Context Switching

Real-Time systems are becoming pervasive. In a Real-Time System the correctness of the system behavior depends not only on the logical results of the computations, but also on the physical instant at which these results are produced. A missed deadline in hard real-time systems is catastrophic and in soft real-time systems it can lead to a significant loss .This work talks about static and dynamic scheduling algorithms for real time task. The problem of real-time scheduling spans a broad spectrum of algorithms from simple uniprocessor to highly sophisticated multiprocessor scheduling algorithms which are priority driven and divided into three classes fixed priority, dynamic priority and hybrid priority. Finally conclusion shows that Instantaneous utilization factor scheduling Algorithm gives better result in uniprocessor scheduling algorithms and Modified Instantaneous utilization factor scheduling Algorithm gives better context switching, response time and CPU utilization as compared to previous scheduling algorithms.

The area of wireless multimedia sensor networks (WMSNs) is one of the emerging and fast growing fields in the scientific world. This has brought about developing low cost, low-power and multi-function multimedia sensor nodes networks of wirelessly interconnected that are able to ubiquitously retrieve multimedia content such as video and audio streams, still images, and scalar sensor data from the environment. However, the major fact that multimedia sensor nodes run out of energy quickly has been an issue and many energy efficient routing protocols have been proposed to solve this problem and preserve the life time of the network. This is the reason why routing techniques in wireless multimedia sensor network focus mainly on the accomplishment of power conservation. Most of the recent publications have shown so many protocols mainly designed to minimize energy consumption in sensor networks. This paper focuses on the review of such routing techniques used in wireless multimedia sensor network.

Multitasking and multiuser operating system's performance depends on the efficiency of scheduling algorithm. Most commonly used Round Robin scheduling algorithm may not give optimal result if the burst time of processes is very high as compared to the time quantum of Round Robin algorithm. In this case, context switching and turnaround time of processes is very high. In this paper, a two queue based Round Robin Scheduling Algorithm is proposed. In the proposed approach two queues are used. One queue is exclusively used for CPU intensive processes and other queue is used for I/O intensive processes. This reduces the waiting time and turnaround time when there are less or equal numbers of I/O intensive processes. Performance Analysis depending upon CPU intensive and I/O intensive processes shows that it provides better results.

Multitasking and multiuser operating system's performance depends on the efficiency of scheduling algorithm. Most commonly used Round Robin scheduling algorithm may not give optimal result if the burst time of processes is very high as compared to the time quantum of Round Robin algorithm. In this case, context switching and turnaround time of processes is very high. In this paper, a two queue based Round Robin Scheduling Algorithm is proposed. In the proposed approach two queues are used. One queue is exclusively used for CPU intensive processes and other queue is used for I/O intensive processes. This reduces the waiting time and turnaround time when there are less or equal numbers of I/O intensive processes. Performance Analysis depending upon CPU intensive and I/O intensive processes shows that it provides better results.

Managing and defining multiple tasks over different physical and digital workspaces are done by using various strategies.In this paper we put light on how computer based task management tools can support task management on a desktop or a smart phone and how it reacts in a fatal situation to the processes out of limit. The key concept in any of the operating system which allows the particular system to support multitasking system, etc. is Task Scheduling. It's the core which refers to the basic way; different processes are allowed to share the common CPU. Scheduler and dispatcher are the software which helps to carry out this project.

This paper studies online scheduling problem on parallel machines that process computing jobs arrivingstochastically in a batch pattern. With the objective function asminimizing total completion time of weighted jobs or minimizingtotal latency of job completion, we propose 'Minimizing Max Weighed Processing Time Algorithm ' and its effective implementation in web based verification of documents. With the assumptionthat the processing time of a batch of documents is a constant,the jobs with a higher weight are processed first where weighting factor is 'time' and we assume that the latency of any job exceed a given. The main objective of this paper is toadjust thejob's waiting time to eventually minimize the value of objectivefunction.

Partial and dynamic reconfiguration provides a relevant new dimension to design efficient parallel embedded systems. However, due to the encasing complexity of such systems, ensuring the consistency and parallelism management at runtime is still a key challenge. So architecture models and design methodology are required to allow for efficient component reuse and hardware reconfiguration management.This paper presents a distributed persistence management model and its implementation for reconfigurable multiprocessor systems on dynamically reconfigurable circuits. The proposed approach is inspired from the well-known component based models used in software applications development. Our model is based on membranes wrapping the systems components. The objective is to improve design productivity and ensure consistency by managing context switching and storage using modular distributed hardware controllers. These membranes are distributed and optimized with the aim to design self-adaptive systems by allowing dynamic changes in parallelism degree and contexts migration. Simulation and synthesis results are given to show performances and effectiveness of our methodology.

We consider the problem of optimal real-time scheduling of periodic tasks for multiprocessors. A number of recent papers have used the notion of fluid scheduling to guarantee optimality and improve performance. In this paper, we examine exactly how fluid scheduling techniques overcome inherent problems faced by greedy scheduling algorithms such as EDF. Based on these foundations, we describe a simple and clear optimal scheduling algorithm which serves as a least common ancestor to other recent algorithms. We provide a survey of the various fluid scheduling algorithms in this novel context.

In Round-Robin Scheduling, the time quantum is fixed and processes are scheduled such that no process uses CPU time more than one time quantum in one go. If time quantum is too large, the response time of the processes will not be tolerated in an interactive environment. If the time quantum is too small, unnecessary frequent context switch may occur. Consequently, overheads result in fewer throughputs. In this study, we propose a priority Round-Robin algorithm with dynamic quantum time (PDQT). The algorithm is used the old fixed quantum time to generate new one for each thread depending on its priority. The simple Round-Robin algorithm has been improved by about 20%. By controlling quantum time, we experience fewer context switches and shorter waiting and turnaround times, thereby obtaining higher throughput.

The Internet of Things (IoT) is a rapidly expanding space for researchers, students, and professionals. Development of IoT applications is hindered by the lack of available design tools, methodologies, and interoperability. The creation of a standards-based, open source hardware and software platform paired with full documentation and educational materials greatly aids in the accelerated development of IoT applications. This thesis provides a complete example of such a platform and provides a fertile ground for Science Technology Engineering and Math (STEM) educational opportunities. xi * * * / void JSON_Clear(); void JSON_addString(char8 * string); void JSON_addChar(uint8 char1); void JSON_newLine(void);

Sensor networks become increasingly a key technology for complex control applications. Their potential use in safety- and time-critical domains has raised the need for task scheduling mechanisms specially adapted to sensor node specific requirements, often materialized in predictable jitter-less execution of tasks characterized by different criticality levels. This paper offers an efficient scheduling solution, named Hybrid Hard Real-Time Scheduling (H²RTS), which combines a static, clock driven method with a dynamic, event driven scheduling technique, in order to provide high execution predictability, while keeping a high node Central Processing Unit (CPU) utilization factor. From the detailed, integrated schedulability analysis of the H²RTS, a set of sufficiency tests are introduced and demonstrated based on the processor demand and linear upper bound metrics. The performance and correct behavior of the proposed hybrid scheduling technique have been extensively evaluated and valid...

Process Scheduling is one of the fundamental concepts of operating system. Round robin process scheduling algorithm is optimal process scheduling algorithm in time sharing systems. The efficiency of the processor depends on the choice of time slice in time sharing systems. The time quantum taken in round robin algorithm is static due to which throughput of the processor decreases. In this paper, selection of time quantum is discussed and a new process scheduling algorithm for time sharing systems named as improved dynamic round robin algorithm is proposed. Proposed algorithm incorporates advantages of both "round robin" and "shortest job first" process scheduling algorithms which tends to reduce chances of starvation and increases throughput of the system. Round robin process scheduling algorithm has high process switch rates and accordingly average waiting time, average turnaround time and system throughput are adversely affected. This situation can be improved ...

How do we sense when a situation on the horizon has become relevant to our current task? When Merleau-Ponty describes the phenomenon, he speaks of one's attention being drawn by an affordance on the margin of one's current experience.' (Dreyfus, 2008, p. 359). Dreyfus adds: 'As I cope with a specific task in a specific situation, other situations that have in the past been relevant are right now present on the horizon of my experience as potentially (not merely possibly) relevant to my current situation.' (Dreyfus, 2008, p. 359, my italics). Wheeler (2008, p. 344) agrees both with Dreyfus' description of this phenomenon 3 and with Dreyfus' suggestion that the mechanical basis of this type of attunement to situational relevance should be understood in terms of continuous reciprocal causation (CRC), for instance Freeman's (2000a) neurodynamic model as described by Dreyfus (2008). 4 Although Wheeler now seems to be no longer a fan of representations regarding this central problem of online intelligence, he (2008, p. 346) is still ambivalent about something else, namely about the power of continuous reciprocal causation for dissolving the frame problem. It is in part this ambivalence that motivates this paper of mine. Wheeler writes that he still has a real disagreement with Dreyfus, because Dreyfus thinks that 'it's CRC that provides a causal dissolution of the intra-context frame problem and not 'just' the inter-context version [of the frame problem]' (Wheeler, 2008, p. 345). Wheeler, however, holds on to his recently introduced distinction 5 between 'intra-contex' and 'inter-contex' sensitivity to relevance and writes: 'If I am ambivalent about anything here, it's about whether CRC or situated special-purpose adaptive coupling is ontologically more basic. […T]his is where the real disagreement between Dreyfus and me lies […]' (Wheeler, 2008, p. 346). Notwithstanding this ambivalence, Wheeler (2008, p. 346) accepts implicitly that in the case of what he calls 'inter-context' sensitivity to relevance CRC is 'ontologically more basic', that is to say, more basic for dissolving the frame problem (Wheeler, 2008, p. 346), than 'situated special-purpose adaptive coupling' (henceforth SPAC) because it is its mechanistic basis: 'CRC is the causal-structural basis of fluid and flexible context-switching.' (Wheeler, 2008, p. 346). The first aim of this paper is to show that there is no basis for Wheeler's ambivalence. Given 1) the fact he accepts that CRC is more basic for dissolving the frame problem than SPAC when the full situational context is taken into account by the individual (that is to say in the case of 'inter-context' sensitivity to relevance), and 2) my

Priority Preemptive scheduling algorithm is a popular among various other algorithms for scheduling CPU, however it leads to the problem of starvation which happens when processes with lower priority are not given any chance of CPU utilization due to continuous CPU usage by processes with higher priorities. To eradicate this problem here, we have proposed a new algorithm for scheduling CPU which we call it as M odified Priority Preemptive Scheduling Algorithm based on a new approach where we are executing priority Preemptive scheduling in a round robin fashion taking the time quanta equal to the shortest burst time of all the available processes. On analyzing the results, it is observed that modified Preemptive algorithm not only solves the problem of starvation but also enhances the performance of regular Priority Preemptive algorithm by lowering the mean turnaround time and mean waiting time.

Scheduling is the central concept used frequently in Operating System. It helps in choosing the processes for execution. Round Robin (RR) is one of the most widely used CPU scheduling algorithm. But, its performance degrades with respect to context switching, which is an overhead and it occurs during each scheduling. Overall performance of the system depends on choice of an optimal time quantum, so that context switching can be reduced. In this paper, we have proposed a new variant of RR scheduling algorithm, known as Dynamic Quantum with Readjusted Round Robin (DQRRR) algorithm. We have experimentally shown that performance of DQRRR is better than RR by reducing number of context switching, average waiting time and average turnaround time.

Multiprocessors have evolved as powerful computing tools for executing dynamic real time tasks. The continual evolutions of the multiprocessor and real-time systems in the last few decades have encouraged the research and development of a new and efficient algorithm for dynamic scheduling of real-time task in multiprocessor systems. This paper proposes a compact study on dynamic real time task scheduling in multiprocessor environment using Genetic Algorithm (GA) which is a typically NP-complete problem. GA exploits the power of parallel computing which drives the solution towards optimal one. The GA, inspired by biological genetics and the process of natural selection, comprises fixed size chromosome and biological inspired genetic operators like mutation and crossover. This paper investigates the various scheduling algorithms and compares the simulation result in terms of fitness value and the percentage of success for scheduling real time tasks.

Commercial real-time operating systems are complex and feature-laden. Size and complexity require extensive adaptation and long learning times. For the most common real-life requirements, one can write a real-time executive in one afiernoon in any language. Figures 1 and 2 contrast two views of the world of real time systems-that of the operating system salesman and that of the author. Commercial products must have every known feature: pre-emptive scheduler, native OS file access, time slicing, message passing, dynamic task creation, priorities, memory allocation, event queues and flags, semaphores, mailboxes, time and calendar functions, etc. Adaptation to your system is required to prevent the kernel from occupying all available memory. This means sysgening and mastering yards of documentation in which ordinary words are used with extraordinary precision and there are significant penalties for misunderstanding. Contempcmq products may have over 50 "system calls"-each requiring register setups and/or a communication block with manifold parameters and options.

Scheduling is the central concept used frequently in Operating System. It helps in choosing the processes for execution. Round Robin (RR) is one of the most widely used CPU scheduling algorithm. But, its performance degrades with respect to context switching, which is an overhead and it occurs during each scheduling. Overall performance of the system depends on choice of an optimal time quantum, so that context switching can be reduced. In this paper, we have proposed a new variant of RR scheduling algorithm, known as Dynamic Quantum with Readjusted Round Robin (DQRRR) algorithm. We have experimentally shown that performance of DQRRR is better than RR by reducing number of context switching, average waiting time and average turnaround time.

This paper discusses the preliminary performance study of hybrid multithreaded execution model that combines software-controlled multithreaded system with hardware support for efficient context switching and threads scheduling. The hardware support for multithreading is augmented with a software thread scheduling technique called setscheduling, and their benefit to the overall performance is discussed. Set scheduling schedules multiple threads onto the hardware scheduler to minimize the software scheduling and context switching costs. An analytical model of the proposed multithreaded model is discussed and simulation results of processor utilization based on the proposed model are presented. Through simulation, we find that the hybrid multithreaded execution model results in high processor utilization than traditional softwarecontrolled multithreading. This research was supported in part by the Electronics and Telecommunications Research institute, Taejon, Korea.

This paper proposes a new novel scheduling algorithms to schedule periodic tasks for soft real time system. This is a planning based offline scheduler where tasks are scheduled on the basis of its instantaneous utilization. Here after every quantum of execution, instantaneous utilization of each task is calculated. Task which is having highest instantaneous utilization is scheduled to the processor. Since Instantaneous utilization factor(IUF) is temporarily variant factor, the priority of each task will vary continuously. Also It is often more desirable to complete some portions of every task rather than giving up completely the processing of some tasks. The Imprecise Computation Model was introduced to allow for the tradeoff of the quality of computations in favor of meeting the deadline constraints. It is observed that scheduling performance metrics such as schedulability, CPU utilization, context switching, response time and reliability are improved by this approach as compared to scheduling algorithms such as RM, EDF, LLF, MUF scheduling algorithms.

The emerging ubiquitous computing technology that belongs to the group of automatic identification technologies and has become popular is the Radio Frequency Identification System involving electromagnetic theory for identifying human beings, animals, and most importantly useful in various fields like drug discovery, tracking and distribution of various materials, and data warehouse management. In recent times, it is found that the ubiquitous technology has been extended to numerous industrial applications involving real-time decisions. This system termed as "networks of RFID systems" helps in controlling various parameters and systems in realtime environment. Scheduling of real-time systems is important since it helps in satisfying the timing constraints where tasks in real-time systems are decided on the basis of deadline, occurrence period and slack time. Few algorithms based on these criteria are Rate Monotonic (RM), Earliest Deadline First (EDF), and Least-Laxity-First (LLF) algorithms. EDF and LLF are considered to be dynamic in nature while RM is static in nature. To judge the efficiency of the algorithms two conditions like "overloaded" and "under loaded" are taken into consideration. In this article, an effort is made to combine the features of both static as well as dynamic algorithms. in order to control the real-time industrial processes. Hence the major issue of concern in this paper is to resolve two issues, one-determine the algorithm in terms of timing performance of different sub-processes so as to properly schedule them and other, how the timing constraints determine the behavior of the system need to be specified and thereby, to ensure that the algorithms meet the constraints under both overloaded and under loaded conditions.

Real time scheduling spans a broad spectrum of algorithms for simple uniprocessors to highly sophisticated multiprocessors. As the world nears the end of Moore's Law, more emphasis is being laid on the use of multi-processors in embedded systems. This has lead to a rise in several new scheduling schemes for multi-processor environments. Naturally there arises a need for an accurate comparison of the schedulabilities of each of these schemes in order to prove their superiority over others. The twofold aim of this paper is to present a technique for the exact schedulability analysis of global multi-processor schedulers and, based on this intermediary result, prove the schedulability superiority of a novel multi-processor scheduling algorithm. The exact schedulability analysis technique presented here is symbolic model checking in NuSMV, and we have used this technique to investigate the schedulability of global Instantaneous Utilization Factor (IUF) based scheduling. Our analysis shows a substantial improvement in the acceptance of task sets with heavier utilizations.

This paper proposes static and dynamic mechanisms by which MUF scheduling algorithm can be made more effective in overloaded soft real time systems (such as multimedia) using the concept of Random Dropping (RD) and negative laxity check. With introduction of RD, both ...

Partial and dynamic reconfiguration provides a relevant new dimension to design efficient parallel embedded systems. However, due to the encasing complexity of such systems, ensuring the consistency and parallelism management at runtime is still a key challenge. So architecture models and design methodology are required to allow for efficient component reuse and hardware reconfiguration management.This paper presents a distributed persistence management model and its implementation for reconfigurable multiprocessor systems on dynamically reconfigurable circuits. The proposed approach is inspired from the well-known component based models used in software applications development. Our model is based on membranes wrapping the systems components. The objective is to improve design productivity and ensure consistency by managing context switching and storage using modular distributed hardware controllers. These membranes are distributed and optimized with the aim to design self-adaptive systems by allowing dynamic changes in parallelism degree and contexts migration. Simulation and synthesis results are given to show performances and effectiveness of our methodology.

Real-time operating system (RTOS) is gaining increasing use not only in 32-bit systems but also in 16-bit systems. RTOS is different from generic OS by several unique characteristics and the use of RTOS in embedded system development proves to be more advantageous. In this paper, 9 RTOSes targeting smaller processors have been evaluated and four of the RTOSes have been selected for performance benchmarking on the same M16/62P microcontroller platform to avoid bias. Based on the comparison, the µTKernel RTOS is chosen for porting to the H8S/2377 16-bit microcontroller to demonstrate the ease of RTOS platform migration. The same version of µTKernel RTOS running on different platforms are then compared. Lastly, an application is developed with the RTOS to demonstrate the ease of multi-task application development on such microcontroller platform.

In this paper a new approach for Priority based round robin CPU scheduling algorithm is performed which improves the CPU performance in real time operating system. It retains the advantage of existing round-robin algorithms [5, 6, 8] and improves the performance. The proposed algorithm gives better performance with given priority as well as assigned priority and in both cases, minimize average waiting time which context switch number, and Average turnaround time from existing round robin algorithms. The paper gives a Graph comparative analysis of proposed algorithm with existing round robin scheduling algorithms on various cases with different combination of CPU burst varying time quantum, average waiting time, average turnaround time and number of context switches.

We consider the scheduling problem for real time applications with variable processor utilization factor. Th ey are composed of a set kernel of periodic tasks and of a flow of aperiodic tasks, all with firm deadlines. Periodic tasks are scheduled according to a PFair policy. We propose an efficient acceptance test for aperiodic traffic, which guarantees steady and predictable periodic scheduling, a very small error rate and which has a low complexity. We then compare its performances to the performances of challenger acceptance tests.

Distributed file systems are key building blocks for cloud computing applications based on the Map Reduce programming paradigm. Load balance among storage nodes is a critical function in clouds. In a load-balanced cloud, the resources can be well utilized and provisioned, maximizing the performance of Map Reduce-based applications. In such a distributed file system, the load of a node is typically proportional to the number of file chunks the node possesses. In this paper, a fully distributed load rebalancing algorithm is presented to cope with the load imbalance problem. The proposed algorithm is compared against a centralized approach in a production system and strives to balance the loads of nodes and reduce the demanded movement cost as much as possible, while taking advantage of physical network locality and node heterogeneity.

This paper proposes a new novel scheduling algorithms to schedule periodic tasks for soft real time system. This is a planning based offline scheduler where tasks are scheduled on the basis of its instantaneous utilization. Here after every quantum of execution, instantaneous utilization of each task is calculated. Task which is having highest instantaneous utilization is scheduled to the processor. Since Instantaneous utilization factor(IUF) is temporarily variant factor, the priority of each task will vary continuously. Also It is often more desirable to complete some portions of every task rather than giving up completely the processing of some tasks. The Imprecise Computation Model was introduced to allow for the tradeoff of the quality of computations in favor of meeting the deadline constraints. It is observed that scheduling performance metrics such as schedulability, CPU utilization, context switching, response time and reliability are improved by this approach as compared to scheduling algorithms such as RM, EDF, LLF, MUF scheduling algorithms.

In this paper, a new algorithm proposed for soft real time operating system. In this proposed algorithm response time is better than existing algorithm. Also within deadline all process will complete. In this proposed algorithm if we will follow its then it will give better response time as well as good waiting time and turnaround time. Most important part of proposed algorithm is context switching is very low also range of time quantum is less. Round robin algorithm is not applicable for soft real time operating system. Our proposed algorithm is applicable for soft real time operating system with better response.

This paper studies online scheduling problem on parallel machines that process computing jobs arrivingstochastically in a batch pattern. With the objective function asminimizing total completion time of weighted jobs or minimizingtotal latency of job completion, we propose 'Minimizing Max Weighed Processing Time Algorithm ' and its effective implementation in web based verification of documents. With the assumptionthat the processing time of a batch of documents is a constant,the jobs with a higher weight are processed first where weighting factor is 'time' and we assume that the latency of any job exceed a given. The main objective of this paper is toadjust thejob's waiting time to eventually minimize the value of objectivefunction.

This paper presents context switching as an alternative to selection by dwell time. The technique trades screen space for comfort and speed. By replicating the interface on two separate regions called contexts, the user can comfortably explore the whole content of a context without the effects of the Midas touch problem. Focus within a context is set by a short dwell time and fast selection is done by switching contexts. We present experimental results for a text entry application with 7 participants that show significant speed improvement over traditional fixed dwell time gaze controlled keyboards. After 8 sessions, 6 participants were able to type about 12 words per minute (wpm), and the fastest participant was able to type above 20 wpm with error rate under 2%.

This paper presents an methodology to improve the context switch overhead in cloud computing. As migration of jobs in the cloud makes context switching overhead a challenging task which increases the communication costs of cloud and results in the low utilisation. To succeed this objective, dynamic context switching parallel algorithm is purposed in this paper. In order to enhance the utilisation and computing speeds of cloud an improved strategy is used which uses dynamic context switching parallel algorithm. Purposed methodology makes changes in the decision making process of the context switch parallel algorithm dynamically considerably reducing the context switch overheads. For execution of purposed approach, a cloud simulation environment is established which significantly reduces the waiting time of jobs during execution.

This paper describes a pragmatic but portable fallback approach for creating and dispatching between the machine contexts of multiple threads of execution on Unix systems that lack a dedicated user-space context switching facility. Such a fallback approach for implementing machine contexts is a vital part of a user-space multithreading environment, if it has to achieve maximum portability across a wide range of Unix flavors. The approach is entirely based on standard Unix system facilities and ANSI-C language features and especially does not require any assembly code or platform specific tricks at all. The most interesting issue is the technique of creating the machine context for threads, which this paper explains in detail. The described approach closely follows the algorithm as implemented by the author for the popular user-space multithreading library GNU Portable Threads (GNU Pth, [25]) which this way quickly gained the status of one of the most portable user-space multithreadi...

This paper presents scheduling techniques for small embedded system. The main contribution of the work is related to the way in which the kernel is organized to schedule and dispatch tasks. This is done based on special data structures that allow a very fast search of the next higher priority task ready to execute. This is achieved without producing a significant increment on the amount of memory required to implement the mechanism and at the same time keeping the footprint smaller than other kernels.

In present era, one of the most important resources of computer machine is CPU. With the increasing number of application, there exist a large number of processes in the computer system at the same time. Many processes in system simultaneously raise a challenging circumstance of managing the CPU in such a manner that the CPU utilization and processes execution gets optimal performance. The world is still waiting for most efficient algorithm which remains a challenging issue. In this manuscript, we have proposed a new algorithm Progressively Varying Response Ratio Priority a preemptive CPU scheduling algorithm based on the Priority Algorithm and Shortest Remaining Time First. In this scheduling algorithm, the priority is been calculated and the processes with high priority get CPU first or next. For new process, the priority of it becomes equal to inverse of burst time and for the old processes the priority calculation takes place as a ratio of waiting time and remaining burst time. The objective is to get all the processes executed with minimum average waiting time and no starvation. Experiment and comparison show that the VRRP outperforms other CPU scheduling algorithms. It gives better evaluation results in the form of scheduling criteria. We have used the deterministic model to compare the different algorithms.

Real time scheduling spans a broad spectrum of algorithms for simple uniprocessors to highly sophisticated multiprocessors. As the world nears the end of Moore's Law, more emphasis is being laid on the use of multi-processors in embedded systems. This has lead to a rise in several new scheduling schemes for multi-processor environments. Naturally there arises a need for an accurate comparison of the schedulabilities of each of these schemes in order to prove their superiority over others. The twofold aim of this paper is to present a technique for the exact schedulability analysis of global multi-processor schedulers and, based on this intermediary result, prove the schedulability superiority of a novel multi-processor scheduling algorithm. The exact schedulability analysis technique presented here is symbolic model checking in NuSMV, and we have used this technique to investigate the schedulability of global Instantaneous Utilization Factor (IUF) based scheduling. Our analysis shows a substantial improvement in the acceptance of task sets with heavier utilizations.

In this paper a new approach for Priority based round robin CPU scheduling algorithm is performed which improves the CPU performance in real time operating system. It retains the advantage of existing round-robin algorithms [5, 6, 8] and improves the performance. The proposed algorithm gives better performance with given priority as well as assigned priority and in both cases, minimize average waiting time which context switch number, and Average turnaround time from existing round robin algorithms. The paper gives a Graph comparative analysis of proposed algorithm with existing round robin scheduling algorithms on various cases with different combination of CPU burst varying time quantum, average waiting time, average turnaround time and number of context switches.

uClinux is a derivation of Linux kernel intended for MMU-less processors. It provides a single shared address space for all processes while the Linux kernel provides a separate virtual address space for each process using hardware MMU (memory management unit). In this paper, we implemented Linux and uClinux kernels on the same ARM9 platform and compared the performance. The ARM9 processor features virtually indexed caches and a TLB without address space tag. Therefore Linux should flush entire cache and TLB on each context switch which is very costly. uClinux, however, contents of caches and a TLB are valid even after context- switch because the same address space is shared among all processes. We observed an order of magnitude reduction of the context switching overheads on uClinux. As a result, IPC (Inter Process Communication) performance is also better on uClinux.

We consider hard real-time systems composed of periodic tasks and of an aperiodic flow. Each task, either periodic or aperiodic, has a firm deadline. An aperiodic task is accepted within the system only if it can be completed before its deadline, without causing temporal failures for the periodic tasks or for the previously accepted aperiodic tasks. We propose an acceptance test, linear in the number of pending accepted aperiodic tasks. This protocol can be used provided the idle slots left by the periodic tasks are fairly distributed. We then propose a model-driven approach, based on Petri nets, to produce schedules with a fair distribution of the idle slots for systems of non independent periodic tasks.

Partial and dynamic reconfiguration provides a relevant new dimension to design efficient parallel embedded systems. However, due to the encasing complexity of such systems, ensuring the consistency and parallelism management at runtime is still a key challenge. So architecture models and design methodology are required to allow for efficient component reuse and hardware reconfiguration management.This paper presents a distributed persistence management model and its implementation for reconfigurable multiprocessor systems on dynamically reconfigurable circuits. The proposed approach is inspired from the well-known component based models used in software applications development. Our model is based on membranes wrapping the systems components. The objective is to improve design productivity and ensure consistency by managing context switching and storage using modular distributed hardware controllers. These membranes are distributed and optimized with the aim to design self-adaptive systems by allowing dynamic changes in parallelism degree and contexts migration. Simulation and synthesis results are given to show performances and effectiveness of our methodology.

Partial and dynamic reconfiguration provides a relevant new dimension to design efficient parallel embedded systems. However, due to the encasing complexity of such systems, ensuring the consistency and parallelism management at runtime is still a key challenge. So architecture models and design methodology are required to allow for efficient component reuse and hardware reconfiguration management.This paper presents a distributed persistence management model and its implementation for reconfigurable multiprocessor systems on dynamically reconfigurable circuits. The proposed approach is inspired from the well-known component based models used in software applications development. Our model is based on membranes wrapping the systems components. The objective is to improve design productivity and ensure consistency by managing context switching and storage using modular distributed hardware controllers. These membranes are distributed and optimized with the aim to design self-adaptive systems by allowing dynamic changes in parallelism degree and contexts migration. Simulation and synthesis results are given to show performances and effectiveness of our methodology.

The main objective of this paper is to develop a new approach for round robin C P U scheduling a l g o r i t h m which improves the performance of CPU in real time operating system. The proposed Priority based Round-Robin CPU Scheduling algorithm is based on the integration of round-robin and priority scheduling algorithm. It retains the advantage of round robin in reducing starvation and also integrates the advantage of priority scheduling. The proposed algorithm also implements the concept of aging by assigning new priorities to the processes. Existing round robin CPU scheduling algorithm cannot be implemented in real time operating system due to their high context switch rates, large waiting time, large response time, large turnaround time and less throughput. The proposed algorithm improves all the drawbacks of round robin C P U scheduling algorithm. The paper also presents the comparative analysis of proposed algorithm with existing round robin scheduling algorithm on the basis...

Changing how the operating system handles interrupt processing and scheduling can greatly reduce the difference between worst-case and average-case message latencies, thus increasing a program's perfor ma nce. nvestigations that analyze the time an operating system takes to schedule, interrupt, and "context-switch" to another process or job have helped developers produce highly optimized and tuned operating systems that can provide more than 99% sustained processor use for 20

Changing how the operating system handles interrupt processing and scheduling can greatly reduce the difference between worst-case and average-case message latencies, thus increasing a program's perfor ma nce. nvestigations that analyze the time an operating system takes to schedule, interrupt, and "context-switch" to another process or job have helped developers produce highly optimized and tuned operating systems that can provide more than 99% sustained processor use for 20

In this paper, an alternative method for Wolfe's modified simplex method is introduced. This method is easy to solve quadratic programming problem (QPP) concern with non-linear programming problem (NLPP). In linear programming models, the characteristic assumption is the linearity of the objective function and constraints. Although this assumption holds in numerous practical situations, yet we come across many situations where the objective function and some or all of the constraints are non-linear functions. The non-linearity of the functions makes the solution of the problem much more involved as compared to LPPs and there is no single algorithm like the simplex method, which can be employed to solve efficiently all NPPs.

Real-time embedded systems are widely used in many applications such as control, monitoring and aviation. Several tasks are performed under strict time constraints. In such systems, deadline miss may lead to a fatal result so that all tasks (jobs) need to be scheduled to ensure that they meet their deadline times. Scheduling policy is one of various factors that affect their performance. It determines which task or a set of tasks should be selected first from ready queue to run. This paper presents an effective dynamic scheduling approach during run-time based on using a single value such as Worst-Case Execution Time (WCET) to schedule periodic tasks in either multiprocessor or uniprocessor environments. It selects which process or a set of processes must be selected for execution. The proposed algorithm works in any realtime system such as aviation, medical and process control for power plants or chemical plants.

Many real-time application domains can benefit from flexible and open distributed architectures, such as those defined by the CORBA specification. Although CORBA is well-suited for conventional request/response applications, it is not yet suitable for real-time ...

In present era, one of the most important resources of computer machine is CPU. With the increasing number of application, there exist a large number of processes in the computer system at the same time. Many processes in system simultaneously raise a challenging circumstance of managing the CPU in such a manner that the CPU utilization and processes execution gets optimal performance. The world is still waiting for most efficient algorithm which remains a challenging issue. In this manuscript, we have proposed a new algorithm Progressively Varying Response Ratio Priority a preemptive CPU scheduling algorithm based on the Priority Algorithm and Shortest Remaining Time First. In this scheduling algorithm, the priority is been calculated and the processes with high priority get CPU first or next. For new process, the priority of it becomes equal to inverse of burst time and for the old processes the priority calculation takes place as a ratio of waiting time and remaining burst time. The objective is to get all the processes executed with minimum average waiting time and no starvation. Experiment and comparison show that the VRRP outperforms other CPU scheduling algorithms. It gives better evaluation results in the form of scheduling criteria. We have used the deterministic model to compare the different algorithms.

Real-time embedded systems are widely used in many applications such as control, monitoring and aviation. Several tasks are performed under strict time constraints. In such systems, deadline miss may lead to a fatal result so that all tasks (jobs) need to be scheduled to ensure that they meet their deadline times. Scheduling policy is one of various factors that affect their performance. It determines which task or a set of tasks should be selected first from ready queue to run. This paper presents an effective dynamic scheduling approach during run-time based on using a single value such as Worst-Case Execution Time (WCET) to schedule periodic tasks in either multiprocessor or uniprocessor environments. It selects which process or a set of processes must be selected for execution. The proposed algorithm works in any realtime system such as aviation, medical and process control for power plants or chemical plants.