In this paper, a vCPU (virtual CPU) migration mechanism in order to improve real-time responsiveness in a GPOS (General Purpose Operating System) is presented in the embedded multicore virtualization platform and can ...
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ISBN:
(纸本)9781479908509
In this paper, a vCPU (virtual CPU) migration mechanism in order to improve real-time responsiveness in a GPOS (General Purpose Operating System) is presented in the embedded multicore virtualization platform and can also be applied to CPS environment. In a GPOS/RTOS (realtime Operating System) virtualization system nowadays, tasks in GPOS, however, also need some degree of real-time services from the system. Unfortunately, in a traditional virtualization platform, a virtualization layer always gives RTOS vCPU higher priority and preempts the execution of GPOS. therefore, a kernel module in the GPOS is added in our virtualization system to export and boost a GPOS vCPU contexts which needs higher priority against RTOS vCPU. At the same time, in order not to sacrifice the performance of the victim RTOS vCPU, a vCPU migration mechanism is added to our virtualization system, and migrates the RTOS vCPU to a low-loading CPU when this vCPU is preempted. Performance improvement of GPOS's real-time responsiveness is also given while a detailed analysis of the overhead of the RTOS vCPU is performed as well.
Phase change memory (PCM) has emerged as a promising candidate to replace DRAM in embeddedsystems. However, it can only sustain a limited number of write operations. To solve this issue, this paper proposes a novel a...
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ISBN:
(纸本)9781479908509
Phase change memory (PCM) has emerged as a promising candidate to replace DRAM in embeddedsystems. However, it can only sustain a limited number of write operations. To solve this issue, this paper proposes a novel and effective wear-leveling technique in software level to prolong the lifetime of PCM-based embeddedsystems. A polynomialtime algorithm, Multi-Space Wear Leveling Algorithm (MWL), is proposed to achieve effective wear-leveling. the experimental results show our technique can greatly extend the lifetime of PCM-based embeddedsystems compared withthe previous work. Compared withthe method without adopting wear-leveling, it introduces no more than 0.7% extra writes and 0.6% running overhead.
this paper presents a novel online scheduling algorithm for scheduling real-time adaptive systems in which tasks may have distinct resource requirements for each of the systems' operating modes. Apart from prior w...
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ISBN:
(纸本)9780769545028
this paper presents a novel online scheduling algorithm for scheduling real-time adaptive systems in which tasks may have distinct resource requirements for each of the systems' operating modes. Apart from prior work that considers only step-wise adaptation of tasks' resource utilization during mode transition, the proposed algorithm (named EAGLE-T) enables tasks to adapt their resource utilization progressively from one mode to another in a timely manner without causing any deadline miss. the upper bound of the delay and the drift between resource utilization achieved by EAGLE-T and the ideal scheduler during mode transition are provided. Performance evaluation shows that the progressive adaptation of EAGLE-T offers improved performance over a step-wise approach (average maximal-utilization drift and mode-transition delay are reduced by up to 68.75% and 32.16%, respectively). As the probability of a mode change or the number of tasks vary, empirical results show that the resource utilization achieved by tasks scheduled using EAGLE-T is within 56% to 90% of the desired utilization (compared to 11%-81% when the step-wise scheme is used).
We utilize a multiprocessor server-based approach to schedule a general class of soft real-timesystems with stochastic execution demands, when bounded average-case tardiness is sufficient for schedulability. A key fe...
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ISBN:
(纸本)9780769545028
We utilize a multiprocessor server-based approach to schedule a general class of soft real-timesystems with stochastic execution demands, when bounded average-case tardiness is sufficient for schedulability. A key feature of the task model considered here is that the stochastic execution-time demands can have arbitrary amounts of dependence within pre-specified time intervals of bounded length. this is an important practical step forward from requiring complete independence of execution times between successive jobs of the same task. Our main result does not require the scheduler to know the execution time of each job in advance, and requires only average-case utilization to be bounded by the number of processors. this constraint is mild compared to constraints on worst-case utilization because in multiprocessor systems, worst-case execution times may be orders of magnitude higher than average-case execution times.
We propose a real-time message scheduling algorithm which is applied to schedule periodic real-time messages in ieee 802.15.4 for LR-WPAN(Low Rate Wireless Personal Area Network). the standard allows GTSs (Guaranteed ...
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Static WCET analysis is a process dedicated to derive a safe upper bound of the worst-case execution time of a program. In many real-timesystems, however, a constant global WCET estimate is not always so useful since...
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ISBN:
(纸本)9780769537870
Static WCET analysis is a process dedicated to derive a safe upper bound of the worst-case execution time of a program. In many real-timesystems, however, a constant global WCET estimate is not always so useful since a program may behave very differently depending on its configuration or mode. A parametric WCET analysis derives the upper bound as formula rather than a constant. this paper presents a new efficient algorithm that can obtain a safe parametric estimate of the WCET of a program. this algorithm is evaluated on a large set of benchmarks and compared to a previous approach to parametric WCET calculation. the evaluation shows that the new algorithm, to the cost of some imprecision, scales much better and can handle more realistic programs than the previous approach.
Energy-aware real-time multiprocessor scheduling has been studied extensively so far. However, some of the constraints associated withthe practical DVS applications have been ignored for simplicity. these constraints...
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ISBN:
(纸本)9780769537870
Energy-aware real-time multiprocessor scheduling has been studied extensively so far. However, some of the constraints associated withthe practical DVS applications have been ignored for simplicity. these constraints include discrete speed, idle power, inefficient speed, and application-specific power characteristics etc. this work targets energy-aware scheduling of periodic real-time tasks on the DVS-equipped multiprocessor systems with practical constraints. An adaptive minimal bound first-fit (AMBFF) algorithm with consideration of these realistic constraints is proposed for both dynamic-priority and fixed-priority multiprocessor scheduling. Simulation results on three commercial processor models show that our algorithm can save significantly more energy than existing algorithms.
Virtualization has been widely adopted on servers for various purposes such as server consolidation, cloud computing, and so on. Recent years, the trend spreads on embeddedsystems, although it once seemed to be an im...
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ISBN:
(纸本)9780769545028
Virtualization has been widely adopted on servers for various purposes such as server consolidation, cloud computing, and so on. Recent years, the trend spreads on embeddedsystems, although it once seemed to be an impractical idea because of the limited capability of embedded processors. To further lower the overhead of adopting virtualization on embeddedsystems, we design an optimization technique, called inline emulation, to reduce the cost spending on paravirtualizing operating systems. Inline emulation can also be used in various virtualization environments to increase the performance of emulating privileged instructions. We implement inline emulation for ARMv5 architecture and evaluate in Android Emulator. the result shows it runs much faster, up to 7.4 times, than the common paravirtualization technique for cache-related operations and suggests that it not only lowers the development cost but also increases system responsiveness.
the ratio between the number of cores and memory subsystems (i.e. banks and controllers) in many-core platforms is constantly increasing, leading to non-negligible latencies of memory operations. thus, in order to stu...
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ISBN:
(纸本)9781479908509
the ratio between the number of cores and memory subsystems (i.e. banks and controllers) in many-core platforms is constantly increasing, leading to non-negligible latencies of memory operations. thus, in order to study the worst-case execution time of an application, it is no longer sufficient to only take into account its computational requirements, but also have to be considered latencies related to its memory operations. In this paper we study a limited migrative model applied upon many-core platforms. this approach is based on a multi-kernel paradigm [3] - a promising step towards scalable and predictable many-cores, which are essential prerequisites for the integration of such systems into the real-timeembedded domain. Under that assumption, we present two analytical methods to obtain the worst-case memory traffic delays of individual applications. through experiments we test the applicability of the proposed approaches to different scenarios, and draw practical conclusions concerning routing mechanisms and a distribution of memory operations across memory controllers.
Formal models used for representing recurrent real-time processes are typically characterized by a period parameter, representing the minimum amount of timethat may elapse between successive invocations of the proces...
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ISBN:
(纸本)9780769541556
Formal models used for representing recurrent real-time processes are typically characterized by a period parameter, representing the minimum amount of timethat may elapse between successive invocations of the process. However a recently proposed model called the non-cyclic GMF model deviates from this trend: there is no single period parameter characterizing the recurrent behavior of the task. In this paper we consider schedulability analysis of real-timesystems comprised of collections of such tasks, that are to be scheduled using earliest-deadline first (EDF) scheduling on a single preemptive processor. We provide evidence that indicates that schedulability analysis for such systems is more difficult than for systems in which each recurrent task is characterized by a single period parameter, and derive a pseudo-polynomial time schedulability analysis algorithm for bounded-utilization systems of such tasks.
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