Lightweight POSIX tracing

In embedded systems, the typical host/target development scheme normally requires a tracing mechanism to be available in the target system in order to collect run‐time information of the application. This information is then used in the host system to debug, monitor, fine tune, etc., the application. Related to this, POSIX has recently incorporated the definition of standard tracing services into the complete POSIX 1003.1‐2001 standard. It is obvious that standard interfaces present several advantages for applications, specially regarding portability. However, the observed trend in real‐time operating systems (RTOSs) of progressively incorporating the POSIX interfaces have not reached the POSIX tracing services. As far as we know, this tracing interface has not been incorporated yet into any commercial RTOS, probably because it is quite recent and its tracing model is too complex and demanding for small, embedded real‐time systems. After carefully analyzing and then implementing and using the POSIX Trace standard in both RT‐Linux and MarteOS, this paper presents the redefinition of the POSIX tracing standard from the perspective of small real‐time systems and, in particular, systems conforming to the POSIX Minimal Realtime System Profile (MRSP). The new tracing model is called Lightweight POSIX tracing. The model has been carefully designed to maintain all the syntax, and almost all the semantics, of the original standard, but it allows for the definition of useful subsets of the original standard that can be implemented very efficiently. The experimental results show that a minimal tracing system which is appropriate for MRSP systems exhibits a significantly smaller memory footprint and lower overhead, compared to the implementation of the complete standard. Copyright © 2007 John Wiley & Sons, Ltd.     

An adaptive framework for monitoring agent organizations

Multiagent technologies are usually considered to be suitable for constructing agent organizations that are capable of running in dynamic and distributed environments and that are able to adapt to changes as the system runs. The necessary condition for this adaptation ability is to make agents aware of significant changes in both the environment and the organization. This paper presents mechanism, which helps agents detecting adaptation requirements dynamically at run time, and an Trace&Trigger, which is an adaptation framework for agent organizations. It consists of an event-tracing-based monitoring mechanism that provides organizational agents with information related to the costs and benefits of carrying out an adaptation process at each moment of the execution. This framework intends to overcome some of the problems that are present in other approaches by allowing the dynamic specification of the information that has to be retrieved by each agent at each moment for adaptation deliberation, avoiding the transference of useless information for adaptation deliberation. This framework has been integrated in the Magentix2 multiagent platform. In order to test its performance benefits for any agent organization, an example based on a market scenario is also presented.     

TRAMMAS: A tracing model for multiagent systems

Agent's flexibility and autonomy, as well as their capacity to coordinate and cooperate, are some of the features which make multiagent systems useful to work in dynamic and distributed environments. These key features are directly related to the way in which agents communicate and perceive each other, as well as their environment and surrounding conditions. Traditionally, this has been accomplished by means of message exchange or by using blackboard systems. These traditional methods have the advantages of being easy to implement and well supported by multiagent platforms; however, their main disadvantage is that the amount of social knowledge in the system directly depends on every agent actively informing of what it is doing, thinking, perceiving, etc. There are domains, for example those where social knowledge depends on highly distributed pieces of data provided by many different agents, in which such traditional methods can produce a great deal of overhead, hence reducing the scalability, efficiency and flexibility of the multiagent system. This work proposes the use of event tracing in multiagent systems, as an indirect interaction and coordination mechanism to improve the amount and quality of the information that agents can perceive from both their physical and social environment, in order to fulfill their goals more efficiently. In order to do so, this work presents an abstract model of a tracing system and an architectural design of such model, which can be incorporated to a typical multiagent platform.     

Flexible Real-Time Linux*: A Flexible Hard Real-Time Environment

This paper presents a framework appropriate for Flexible Real-Time Systems (FRTS) and a run-time support system based on that framework, called Flexible Real-Time Linux (FRTL). The framework proposes to build each task as a sequence of mandatory and optional components and to separate their execution in two scheduling levels. This approach is shown to provide both hard guarantees and flexible behavior. The FRTL system has been implemented by enhancing the original capabilities of Real-Time Linux (RT-Linux), while maintaining its predictability and efficiency features. This paper also shows a complete schedulability test on which all sources of overhead of the FRTL itself have been introduced. By applying this complete test, the designer is able to safely guarantee a real-time application running on the FRTL system.