This paper presents a memory management solution for distributedreal-time Java. The proposed model is targeted at distributed applications that require to keep their internal state and that consume a bounded memory s...
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ISBN:
(纸本)0769523560
This paper presents a memory management solution for distributedreal-time Java. The proposed model is targeted at distributed applications that require to keep their internal state and that consume a bounded memory size in their operation. The aim is to provide an alternative to the garbage collector for distributedreal-time systems and to avoid the penalties it introduces. The approach is based on the usage of scoped memory defined in The real-time Specification for Java (RTSJ). Our solution introduces constraints in the programming model and in the current distributed Java architecture. However, these are compensated by eliminating the dependency of the garbage collector in the end-to-end invocation and by achieving se cleaning with respect to the memory consumed by remote invocations.
One of the problems with Java for real-time systems is the unpredictable behavior of garbage collection (GC). GC introduces unexpected load and causes widesirable delays for real-time applications. In this paper, we p...
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ISBN:
(纸本)0769523560
One of the problems with Java for real-time systems is the unpredictable behavior of garbage collection (GC). GC introduces unexpected load and causes widesirable delays for real-time applications. In this paper, we propose a technique that reduces and bounds the memory requirements for real-time Java programs. This technique can eliminate or reduce the need for GC and allows for a more predictable execution behavior and efficient utilization of the available memory. A theoretical model is presented and a number of benchmark tests are used to evaluate this technique in PERC, NewMonics' real-time JVM, and Sun's JVM The results show that in some cases GC can be eliminated and an application's execution time decreases and becomes more predictable.
object-oriented, concurrent, and event-based programming models provide a natural framework in which to express the behavior of distributed and embedded software systems. However contemporary programming languages sti...
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ISBN:
(纸本)0769515584
object-oriented, concurrent, and event-based programming models provide a natural framework in which to express the behavior of distributed and embedded software systems. However contemporary programming languages still base their I/O primitives on a model in which the environment is assumed to be centrally controlled and synchronous, and interactions with the environment carried out through blocking subroutine calls. The gap between this view and the natural asynchrony of the real world has made event-based programming a complex and error-prone activity, despite recent focus on event-based frameworks and middleware. In this paper we present a consistent model of event-based concurrency, centered around the notion of reactive objects. This model relieves the object-oriented paradigm from the idea of transparent blocking, and naturally enforces reactivity and state consistency. We illustrate our point by a program example that offers substantial improvements in size and simplicity over a corresponding Java-based solution.
This paper presents a new mechanism for preventing resource deadlock in a distributed system. The mechanism uses the ordered and atomic multicast (OAM) services to prevent processes that concurrently share resources f...
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ISBN:
(纸本)0818684321
This paper presents a new mechanism for preventing resource deadlock in a distributed system. The mechanism uses the ordered and atomic multicast (OAM) services to prevent processes that concurrently share resources front deadlocks. OAM provides communication services which deliver messages to their destinations with the guarantees of ordering and atomicity. We show that in a number of situations, OAM is a good alternative to the existing deadlock prevention techniques.
To ensure global serializability, traditional distributed database systems implement both concurrency control and transaction commit protocols. In a distributed database systems, a commit protocol guarantees the unifo...
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ISBN:
(纸本)0769523560
To ensure global serializability, traditional distributed database systems implement both concurrency control and transaction commit protocols. In a distributed database systems, a commit protocol guarantees the uniform commitment of distributed transaction execution. In the last decade, several extensions to the transaction model adopted in traditional database systems have been proposed in order to support the functional and performance requirements of emerging advanced applications such as CAD/CAM, large software design projects and object-oriented databases. Nested transaction models have been shown to play an important role in such applications, however, these models are not yet fully studied. In this paper our contributions in the field of real-time nested transactions are two fold: (i) we propose a hierarchical and flat protocols for real-time nested transactions, called 2PC-RT-NT, and (ii) we implement a lock mechanism, called 2LP-NT-HP, to solve the data conflicts problem between nested transactions.
In this work we propose and evaluate a framework for efficient and real-time dissemination of dynamic data in distributed simulation virtual environments in a scalable fashion. A peer-to-peer overlay is used to create...
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ISBN:
(纸本)0769523560
In this work we propose and evaluate a framework for efficient and real-time dissemination of dynamic data in distributed simulation virtual environments in a scalable fashion. A peer-to-peer overlay is used to create self-organizing groups of participants. Filters that combine application-level knowledge are utilized to control the message propagations and minimize the end-to-end delays. Our approach enables nodes to trade-off processing overhead for consistency precision. Our simulation results illustrate that our techniques meet the consistency requirements of the participants, while minimizing the data transmissions and the message delays.
Organic computing is becoming the new vision for the design of complex systems, satisfying human needs for trustworthy systems that behave life-like by adapting autonomously to dynamic changes of the environment, and ...
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ISBN:
(纸本)0769523560
Organic computing is becoming the new vision for the design of complex systems, satisfying human needs for trustworthy systems that behave life-like by adapting autonomously to dynamic changes of the environment, and have self-x properties as postulated for Autonomic computing. Organic computing is a response to the threatening view of being surrounded by interacting and self-organizing systems which may become unmanageable, showing undesired emergent behavior. Major challenges for organic system design arise from the conflicting requirements to have systems that are at the same time robust and adaptive, having sufficient degrees of freedom for showing self-x properties but being open for human intervention and operating with respect to appropriate rules and constraints to prevent the occurrence of undesired emergent behavior.
In this paper, we discuss the architecture of MK, its salient features and the evolution of MK from its multi-user, timesharing origins. MK targets a mnch broader class of applications than typical real-time executive...
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ISBN:
(纸本)0818684321
In this paper, we discuss the architecture of MK, its salient features and the evolution of MK from its multi-user, timesharing origins. MK targets a mnch broader class of applications than typical real-time executives so it must provide more sophisticated functionality than the typical real-time OS (RTOS). In addition to standard features such as pre-emptive scheduling and resource partitioning. designed as a multi-level collection of frameworks that separate mechanisms from policies at each level of abstraction and enable mission specific customization. MK also provides innovative kernel abstractions such as trans-node, migrating threads and "paths", which greatly enhance both the "composibility" of the system and its ability to support a variety of end-to-end Qualities of Services.
Structuring real-time concurrent programs in the form of groups of fixed-priority processes is an old art which is appropriate for only a small fraction of modem real-timedistributedcomputing application systems. Ho...
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ISBN:
(纸本)0769519288
Structuring real-time concurrent programs in the form of groups of fixed-priority processes is an old art which is appropriate for only a small fraction of modem real-timedistributedcomputing application systems. However, it is still practiced on the basis of an insufficient technical foundation. One of the basic issues in using the fixed-priority process structuring approach is to avoid the priority inversion phenomenon. It is argued that priority inversions are essentially due to the inappropriate approach used for structuring programs including the specification of the policy for allocating resources. Several basic program structuring techniques which are effective means of avoiding priority inversions are presented.
Component-based infrastructures provide support for the development and execution of component-based si,stems. However they have limitations in their application in real-time and reliable systems, because they do not ...
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ISBN:
(纸本)0769515584
Component-based infrastructures provide support for the development and execution of component-based si,stems. However they have limitations in their application in real-time and reliable systems, because they do not integrate facilities to support these types of problems and include limitations of predictability and dependability. These infrastructures are designed to provide support to financial and e-commerce applications;they integrate as basic services the transaction, persistence, security and events. These are useful services in real-time and telecom applications, but these applications require other types of services to provide predictability and reliability. Me introduce some practical solutions to integrate OoS (Quality of Service) services in the component infrastructures and the results that their business components can expect.
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