Frugal Mobile Objects

This paper presents a computing model for resource-limited mobile devices. The originality of the model lies in the integration of a strongly-typed event-based communication paradigm with abstractions for frugal control, assuming a small footprint runtime. With our model, an application consists of a set of distributed reactive objects, called FROBs, that communicate through typed events and dynamically adapt their behavior reacting to notifications typically based on resource availability. FROBs have a logical time-slicing execution pattern that helps monitor resource consuming tasks and determine resource profiles in terms of CPU, memory, and bandwidth. The behavior of a FROB is represented by a set of stateless first-class objects. Both state and behavioral objects are referenced through a level of indirection within the FROB. This facilitates the dynamic changes of the set of event types a FROB can accept, say based on the available resources, without requiring a significant footprint of the underlying FROB runtime. We demonstrate the usability of the FROB model through our Java-based prototype and a peer-to-peer audio streaming scenario where an audio provider dynamically adjusts its quality of service by adapting to demand. The performance results of our prototype convey the small footprint of our FROB runtime (86 kilobytes). We also augmented the KVM to enable resource profiling with however a negligible overhead (less than 0.5%) and a decrease in speed of the virtual machine of at most 7%

Flexible Task Graphs:Unified Restricted Thread Programming Model for Java

DC

Reflexes: Programming Abstractions for Highly Responsive Computing in Java

... tent state as they are, e.g., when being copied by a garbage collector. These checks are enforced statically by an extension of the standard Java compiler to guarantee correctness. We describe two implementations of Reflexes: a stand-alone prototype implementation built on top of a research Java real-time virtual machine, and an implementation based on an integration of Reflexes with two existing restricted programming models into a single unified framework, Flexotask, running on top of an industrial-strength Java real-time virtual machine. Whereas the prototype implementation of Reflexes is limited to a virtual machine with uni-processor support and exploits non-standard features of the virtual machine, the latter implementation leverages the multi-processor support of an industrial-strength virtual machine with minimal extensions. For both implementations we report separately on a number of encouraging results from empirical experiments using benchmark and real-world applications. Specifically, our experiments show that Reflexes in both cases are capable of achieving sub-millisecond response time with a high degree of predictability. Keywords: Real-time systems, Java virtual machine, Memory Management, Ownership types

Reflexes: Abstractions for Highly Responsive Systems

Commercial Java virtual machines are designed to maximize the performance of applications at the expense of predictability. High throughput garbage collection algorithms, for example, can introduce pauses of 100 milliseconds or more. We are interested in supporting applications with response times in the tens of microseconds and their integration with larger timing-oblivious applications in the same Java virtual machine. We propose Reflexes, a new abstraction for writing highly responsive systems in Java and investigate the virtual machine support needed to add Reflexes to a Java environment. Our implementation of Reflexes was evaluated on several programs including an audio-processing application. We were able to run a Reflex at 22.05KHz with less than 0.2 % missed deadlines over 10 million observations, a result that compares favorably to an implementation written in C

Estudo da compatibilidade entre clones de cupuaçuzeiro, em Belém-Pará.

Achieving submillisecond response times in a managed language environment such as Java or C# requires overcoming significant challenges. In this article, we propose Reflexes, a programming model and runtime system infrastructure that lets developers seamlessly mix highly responsive tasks and timing-oblivious Java applications. Thus enabling gradual addition of real-time features, to a non-real-time application without having to resort to recoding the real-time parts in a different language such as C or Ada. Experiments with the Reflex prototype implementation show that it is possible to run a real-time task with a period of 45 μs with an accuracy of 99.996% (only 0.001% worse than the corresponding C implementation) in the presence of garbage collection and heavy load ordinary Java threads