multiple register contexts are obtained in the ManArray processor by controlling how the array S/Pbit in the ManArray instruction format is used in conjunction with a context switch bit (CSB) for the context selection of the PE register file or the SP register file. |
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http://wipo.int/cgi-pct/guest/getbykey5?KEY=00/79394.020801&ELEMENT_SET=DECL
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| | Context Switch |
| | When OS is ready to start executing a waiting process, it loads the hardware registers from the values stored in that process' PCB. | | | The process of switching the CPU from on process to another is called a context switch. |
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http://www.scs.carleton.ca/~maheshwa/courses/300/l4/node6.html
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| | context switch - OneLook Dictionary Search |
| | context switch : Free On-line Dictionary of Computing [home, info] | | | We found 3 dictionaries with English definitions that include the word context switch: | | | Tip: Click on the first link on a line below to go directly to a page where "context switch" is defined. |
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http://www.onelook.com/cgi-bin/cgiwrap/bware/dofind.cgi?word=context+switch
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| | [Stackless] Context Switch |
| | At the moment, it only does a context switch, when either a channel is resuming a waiting takslet, or if you just schedule() to the next runnable tasklet. | | | When this is done, the stackless.run() method will grow a timeslice parameter, which controls how often to switch tasklets, automaticlly. | | | I'm just fixing some issues with the new Stacless 3.0 main feature: pickling of tasklets. |
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http://www.tismer.com/pipermail/stackless/2003-June/000749.html
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| | Context Switch |
| | Context Switch : "Piled Higher and Deeper" as one comic strip puts is. Moi working on a PhD on Static Timing Analysis for estimation of Worst-Case Execution Time. | | | Well, I got my fingers dirty and dug into html/css code and revamped Context Switch ! | | | For those of you who felt a 10-ton roller pass by over you, that's a specialisation in Real-Time systems ! |
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http://sibin.blogspot.com
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| | Virtual Memory in the IA-64 Linux Kernel |
| | Section six describes how memory coherency is maintained, that is, how Linux ensures that a process sees the correct values in the virtual memory locations it can access. | | | Section seven discusses how Linux switches execution from one address space to another, which is a necessary step during a process context switch. | | | The chapter concludes with section eight, which provides the rationale for some of the virtual memory choices that were made for the virtual memory system implemented on IA-64. |
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http://www.informit.com/articles/article.asp?p=29961&seqNum=7
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| | TMS 9900 Computer Encyclopedia Enterprise Resource Directory Complete Guide to Internet |
| | One unique feature was that all user {register}s were actually kept in memory - this included {stack pointer}s and the {program counter}. | | | A few modern designs, such as the {INMOS} {transputer}, use this same design using {cache}s or {rotating buffer}s, for the same reason of faster {context switch}es. | | | Other chips of the time, such as the {650x} series had a similar philosophy, using {index register}s, but the TMS 9900 went the farthest in this direction. |
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http://www.jaysir.com/computer-encyclopedia/t/tms-9900-computer-terms.htm
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| | [No title] |
| | i - ó m & ¨ Project 2, step-by-step ¨ Implement stack initialization Implement context switching Use test code to be sure you have done your work correctly Note: Your responsibilities are limited to the minithread.h and minithread.c files. |
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http://www.cs.cornell.edu/Courses/cs414/2001FA/cswitch.ppt
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| | Lock and Context Switch Tracing with KTR on FreeBSD |
| | Lock and Context Switch Tracing with KTR on FreeBSD | | | KTR(9) and ktrdump(8) are powerful tools for explaing system behavior in FreeBSD, as they allow tracing of a broad range of "interesting" kernel events. |
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http://www.watson.org/~robert/freebsd/netperf/ktr
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| | Movable Type plugin: MTSwitch - Arve Bersvendsen |
| | The Switch plugin for Movable Type adds Switch/Case functionality to Movable Type's templates | | | : Container tag to set up the switch/case context. | | | Make sure you have read the Comment Posting Policy and Privacy Policy before posting. |
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http://virtuelvis.com/archives/2003/03/mtswitch
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