摘要 :
In this paper a new task model is proposed for scheduling analysis of dependent tasks in radio stations that embed a TDMA communication protocol. TDMA is a channel access protocol that allows several stations to communicate in a s...
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In this paper a new task model is proposed for scheduling analysis of dependent tasks in radio stations that embed a TDMA communication protocol. TDMA is a channel access protocol that allows several stations to communicate in a same network, by dividing time into several time slots. Tasks handling the TDMA radio protocol are scheduled in a manner to be compliant with the TDMA configuration: task parameters such as execution times, deadlines and release times are constrained by TDMA slots. The periodic task model, commonly used in scheduling analysis, is inefficient for the accurate specification of such systems, resulting in pessimistic scheduling analysis results. To encompass this issue, this paper proposes a new task model called Dependent General Multiframe (DGMF). This model extends the existing GMF model with precedence dependency and shared resource synchronization. We show how to perform scheduling analysis with DGMF by transforming it into a transaction model and using a schedulability test we proposed. In this paper we experiment on "software radio protocols" from Thales Communications & Security, which are representative of the system we want to analyze. Experimental results show an improvement of system schedulability using the proposed analysis technique, compared to existing ones (GMF and periodic tasks). The new task model thus provides a technique to model and analyze TDMA systems with less pessimistic results.
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摘要 :
In this paper a new task model is proposed for scheduling analysis of dependent tasks in radio stations that embed a TDMA communication protocol. TDMA is a channel access protocol that allows several stations to communicate in a s...
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In this paper a new task model is proposed for scheduling analysis of dependent tasks in radio stations that embed a TDMA communication protocol. TDMA is a channel access protocol that allows several stations to communicate in a same network, by dividing time into several time slots. Tasks handling the TDMA radio protocol are scheduled in a manner to be compliant with the TDMA configuration: task parameters such as execution times, deadlines and release times are constrained by TDMA slots. The periodic task model, commonly used in scheduling analysis, is inefficient for the accurate specification of such systems, resulting in pessimistic scheduling analysis results. To encompass this issue, this paper proposes a new task model called Dependent General Multiframe (DGMF). This model extends the existing GMF model with precedence dependency and shared resource synchronization. We show how to perform scheduling analysis with DGMF by transforming it into a transaction model and using a schedulability test we proposed. In this paper we experiment on "software radio protocols" from Thales Communications & Security, which are representative of the system we want to analyze. Experimental results show an improvement of system schedulability using the proposed analysis technique, compared to existing ones (GMF and periodic tasks). The new task model thus provides a technique to model and analyze TDMA systems with less pessimistic results.
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摘要 :
Handling cache related preemption delay (CRPD) in preemptive scheduling context for real-time embedded systems still stays an open issue despite of its practical importance. Indeed, classical priority assignment algorithms are onl...
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Handling cache related preemption delay (CRPD) in preemptive scheduling context for real-time embedded systems still stays an open issue despite of its practical importance. Indeed, classical priority assignment algorithms are only optimal when preemption costs are neglected. For example, with Audsley's Optimal Priority Assignment (OPA), as the original algorithm does not take CRPD into account, it fails frequently in identifying the schedulable task sets as it happens that the algorithm qualifies a task set to be schedulable, while it is practically not because of CRPD. In this article, we propose an approach to adapt fixed priority assignment algorithms to real-time embedded systems with cache memory. For such a purpose, we propose three extensions of the original OPA algorithm that have different degrees of pessimism, different complexities, and give different results in terms of schedulable task sets coverage. Exhaustive experimentations were achieved to evaluate the proposed approaches in terms of complexity and efficiency. The result shows that our approach provides a mean to guarantee the schedulability of the real-time embedded system while taking into account CRPD.
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In this paper, a schedulability test is proposed for tree-shaped transactions with non-immediate tasks. A tree-shaped transaction is a group of precedence dependent tasks, partitioned on different processors, which may release sev...
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In this paper, a schedulability test is proposed for tree-shaped transactions with non-immediate tasks. A tree-shaped transaction is a group of precedence dependent tasks, partitioned on different processors, which may release several other tasks upon completion. When there are non-immediate tasks, tasks are not necessarily released immediately upon their predecessor's completion. The schedulability test we propose is based on an existing test that does not handle non-immediate tasks directly. Simulation results show that tighter response time upper-bounds can be accessed when effects of non-immediateness are considered. Our schedulability test is motivated by real industrial TDMA systems developed at Thales, and experimental results show it provides less pessimistic schedulability results compared to current methods used by Thales system engineers.
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摘要 :
In this paper, a schedulability test is proposed for tree-shaped transactions with non-immediate tasks. A tree-shaped transaction is a group of precedence dependent tasks, partitioned on different processors, which may release sev...
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In this paper, a schedulability test is proposed for tree-shaped transactions with non-immediate tasks. A tree-shaped transaction is a group of precedence dependent tasks, partitioned on different processors, which may release several other tasks upon completion. When there are non-immediate tasks, tasks are not necessarily released immediately upon their predecessor's completion. The schedulability test we propose is based on an existing test that does not handle non-immediate tasks directly. Simulation results show that tighter response time upper-bounds can be accessed when effects of non-immediateness are considered. Our schedulability test is motivated by real industrial TDMA systems developed at Thales, and experimental results show it provides less pessimistic schedulability results compared to current methods used by Thales system engineers.
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摘要 :
The design of hard real-time embedded systems has to comply with strong requirements with respect to time determinism and resource consumption. However, interacting tasks may induce pessimism in schedulability analysis or introduc...
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The design of hard real-time embedded systems has to comply with strong requirements with respect to time determinism and resource consumption. However, interacting tasks may induce pessimism in schedulability analysis or introduce significant overheads in memory usage. In this paper, we restrict the execution and communication models to enforce an efficient and predictable implementation. To ensure determinism, a message sent by an emitting task is delivered at its deadline. We take advantage of a wait-free specialized message queues to provide predictable and efficient implementation. The integration of such mechanisms is assisted by a model driven engineering framework1.
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摘要 :
The design of hard real-time embedded systems has to comply with strong requirements with respect to time determinism and resource consumption. However, interacting tasks may induce pessimism in schedulability analysis or introduc...
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The design of hard real-time embedded systems has to comply with strong requirements with respect to time determinism and resource consumption. However, interacting tasks may induce pessimism in schedulability analysis or introduce significant overheads in memory usage. In this paper, we restrict the execution and communication models to enforce an efficient and predictable implementation. To ensure determinism, a message sent by an emitting task is delivered at its deadline. We take advantage of a wait-free specialized message queues to provide predictable and efficient implementation. The integration of such mechanisms is assisted by a model driven engineering framework1.
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摘要 :
Model-Based Engineering is now a valuable asset to design complex real-time systems. Toolchains are assembled to cover the various stages of the process: high-level modeling, analysis and code generation. Yet tools put heterogeneo...
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Model-Based Engineering is now a valuable asset to design complex real-time systems. Toolchains are assembled to cover the various stages of the process: high-level modeling, analysis and code generation. Yet tools put heterogeneous requirements on models: specific modeling patterns must be respected so that a given analysis is performed. This creates an interoperability paradox: models must be tuned not given system requirements, but to abide to tools capabilities. In this paper, we propose a systematic process to define the definition, comparison and enforcement of tools-specific subsets. Thus, we guide the user in selecting the tools that could support its engineering process. Our contribution is illustrated in the context of the AADL Architecture Design Language.
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摘要 :
Model-Based Engineering is now a valuable asset to design complex real-time systems. Toolchains are assembled to cover the various stages of the process: high-level modeling, analysis and code generation. Yet tools put heterogeneo...
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Model-Based Engineering is now a valuable asset to design complex real-time systems. Toolchains are assembled to cover the various stages of the process: high-level modeling, analysis and code generation. Yet tools put heterogeneous requirements on models: specific modeling patterns must be respected so that a given analysis is performed. This creates an interoperability paradox: models must be tuned not given system requirements, but to abide to tools capabilities. In this paper, we propose a systematic process to define the definition, comparison and enforcement of tools-specific subsets. Thus, we guide the user in selecting the tools that could support its engineering process. Our contribution is illustrated in the context of the AADL Architecture Design Language.
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Real-Time Embedded systems must respect a wide range of non-functional properties, including safety, respect of deadlines, power or memory consumption. We note that correct hardware resource dimensioning requires taking into accou...
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Real-Time Embedded systems must respect a wide range of non-functional properties, including safety, respect of deadlines, power or memory consumption. We note that correct hardware resource dimensioning requires taking into account the impact of the whole software, both the user code and the underlying run time environment. AADL allows one to precisely capture all of them. In this article, we evaluate the AADL modeling to define memory architectures, and then verification rules to assess that the memory is correctly dimensioned. We use the REAL domain-specific language to express memory requirements (such as layout or size) and then validate them on a case-study using the VxWorks real-time kernel.
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